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useradd – create a new user or update default new user information

 useradd OPTION USER
option
-s the login shell for the new user account

# useradd -s /sbin/nologin user
-d home directory for the new user account

# useradd -d /home/user user
-g force use GROUP for the new user account

# useradd -g group user
-e set account expiration date to EXPIRE_DATE

# useradd -e 20081231 user
-u force use the UID for the new user account

# useradd -u 550 user
-m create home directory for the new user account

# useradd -m user
-M do not create user’s home directory(overrides /etc/login.defs)

# useradd -M user
 
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Posted by on July 30, 2013 in Redhat & Cent OS

 

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Command Line Tools to Monitor Linux Performance

It’s really very tough job for every System or Network administrator to monitor and debugLinux System Performance problems every day. After being a Linux Administrator for 5 years in IT industry, I came to know that how hard is to monitor and keep systems up and running. For this reason, we’ve compiled the list of Top 15 frequently used command line monitoring tools that might be useful for every Linux/Unix System Administrator. These commands are available under all flavors of Linux and can be useful to monitor and find the actual causes of performance problem. This list of commands shown here are very enough for you to pick the one that is suitable for your monitoring scenario.

1. Top – Linux Process Monitoring

Linux Top command is a performance monitoring program which is used frequently by many system administrators to monitor Linux performance and it is available under many Linux/Unixlike operating systems. The top command used to dipslay all the running and active real-time processes in ordered list and updates it regularly. It display CPU usageMemory usageSwap MemoryCache SizeBuffer SizeProcess PIDUserCommands and much more. It also shows high memory and cpu utilization of a running processess. The top command is much userful for system administrator to monitor and take correct action when required. Let’s see top command in action.

# top
Top Command Example
Top Command Example

For more examples of Top command read : 12 TOP Command Examples in Linux

2. VmStat – Virtual Memory Statistics

Linux VmStat command used to display statistics of virtual memorykernerl threadsdisks,system processesI/O blocksinterruptsCPU activity and much more. By default vmstat command is not available under Linux systems you need to install a package called sysstat that includes a vmstat program. The common usage of command format is.

# vmstat

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free  inact active   si   so    bi    bo   in   cs us sy id wa st
 1  0      0 810420  97380  70628    0    0   115     4   89   79  1  6 90  3  0

For more Vmstat examples read : 6 Vmstat Command Examples in Linux

3. Lsof – List Open Files

Lsof command used in many Linux/Unix like system that is used to display list of all the open files and the processes. The open files included are disk filesnetwork socketspipes,devices and processes. One of the main reason for using this command is when a disk cannot be unmounted and displays the error that files are being used or opened. With this commmand you can easily identify which files are in use. The most common format for this command is.

# lsof

COMMAND     PID      USER   FD      TYPE     DEVICE     SIZE       NODE NAME
init          1      root  cwd       DIR      104,2     4096          2 /
init          1      root  rtd       DIR      104,2     4096          2 /
init          1      root  txt       REG      104,2    38652   17710339 /sbin/init
init          1      root  mem       REG      104,2   129900     196453 /lib/ld-2.5.so
init          1      root  mem       REG      104,2  1693812     196454 /lib/libc-2.5.so
init          1      root  mem       REG      104,2    20668     196479 /lib/libdl-2.5.so
init          1      root  mem       REG      104,2   245376     196419 /lib/libsepol.so.1
init          1      root  mem       REG      104,2    93508     196431 /lib/libselinux.so.1
init          1      root   10u     FIFO       0,17                 953 /dev/initctl

More lsof command usage and examples : 10 lsof Command Examples in Linux

4. Tcpdump – Network Packet Analyzer

Tcpdump one of the most widely used command-line network packet analyzer or packets sniffer program that is used capture or filter TCP/IP packets that received or transferred on a specific interface over a network. It also provides a option to save captured packages in a file for later analysis. tcpdump is almost available in all major Linux distributions.

# tcpdump -i eth0

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
22:08:59.617628 IP tecmint.com.ssh > 115.113.134.3.static-mumbai.vsnl.net.in.28472: P 2532133365:2532133481(116) ack 3561562349 win 9648
22:09:07.653466 IP tecmint.com.ssh > 115.113.134.3.static-mumbai.vsnl.net.in.28472: P 116:232(116) ack 1 win 9648
22:08:59.617916 IP 115.113.134.3.static-mumbai.vsnl.net.in.28472 > tecmint.com.ssh: . ack 116 win 64347

For more tcpdump usage read : 12 Tcpdump Command Examples in Linux

5. Netstat – Network Statistics

Netstat is a command line tool for monitoring incoming and outgoing network packets statistics as well as interface statistics. It is very useful tool for every system administrator to monitor network performance and troubleshoot network related problems.

# netstat -a | more

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address               Foreign Address             State
tcp        0      0 *:mysql                     *:*                         LISTEN
tcp        0      0 *:sunrpc                    *:*                         LISTEN
tcp        0      0 *:realm-rusd                *:*                         LISTEN
tcp        0      0 *:ftp                       *:*                         LISTEN
tcp        0      0 localhost.localdomain:ipp   *:*                         LISTEN
tcp        0      0 localhost.localdomain:smtp  *:*                         LISTEN
tcp        0      0 localhost.localdomain:smtp  localhost.localdomain:42709 TIME_WAIT
tcp        0      0 localhost.localdomain:smtp  localhost.localdomain:42710 TIME_WAIT
tcp        0      0 *:http                      *:*                         LISTEN
tcp        0      0 *:ssh                       *:*                         LISTEN
tcp        0      0 *:https                     *:*                         LISTEN

More Netstat examples : 20 Netstat Command Examples in Linux.

6. Htop – Linux Process Monitoring

Htop is a much advanced interactive and real time Linux process monitoring tool. This is much similar to Linux top command but it has some rich features like user friendly interface to manage processshortcut keysvertical and horizontal view of the processes and much more. Htop is a third party tool and doesn’t included in Linux systems, you need to install it using YUM package manager tool. For more information on installation read our article below.

# htop
Htop Command Example
Htop Command Example Screenshot

For Htop installation read : Install Htop (Linux Process Monitoring) in Linux

7. Iotop – Monitor Linux Disk I/O

Iotop is also much similar to top command and Htop program, but it has accounting function to monitor and display real time Disk I/O and processes. This tool is much useful for finding the exact process and high used disk read/writes of the processes.

# iotop
Iotop Command ExampleIotop Command Example Screenshot

For Ioptop installation and usage read : Install Iotop in Linux

8. Iostat – Input/Output Statistics

IoStat is simple tool that will collect and show system input and output storage device statistics. This tool is often used to trace storage device performance issues including deviceslocal disksremote disks such as NFS.

# iostat

Linux 2.6.18-238.9.1.el5 (tecmint.com)         09/13/2012

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2.60    3.65    1.04    4.29    0.00   88.42Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
cciss/c0d0       17.79       545.80       256.52  855159769  401914750
cciss/c0d0p1      0.00         0.00         0.00       5459       3518
cciss/c0d0p2     16.45       533.97       245.18  836631746  384153384
cciss/c0d0p3      0.63         5.58         3.97    8737650    6215544
cciss/c0d0p4      0.00         0.00         0.00          8          0
cciss/c0d0p5      0.63         3.79         5.03    5936778    7882528
cciss/c0d0p6      0.08         2.46         2.34    3847771    3659776

For more Iostat usage and examples visit : 6 Iostat Command Examples in Linux

9. IPTraf – Real Time IP LAN Monitoring

IPTraf is an open source console-based real time network (IP LAN) monitoring utility forLinux. It collects a variety of information such as IP traffic monitor that passes over the network, including TCP flag information, ICMP details, TCP/UDP traffic breakdowns, TCP connection packet and byne counts. It also gathers information of general and detaled interface statistics of TCP, UDP, IP, ICMP, non-IP, IP checksum errors, interface activity etc.

IP Traffic Monitor

For more information and usage of IPTraf tool, please visit : IPTraf Network Monitoring Tool

10. Psacct or Acct – Monitor User Activity

psacct or acct tools are very useful for monitoring each users activity on the system. Both daemons runs in the background and keeps a close watch on the overall activity of each user on the system and also what resources are being consumed by them.

These tools are very useful for system administrators to track each users activity like what they are doing, what commands they issued, how much resources are used by them, how long they are active on the system etc.

For installation and example usage of commands read the article on Monitor User Activity with psacct or acct

11. Monit – Linux Process and Services Monitoring

Monit is a free open source and web based process supervision utility that automatically monitors and managers system processes, programs, files, directories, permissions, checksums and filesystems.

It monitors services like Apache, MySQL, Mail, FTP, ProFTP, Nginx, SSH and so on. The system status can be viewed from the command line or using it own web interface.

Monit Linux Process Monitoring

Read More : Linux Process Monitoring with Monit

12. NetHogs – Monitor Per Process Network Bandwidth

NetHogs is an open source nice small program (similar to Linux top command) that keeps a tab on each process network activity on your system. It also keeps a track of real time network traffic bandwidth used by each program or application.

NetHogs Linux Bandwidth Monitoring

Read More : Monitor Linux Network Bandwidth Using NetHogs

13. iftop – Network Bandwidth Monitoring

iftop is another terminal-based free open source system monitoring utility that displays a frequently updated list of network bandwidth utilization (source and destination hosts) that passing through the network interface on your system. iftop is considered for network usage, what ‘top‘ does for CPU usage. iftop is a ‘top‘ family tool that monitor a selected interface and displays a current bandwidth usage between two hosts.

iftop - Network Bandwidth Monitoring

Read More : iftop – Monitor Network Bandwidth Utilization

14. Monitorix – System and Network Monitoring

Monitorix is a free lightweight utility that is designed to run and monitor system and network resources as many as possible in Linux/Unix servers. It has a built in HTTP web server that regularly collects system and network information and display them in graphs. It Monitorssystem load average and usagememory allocationdisk driver healthsystem servicesnetwork portsmail statistics (SendmailPostfixDovecot, etc), MySQL statistics and many more. It designed to monitor overall system performance and helps in detecting failures, bottlenecks, abnormal activities etc.

Monitorix Monitoring

Read More : Monitorix a System and Network Monitoring Tool for Linux

15. Arpwatch – Ethernet Activity Monitor

Arpwatch is a kind of program that is designed to monitor Address Resolution (MAC and IPaddress changes) of Ethernet network traffic on a Linux network. It continuously keeps watch on Ethernet traffic and produces a log of IP and MAC address pair changes along with a timestamps on a network. It also has a feature to send an email alerts to administrator, when a pairing added or changes. It is very useful in detecting ARP spoofing on a network.

Read More : Arpwatch to Monitor Ethernet Activity

We would like to know what kind of monitoring programs you use to monitor performance of your Linux servers? If we’ve missed any important tool that you would like us to include in this list, please inform us via comments and please don’t forget to share it.

 
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Posted by on August 21, 2013 in Unix & Linux

 

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Useful Commands for Linux

For a person new to Linux, finding Linux functional is still not very easy even after the emergence of user friendly Linux distribution like Ubuntu and Mint. The thing remains that there will always be some configuration on user’s part to be done manually.

Just to start with, the first thing a user should know is the basic commands in terminal. Linux GUI runs on Shell. When GUI is not running but Shell is running, Linux is running. If Shell is not running, nothing is running. Commands in Linux is a means of interaction with Shell. For a beginners some of the basic computational task is to:

  1. View the contents of a directory : A directory may contains visible and invisible files with different file permissions.
  2. Viewing blocks, HDD partition, External HDD
  3. Checking the integrity of Downloaded/Transferred Packages
  4. Converting and copying a file
  5. Know your machine name, OS and Kernel
  6. Viewing history
  7. Being root
  8. Make Directory
  9. Make Files
  10. Changing the file permission
  11. Own a file
  12. Install, Update and maintain Packages
  13. Uncompressing a file
  14. See current date, time and calendar
  15. Print contents of a file
  16. Copy and Move
  17. See the working directory for easy navigation
  18. Change the working directory, etc…

And we have described all of the above basic computational task in our First Article.

Part I – Switching From Windows to Nix or a Newbie to Linux – 20 Useful Commands for Linux Newbies

So you are planning to switch from Windows to Linux, or have just switched to Linux? Oops!!! what I am asking! For what else reason would you have been here. From my past experience when I was new to Nux, commands and terminal really scared me, I was worried about the commands, as to what extent I have to remember and memorise them to get myself fully functional with Linux. No doubt online documentation, books, man pages and user community helped me a lot but I strongly believed that there should be an article with details of commands in easy to learn and understand language.These Motivated me to Master Linux and to make it easy-to-use. My this article is a step towards it.

1. Command: ls

The command “ls” stands for (List Directory Contents), List the contents of the folder, be it file or folder, from which it runs.

root@tecmint:~# ls

Android-Games                     Music
Pictures                          Public
Desktop                           Tecmint.com
Documents                         TecMint-Sync
Downloads                         Templates

The command “ls -l” list the content of folder, in long listing fashion.

root@tecmint:~# ls -l

total 40588
drwxrwxr-x 2 ravisaive ravisaive     4096 May  8 01:06 Android Games
drwxr-xr-x 2 ravisaive ravisaive     4096 May 15 10:50 Desktop
drwxr-xr-x 2 ravisaive ravisaive     4096 May 16 16:45 Documents
drwxr-xr-x 6 ravisaive ravisaive     4096 May 16 14:34 Downloads
drwxr-xr-x 2 ravisaive ravisaive     4096 Apr 30 20:50 Music
drwxr-xr-x 2 ravisaive ravisaive     4096 May  9 17:54 Pictures
drwxrwxr-x 5 ravisaive ravisaive     4096 May  3 18:44 Tecmint.com
drwxr-xr-x 2 ravisaive ravisaive     4096 Apr 30 20:50 Templates

Command “ls -a“, list the content of folder, including hidden files starting with ‘.’.

root@tecmint:~# ls -a

.			.gnupg			.dbus			.goutputstream-PI5VVW		.mission-control
.adobe                  deja-dup                .grsync                 .mozilla                 	.themes
.gstreamer-0.10         .mtpaint                .thumbnails             .gtk-bookmarks          	.thunderbird
.HotShots               .mysql_history          .htaccess		.apport-ignore.xml      	.ICEauthority           
.profile                .bash_history           .icons                  .bash_logout                    .fbmessenger
.jedit                  .pulse                  .bashrc                 .liferea_1.8             	.pulse-cookie            
.Xauthority		.gconf                  .local                  .Xauthority.HGHVWW		.cache
.gftp                   .macromedia             .remmina                .cinnamon                       .gimp-2.8
.ssh                    .xsession-errors 	.compiz                 .gnome                          teamviewer_linux.deb          
.xsession-errors.old	.config                 .gnome2                 .zoncolor

Note: In Linux file name starting with ‘.‘ is hidden. In Linux every file/folder/device/command is a file. The output of ls -l is:

  1. d (stands for directory).
  2. rwxr-xr-x is the file permission of the file/folder for owner, group and world.
  3. The 1st ravisaive in the above example means that file is owned by user ravisaive.
  4. The 2nd ravisaive in the above example means file belongs to user group ravisaive.
  5. 4096 means file size is 4096 Bytes.
  6. May 8 01:06 is the date and time of last modification.
  7. And at the end is the name of the File/Folder.

For more “ls” command examples read 15 ‘ls’ Command Examples in Linux.

2. Command: lsblk

The “lsblk” stands for (List Block Devices), print block devices by their assigned name (but notRAM) on the standard output in a tree-like fashion.

root@tecmint:~# lsblk

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 232.9G  0 disk 
├─sda1   8:1    0  46.6G  0 part /
├─sda2   8:2    0     1K  0 part 
├─sda5   8:5    0   190M  0 part /boot
├─sda6   8:6    0   3.7G  0 part [SWAP]
├─sda7   8:7    0  93.1G  0 part /data
└─sda8   8:8    0  89.2G  0 part /personal
sr0     11:0    1  1024M  0 rom

The “lsblk -l” command list block devices in ‘list‘ structure (not tree like fashion).

root@tecmint:~# lsblk -l

NAME MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda    8:0    0 232.9G  0 disk 
sda1   8:1    0  46.6G  0 part /
sda2   8:2    0     1K  0 part 
sda5   8:5    0   190M  0 part /boot
sda6   8:6    0   3.7G  0 part [SWAP]
sda7   8:7    0  93.1G  0 part /data
sda8   8:8    0  89.2G  0 part /personal
sr0   11:0    1  1024M  0 rom

Note: lsblk is very useful and easiest way to know the name of New Usb Device you just plugged in, especially when you have to deal with disk/blocks in terminal.

3. Command: md5sum

The “md5sum” stands for (Compute and Check MD5 Message Digest), md5 checksum (commonly called hash) is used to match or verify integrity of files that may have changed as a result of a faulty file transfer, a disk error or non-malicious interference.

root@tecmint:~# md5sum teamviewer_linux.deb 

47790ed345a7b7970fc1f2ac50c97002  teamviewer_linux.deb

Note: The user can match the generated md5sum with the one provided officially. Md5sum is considered less secure than sha1sum, which we will discuss later.

4. Command: dd

Command “dd” stands for (Convert and Copy a file), Can be used to convert and copy a file and most of the times is used to copy a iso file (or any other file) to a usb device (or any other location), thus can be used to make a ‘Bootlable‘ Usb Stick.

root@tecmint:~# dd if=/home/user/Downloads/debian.iso of=/dev/sdb1 bs=512M; sync

Note: In the above example the usb device is supposed to be sdb1 (You should Verify it using command lsblk, otherwise you will overwrite your disk and OS), use name of disk very Cautiously!!!.

dd command takes some time ranging from a few seconds to several minutes in execution, depending on the size and type of file and read and write speed of Usb stick.

5. Command: uname

The “uname” command stands for (Unix Name), print detailed information about the machine name, Operating System and Kernel.

root@tecmint:~# uname -a

Linux tecmint 3.8.0-19-generic #30-Ubuntu SMP Wed May 1 16:36:13 UTC 2013 i686 i686 i686 GNU/Linux

Note: uname shows type of kernel. uname -a output detailed information. Elaborating the above output of uname -a.

  1. Linux“: The machine’s kernel name.
  2. tecmint“: The machine’s node name.
  3. 3.8.0-19-generic“: The kernel release.
  4. #30-Ubuntu SMP“: The kernel version.
  5. i686“: The architecture of the processor.
  6. GNU/Linux“: The operating system name.

6. Command: history

The “history” command stands for History (Event) Record, it prints the history of long list of executed commands in terminal.

root@tecmint:~# history

 1  sudo add-apt-repository ppa:tualatrix/ppa
 2  sudo apt-get update
 3  sudo apt-get install ubuntu-tweak
 4  sudo add-apt-repository ppa:diesch/testing
 5  sudo apt-get update
 6  sudo apt-get install indicator-privacy
 7  sudo add-apt-repository ppa:atareao/atareao
 8  sudo apt-get update
 9  sudo apt-get install my-weather-indicator
 10 pwd
 11 cd && sudo cp -r unity/6 /usr/share/unity/
 12 cd /usr/share/unity/icons/
 13 cd /usr/share/unity

Note: Pressing “Ctrl + R” and then search for already executed commands which lets your command to be completed with auto completion feature.

(reverse-i-search)`if': ifconfig

7. Command: sudo

The “sudo” (super user do) command allows a permitted user to execute a command as the superuser or another user, as specified by the security policy in the sudoers list.

root@tecmint:~# sudo add-apt-repository ppa:tualatrix/ppa

Note: sudo allows user to borrow superuser privileged, while a similar command ‘su‘ allows user to actually log in as superuser. Sudo is safer than su.
It is not advised to use sudo or su for day-to-day normal use, as it can result in serious error if accidentally you did something wrong, that’s why a very popular saying in Linux community is:

“To err is human, but to really foul up everything, you need root password.”

8. Command: mkdir

The “mkdir” (Make directory) command create a new directory with name path. However is the directory already exists, it will return an error message “cannot create folder, folder already exists”.

root@tecmint:~# mkdir tecmint

Note: Directory can only be created inside the folder, in which the user has write permission.mkdir: cannot create directory `tecmint‘: File exists
(Don’t confuse with file in the above output, you might remember what i said at the beginning – In Linux every file, folder, drive, command, scripts are treated as file).

9. Command: touch

The “touch” command stands for (Update the access and modification times of each FILE to the current time). touch command creates the file, only if it doesn’t exist. If the file already exists it will update the timestamp and not the contents of the file.

root@tecmint:~# touch tecmintfile

Note: touch can be used to create file under directory, on which the user has write permission, only if the file don’t exist there.

10. Command: chmod

The Linux “chmod” command stands for (change file mode bits). chmod changes the file mode (permission) of each given file, folder, script, etc.. according to mode asked for.

There exist 3 types of permission on a file (folder or anything but to keep things simple we will be using file).

Read (r)=4
Write(w)=2
Execute(x)=1

So if you want to give only read permission on a file it will be assigned a value of ‘4‘, for write permission only, a value of ‘2‘ and for execute permission only, a value of ‘1‘ is to be given. For read and write permission 4+2 = ‘6‘ is to be given, ans so on.

Now permission need to be set for 3 kinds of user and usergroup. The first is owner, then usergroup and finally world.

rwxr-x--x   abc.sh

Here the root’s permission is rwx (readwrite and execute).
usergroup to which it belongs, is r-x (read and execute only, no write permission) and
for world is –x (only execute).

To change its permission and provide readwrite and execute permission to owner, group and world.

root@tecmint:~# chmod 777 abc.sh

only read and write permission to all three.

root@tecmint:~# chmod 666 abc.sh

readwrite and execute to owner and only execute to group and world.

root@tecmint:~# chmod 711 abc.sh

Note: one of the most important command useful for sysadmin and user both. On a multi-user environment or on a server, this command comes to rescue, setting wrong permission will either makes a file inaccessible or provide unauthorized access to someone.

11. Command: chown

The Linux “chown” command stands for (change file owner and group). Every file belongs to a group of user and a owner. It is used Do ‘ls -l‘ into your directory and you will see something like this.

root@tecmint:~# ls -l 

drwxr-xr-x 3 server root 4096 May 10 11:14 Binary 
drwxr-xr-x 2 server server 4096 May 13 09:42 Desktop

Here the directory Binary is owned by user “server” and it belongs to usergroup “root” where as directory “Desktop” is owned by user “server” and belongs to user group “server“.

This “chown” command is used to change the file ownership and thus is useful in managing and providing file to authorised user and usergroup only.

root@tecmint:~# chown server:server Binary

drwxr-xr-x 3 server server 4096 May 10 11:14 Binary 
drwxr-xr-x 2 server server 4096 May 13 09:42 Desktop

Note: “chown” changes the user and group ownership of each given FILE to NEW-OWNER or to the user and group of an existing reference file.

12. Command: apt

The Debian based “apt” command stands for (Advanced Package Tool). Apt is an advanced package manager for Debian based system (UbuntuKubuntu, etc.), that automatically and intelligently searchinstallupdate and resolves dependency of packages on Gnu/Linuxsystem from command line.

root@tecmint:~# apt-get install mplayer

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following package was automatically installed and is no longer required:
  java-wrappers
Use 'apt-get autoremove' to remove it.
The following extra packages will be installed:
  esound-common libaudiofile1 libesd0 libopenal-data libopenal1 libsvga1 libvdpau1 libxvidcore4
Suggested packages:
  pulseaudio-esound-compat libroar-compat2 nvidia-vdpau-driver vdpau-driver mplayer-doc netselect fping
The following NEW packages will be installed:
  esound-common libaudiofile1 libesd0 libopenal-data libopenal1 libsvga1 libvdpau1 libxvidcore4 mplayer
0 upgraded, 9 newly installed, 0 to remove and 8 not upgraded.
Need to get 3,567 kB of archives.
After this operation, 7,772 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
root@tecmint:~# apt-get update

Hit http://ppa.launchpad.net raring Release.gpg                                           
Hit http://ppa.launchpad.net raring Release.gpg                                           
Hit http://ppa.launchpad.net raring Release.gpg                      
Hit http://ppa.launchpad.net raring Release.gpg                      
Get:1 http://security.ubuntu.com raring-security Release.gpg [933 B] 
Hit http://in.archive.ubuntu.com raring Release.gpg                                                   
Hit http://ppa.launchpad.net raring Release.gpg                      
Get:2 http://security.ubuntu.com raring-security Release [40.8 kB]   
Ign http://ppa.launchpad.net raring Release.gpg                                                  
Get:3 http://in.archive.ubuntu.com raring-updates Release.gpg [933 B]                            
Hit http://ppa.launchpad.net raring Release.gpg                                                                
Hit http://in.archive.ubuntu.com raring-backports Release.gpg

Note: The above commands results into system-wide changes and hence requires root password (Check ‘#‘ and not ‘$’ as prompt). Apt is considered more advanced and intelligent as compared to yum command.

As the name suggest, apt-cache search for package containing sub package mpalyerapt-getinstall, update all the packages, that are already installed, to the newest one.

Read more about apt-get and apt-cache commands at 25 APT-GET and APT-CACHE Commands

13. Command: tar

The “tar” command is a Tape Archive is useful in creation of archive, in a number of file format and their extraction.

root@tecmint:~# tar -zxvf abc.tar.gz (Remember 'z' for .tar.gz)
root@tecmint:~# tar -jxvf abc.tar.bz2 (Remember 'j' for .tar.bz2)
root@tecmint:~# tar -cvf archieve.tar.gz(.bz2) /path/to/folder/abc

Note: A ‘tar.gz‘ means gzipped. ‘tar.bz2‘ is compressed with bzip which uses a better but slower compression method.

Read more about “tar command” examples at 18 Tar Command Examples

14. Command: cal

The “cal” (Calendar), it is used to displays calendar of the present month or any other month of any year that is advancing or passed.

root@tecmint:~# cal 

May 2013        
Su Mo Tu We Th Fr Sa  
          1  2  3  4  
 5  6  7  8  9 10 11  
12 13 14 15 16 17 18  
19 20 21 22 23 24 25  
26 27 28 29 30 31

Show calendar of year 1835 for month February, that already has passed.

root@tecmint:~# cal 02 1835

   February 1835      
Su Mo Tu We Th Fr Sa  
 1  2  3  4  5  6  7  
 8  9 10 11 12 13 14  
15 16 17 18 19 20 21  
22 23 24 25 26 27 28

Shows calendar of year 2145 for the month of July, that will advancing

root@tecmint:~# cal 07 2145

     July 2145        
Su Mo Tu We Th Fr Sa  
             1  2  3  
 4  5  6  7  8  9 10  
11 12 13 14 15 16 17  
18 19 20 21 22 23 24  
25 26 27 28 29 30 31

Note: You need not to turn the calendar of 50 years back, neither you need to make complex mathematical calculation to know what day you were worn or your coming birthday will fall on which day.

15. Command: date

The “date” (Date) command print the current date and time on the standard output, and can further be set.

root@tecmint:~# date

Fri May 17 14:13:29 IST 2013
root@tecmint:~# date --set='14 may 2013 13:57' 

Mon May 13 13:57:00 IST 2013

Note: This Command will be very use-full in scripting, time and date based scripting, to be more perfect. Moreover changing date and time using terminal will make you feel GEEK!!!. (Obviously you need to be root to perform this operation, as it is a system wide change).

16. Command: cat

The “cat” stands for (Concatenation). Concatenate (join) two or more plain file and/or print contents of a file on standard output.

root@tecmint:~# cat a.txt b.txt c.txt d.txt abcd.txt
root@tecmint:~# cat abcd.txt
....
contents of file abcd
...

Note: “>>” and “>” are called append symbol. They are used to append the output to a file and not on standard output. “>” symbol will delete a file already existed and create a new file hence for security reason it is advised to use “>>” that will write the output without overwriting or deleting the file.

Before Proceeding further, I must let you know about wildcards (you would be aware of wildcard entry, in most of the Television shows) Wildcards are a shell feature that makes the command line much more powerful than any GUI file managers. You see, if you want to select a big group of files in a graphical file manager, you usually have to select them with your mouse. This may seem simple, but in some cases it can be very frustrating.

For example, suppose you have a directory with a huge amount of all kinds of files and subdirectories, and you decide to move all the HTML files, that have the word “Linux” somewhere in the middle of their names, from that big directory into another directory. What’s a simple way to do this? If the directory contains a huge amount of differently named HTML files, your task is everything but simple!

In the Linux CLI that task is just as simple to perform as moving only one HTML file, and it’s so easy because of the shell wildcards. These are special characters that allow you to select file names that match certain patterns of characters. This helps you to select even a big group of files with typing just a few characters, and in most cases it’s easier than selecting the files with a mouse.

Here’s a list of the most commonly used wildcards :

Wildcard			Matches
   *			zero or more characters
   ?			exactly one character
[abcde]			exactly one character listed
 [a-e]			exactly one character in the given range
[!abcde]		any character that is not listed
 [!a-e]			any character that is not in the given range
{debian,linux}		exactly one entire word in the options given

! is called not symbol, and the reverse of string attached with ‘!’ is true.

Read more examples of Linux “cat command” at 13 Cat Command Examples in Linux

17. Command: cp

The “copy” stands for (Copy), it copies a file from one location to another location.

root@tecmint:~# cp /home/user/Downloads abc.tar.gz /home/user/Desktop (Return 0 when sucess)

Note: cp is one of the most commonly used command in shell scripting and it can be used with wildcard characters (Describe in the above block), for customised and desired file copying.

18. Command: mv

The “mv” command moves a file from one location to another location.

root@tecmint:~# mv /home/user/Downloads abc.tar.gz /home/user/Desktop (Return 0 when sucess)

Note: mv command can be used with wildcard characters. mv should be used with caution, as moving of system/unauthorised file may lead to security as well as breakdown of system.

19. Command: pwd

The command “pwd” (print working directory), prints the current working directory with full path name from terminal.

root@tecmint:~# pwd 

/home/user/Desktop

Note: This command won’t be much frequently used in scripting but it is an absolute life saver for newbie who gets lost in terminal in their early connection with nux. (Linux is most commonly referred as nux or nix).

20. Command: cd

Finally, the frequently used “cd” command stands for (change directory), it change the working directory to execute, copy, move write, read, etc. from terminal itself.

root@tecmint:~# cd /home/user/Desktop
server@localhost:~$ pwd

/home/user/Desktop

Note: cd comes to rescue when switching between directories from terminal. “Cd ~” will change the working directory to user’s home directory, and is very useful if a user finds himself lost in terminal. “Cd ..” will change the working directory to parent directory (of current working directory).

These commands will surely make you comfortable with Linux. But it’s not the end. Very soon I will be coming with other commands which will be useful for ‘Middle Level User‘ i.e., You! No don’t exclaim, if you get used-to these commands, You will notice promotion in user-level fromnewbie to Middle-level-user. In the next article, I will be coming up with commands like ‘Kill‘, ‘Ps‘, ‘grep‘,….Wait for the article and I don’t want to spoil your interest.

Part II – 20 Advanced Commands for Middle Level Linux Users

You might have found the first article very much useful, this article is an extension of the 20 Useful Commands for Linux Newbies. The first article was intended for newbies and this article is for Middle-Level-User and Advanced Users. Here you will find how to customise search, know the processes running guide to kill them, how to make your Linux terminal productive is an important aspect and how to compile cc++java programs in nix.

21. Command: Find

Search for files in the given directory, hierarchically starting at the parent directory and moving to sub-directories.

root@tecmint:~# find -name *.sh 

./Desktop/load.sh 
./Desktop/test.sh 
./Desktop/shutdown.sh 
./Binary/firefox/run-mozilla.sh 
./Downloads/kdewebdev-3.5.8/quanta/scripts/externalpreview.sh 
./Downloads/kdewebdev-3.5.8/admin/doxygen.sh 
./Downloads/kdewebdev-3.5.8/admin/cvs.sh 
./Downloads/kdewebdev-3.5.8/admin/ltmain.sh 
./Downloads/wheezy-nv-install.sh

Note: The `-name‘ option makes the search case sensitive. You can use the `-iname‘ option to find something regardless of case. (* is a wildcard and searches all the file having extension ‘.sh‘ you can use filename or a part of file name to customise the output).

root@tecmint:~# find -iname *.SH ( find -iname *.Sh /  find -iname *.sH)

./Desktop/load.sh 
./Desktop/test.sh 
./Desktop/shutdown.sh 
./Binary/firefox/run-mozilla.sh 
./Downloads/kdewebdev-3.5.8/quanta/scripts/externalpreview.sh 
./Downloads/kdewebdev-3.5.8/admin/doxygen.sh 
./Downloads/kdewebdev-3.5.8/admin/cvs.sh 
./Downloads/kdewebdev-3.5.8/admin/ltmain.sh 
./Downloads/wheezy-nv-install.sh
root@tecmint:~# find -name *.tar.gz 

/var/www/modules/update/tests/aaa_update_test.tar.gz 
./var/cache/flashplugin-nonfree/install_flash_player_11_linux.i386.tar.gz 
./home/server/Downloads/drupal-7.22.tar.gz 
./home/server/Downloads/smtp-7.x-1.0.tar.gz 
./home/server/Downloads/noreqnewpass-7.x-1.2.tar.gz 
./usr/share/gettext/archive.git.tar.gz 
./usr/share/doc/apg/php.tar.gz 
./usr/share/doc/festival/examples/speech_pm_1.0.tar.gz 
./usr/share/doc/argyll/examples/spyder2.tar.gz 
./usr/share/usb_modeswitch/configPack.tar.gz

Note: The above command searches for all the file having extension ‘tar.gz‘ in root directory and all the sub-directories including mounted devices.

Read more examples of Linux ‘find‘ command at 35 Find Command Examples in Linux

22. Command: grep

The ‘grep‘ command searches the given file for lines containing a match to the given strings or words. Search ‘/etc/passwd‘ for ‘tecmint‘ user.

root@tecmint:~# grep tecmint /etc/passwd 

tecmint:x:1000:1000:Tecmint,,,:/home/tecmint:/bin/bash

Ignore word case and all other combination with ‘-i‘ option.

root@tecmint:~# grep -i TECMINT /etc/passwd 

tecmint:x:1000:1000:Tecmint,,,:/home/tecmint:/bin/bash

Search recursively (-ri.e. read all files under each directory for a string “127.0.0.1“.

root@tecmint:~# grep -r "127.0.0.1" /etc/ 

/etc/vlc/lua/http/.hosts:127.0.0.1
/etc/speech-dispatcher/modules/ivona.conf:#IvonaServerHost "127.0.0.1"
/etc/mysql/my.cnf:bind-address		= 127.0.0.1
/etc/apache2/mods-available/status.conf:    Allow from 127.0.0.1 ::1
/etc/apache2/mods-available/ldap.conf:    Allow from 127.0.0.1 ::1
/etc/apache2/mods-available/info.conf:    Allow from 127.0.0.1 ::1
/etc/apache2/mods-available/proxy_balancer.conf:#    Allow from 127.0.0.1 ::1
/etc/security/access.conf:#+ : root : 127.0.0.1
/etc/dhcp/dhclient.conf:#prepend domain-name-servers 127.0.0.1;
/etc/dhcp/dhclient.conf:#  option domain-name-servers 127.0.0.1;
/etc/init/network-interface.conf:	ifconfig lo 127.0.0.1 up || true
/etc/java-6-openjdk/net.properties:# localhost & 127.0.0.1).
/etc/java-6-openjdk/net.properties:# http.nonProxyHosts=localhost|127.0.0.1
/etc/java-6-openjdk/net.properties:# localhost & 127.0.0.1).
/etc/java-6-openjdk/net.properties:# ftp.nonProxyHosts=localhost|127.0.0.1
/etc/hosts:127.0.0.1	localhost

Note: You can use these following options along with grep.

  1. -w for word (egrep -w ‘word1|word2‘ /path/to/file).
  2. -c for count (i.e., total number of times the pattern matched) (grep -c ‘word‘ /path/to/file).
  3. –color for coloured output (grep –color server /etc/passwd).

23. Command: man

The ‘man‘ is the system’s manual pager. Man provides online documentation for all the possible options with a command and its usages. Almost all the command comes with their corresponding manual pages. For example,

root@tecmint:~# man man

MAN(1)                                                               Manual pager utils                                                              MAN(1)

NAME
       man - an interface to the on-line reference manuals

SYNOPSIS
       man  [-C  file]  [-d]  [-D]  [--warnings[=warnings]]  [-R  encoding]  [-L  locale]  [-m  system[,...]]  [-M  path]  [-S list] [-e extension] [-i|-I]
       [--regex|--wildcard] [--names-only] [-a] [-u] [--no-subpages] [-P pager] [-r prompt] [-7] [-E encoding] [--no-hyphenation] [--no-justification]  [-p
       string] [-t] [-T[device]] [-H[browser]] [-X[dpi]] [-Z] [[section] page ...] ...
       man -k [apropos options] regexp ...
       man -K [-w|-W] [-S list] [-i|-I] [--regex] [section] term ...
       man -f [whatis options] page ...
       man -l [-C file] [-d] [-D] [--warnings[=warnings]] [-R encoding] [-L locale] [-P pager] [-r prompt] [-7] [-E encoding] [-p string] [-t] [-T[device]]
       [-H[browser]] [-X[dpi]] [-Z] file ...
       man -w|-W [-C file] [-d] [-D] page ...
       man -c [-C file] [-d] [-D] page ...
       man [-hV]

Manual page for man page itself, similarly ‘man cat‘ (Manual page for cat command) and ‘man ls‘ (Manual page for command ls).

Note: man page is intended for command reference and learning.

24. Command: ps

ps (Process) gives the status of running processes with a unique Id called PID.

root@tecmint:~# ps

 PID TTY          TIME CMD
 4170 pts/1    00:00:00 bash
 9628 pts/1    00:00:00 ps

To list status of all the processes along with process id and PID, use option ‘-A‘.

root@tecmint:~# ps -A

 PID TTY          TIME CMD
    1 ?        00:00:01 init
    2 ?        00:00:00 kthreadd
    3 ?        00:00:01 ksoftirqd/0
    5 ?        00:00:00 kworker/0:0H
    7 ?        00:00:00 kworker/u:0H
    8 ?        00:00:00 migration/0
    9 ?        00:00:00 rcu_bh
....

Note: This command is very useful when you want to know which processes are running or may need PID sometimes, for process to be killed. You can use it with ‘grep‘ command to find customised output. For example,

root@tecmint:~# ps -A | grep -i ssh

 1500 ?        00:09:58 sshd
 4317 ?        00:00:00 sshd

Here ‘ps‘ is pipelined with ‘grep‘ command to find customised and relevant output of our need.

25. Command: kill

OK, you might have understood what this command is for, from the name of the command. This command is used to kill process which is not relevant now or is not responding. It is very useful command, rather a very very useful command. You might be familiar with frequent windows restarting because of the fact that most of the time a running process can’t be killed, and if killed it needs windows to get restart so that changes could be taken into effect but in the world of Linux, there is no such things. Here you can kill a process and start it without restarting the whole system.

You need a process’s pid (ps) to kill it.

Let suppose you want to kill program ‘apache2‘ that might not be responding. Run ‘ps -A‘ along with grep command.

root@tecmint:~# ps -A | grep -i apache2

1285 ?        00:00:00 apache2

Find process ‘apache2‘, note its pid and kill it. For example, in my case ‘apache2‘ pid is ‘1285‘.

root@tecmint:~# kill 1285 (to kill the process apache2)

Note: Every time you re-run a process or start a system, a new pid is generated for each process and you can know about the current running processes and its pid using command ‘ps‘.

Another way to kill the same process is.

root@tecmint:~# pkill apache2

Note: Kill requires job id / process id for sending signals, where as in pkill, you have an option of using pattern, specifying process owner, etc.

26. Command: whereis

The ‘whereis‘ command is used to locate the BinarySources and Manual Pages of the command. For example, to locate the BinarySources and Manual Pages of the command ‘ls‘ and ‘kill‘.

root@tecmint:~# whereis ls 

ls: /bin/ls /usr/share/man/man1/ls.1.gz
root@tecmint:~# whereis kill

kill: /bin/kill /usr/share/man/man2/kill.2.gz /usr/share/man/man1/kill.1.gz

Note: This is useful to know where the binaries are installed for manual editing sometimes.

27. Command: service

The ‘service‘ command controls the StartingStopping or Restarting of a ‘service‘. This command make it possible to startrestart or stop a service without restarting the system, for the changes to be taken into effect.

Startting an apache2 server on Ubuntu

root@tecmint:~# service apache2 start

 * Starting web server apache2                                                                                                                                 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
httpd (pid 1285) already running						[ OK ]

Restarting a apache2 server on Ubuntu

root@tecmint:~# service apache2 restart

* Restarting web server apache2                                                                                                                               apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
 ... waiting .apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName  [ OK ]

Stopping a apache2 server on Ubuntu

root@tecmint:~# service apache2 stop

 * Stopping web server apache2                                                                                                                                 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
 ... waiting                                                           		[ OK ]

Note: All the process script lies in ‘/etc/init.d‘, and the path might needs to be included on certain system, i.e., in spite of running “service apache2 start” you would be asked to run “service /etc/init.d/apache2 start”.

28. Command: alias

alias is a built in shell command that lets you assign name for a long command or frequently used command.

I uses ‘ls -l‘ command frequently, which includes 5 characters including space. Hence I created an alias for this to ‘l‘.

root@tecmint:~# alias l='ls -l'

check if it works or not.

root@tecmint:~# l

total 36 
drwxr-xr-x 3 tecmint tecmint 4096 May 10 11:14 Binary 
drwxr-xr-x 3 tecmint tecmint 4096 May 21 11:21 Desktop 
drwxr-xr-x 2 tecmint tecmint 4096 May 21 15:23 Documents 
drwxr-xr-x 8 tecmint tecmint 4096 May 20 14:56 Downloads 
drwxr-xr-x 2 tecmint tecmint 4096 May  7 16:58 Music 
drwxr-xr-x 2 tecmint tecmint 4096 May 20 16:17 Pictures 
drwxr-xr-x 2 tecmint tecmint 4096 May  7 16:58 Public 
drwxr-xr-x 2 tecmint tecmint 4096 May  7 16:58 Templates 
drwxr-xr-x 2 tecmint tecmint 4096 May  7 16:58 Videos

To remove alias ‘l‘, use the following ‘unalias‘ command.

root@tecmint:~# unalias l

check, if ‘l‘ still is alias or not.

root@tecmint:~# l

bash: l: command not found

Making a little fun out of this command. Make alias of certain important command to some other important command.

alias cd='ls -l' (set alias of ls -l to cd)
alias su='pwd' (set alias of pwd to su)
....
(You can create your own)
....

Now when your friend types ‘cd‘, just think how funny it would be when he gets directory listing and not directory changing. And when he tries to be ‘su‘ the all he gets is the location of working directory. You can remove the alias later using command ‘unalias‘ as explained above.

29. Command: df

Report disk usages of file system. Useful for user as well as System Administrator to keep track of their disk usages. ‘df‘ works by examining directory entries, which generally are updated only when a file is closed.

root@tecmint:~# df

Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda1       47929224 7811908  37675948  18% /
none                   4       0         4   0% /sys/fs/cgroup
udev             1005916       4   1005912   1% /dev
tmpfs             202824     816    202008   1% /run
none                5120       0      5120   0% /run/lock
none             1014120     628   1013492   1% /run/shm
none              102400      44    102356   1% /run/user
/dev/sda5         184307   79852     94727  46% /boot
/dev/sda7       95989516   61104  91045676   1% /data
/dev/sda8       91953192   57032  87218528   1% /personal

For more examples of ‘df‘ command, read the article 12 df Command Examples in Linux.

30. Command: du

Estimate file space usage. Output the summary of disk usages by ever file hierarchically, i.e., in recursive manner.

root@tecmint:~# du

8       ./Daily Pics/wp-polls/images/default_gradient
8       ./Daily Pics/wp-polls/images/default
32      ./Daily Pics/wp-polls/images
8       ./Daily Pics/wp-polls/tinymce/plugins/polls/langs
8       ./Daily Pics/wp-polls/tinymce/plugins/polls/img
28      ./Daily Pics/wp-polls/tinymce/plugins/polls
32      ./Daily Pics/wp-polls/tinymce/plugins
36      ./Daily Pics/wp-polls/tinymce
580     ./Daily Pics/wp-polls
1456    ./Daily Pics
36      ./Plugins/wordpress-author-box
16180   ./Plugins
12      ./May Articles 2013/Xtreme Download Manager
4632    ./May Articles 2013/XCache

Note: ‘df‘ only reports usage statistics on file systems, while ‘du‘, on the other hand, measures directory contents. For more ‘du‘ command examples and usage, read 10 du (Disk Usage) Commands.

31. Command: rm

The command ‘rm‘ stands for remove. rm is used to remove files (s) and directories.

Removing a directory

root@tecmint:~# rm PassportApplicationForm_Main_English_V1.0

rm: cannot remove `PassportApplicationForm_Main_English_V1.0': Is a directory

The directory can’t be removed simply by ‘rm‘ command, you have to use ‘-rf‘ switch along with ‘rm‘.

root@tecmint:~# rm -rf PassportApplicationForm_Main_English_V1.0

Warning: “rm -rf” command is a destructive command if accidently you make it to the wrong directory. Once you ‘rm -rf‘ a directory all the files and the directory itself is lost forever, all of a sudden. Use it with caution.

32. Command: echo

echo as the name suggest echoes a text on the standard output. It has nothing to do with shell, nor does shell reads the output of echo command. However in an interactive script, echo passes the message to the user through terminal. It is one of the command that is commonly used in scripting, interactive scripting.

root@tecmint:~# echo "Tecmint.com is a very good website" 

Tecmint.com is a very good website
creating a small interactive script

1. create a file, named ‘interactive_shell.sh‘ on desktop. (Remember ‘.sh‘ extension is must).
2. copy and paste the below script, exactly same, as below.

#!/bin/bash 
echo "Please enter your name:" 
   read name 
   echo "Welcome to Linux $name"

Next, set execute permission and run the script.

root@tecmint:~# chmod 777 interactive_shell.sh
root@tecmint:~# ./interactive_shell.sh

Please enter your name:
Ravi Saive
Welcome to Linux Ravi Saive

Note: ‘#!/bin/bash‘ tells the shell that it is an script an it is always a good idea to include it at the top of script. ‘read‘ reads the given input.

33. Command: passwd

This is an important command that is useful for changing own password in terminal. Obviously you need to know your current passowrd for Security reason.

root@tecmint:~# passwd 

Changing password for tecmint. 
(current) UNIX password: ******** 
Enter new UNIX password: ********
Retype new UNIX password: ********
Password unchanged   [Here was passowrd remians unchanged, i.e., new password=old password]
Enter new UNIX password: #####
Retype new UNIX password:#####

34. Command: lpr

This command print files named on command line, to named printer.

root@tecmint:~# lpr -P deskjet-4620-series 1-final.pdf

Note: The ‘lpq‘ command lets you view the status of a printer (whether it’s up or not), and the jobs (files) waiting to be printed.

35. Command: cmp

compare two files of any type and writes the results to the standard output. By default, ‘cmp‘ Returns 0 if the files are the same; if they differ, the byte and line number at which the first difference occurred is reported.

To provide examples for this command, lets consider two files:

file1.txt
root@tecmint:~# cat file1.txt

Hi My name is Tecmint
file2.txt
root@tecmint:~# cat file2.txt

Hi My name is tecmint [dot] com

Now, let’s compare two files and see output of the command.

root@tecmint:~# cmp file1.txt file2.txt 

file1.txt file2.txt differ: byte 15, line 1

36. Command: wget

Wget is a free utility for non-interactive (i.e., can work in background) download of files from the Web. It supports HTTPHTTPSFTP protocols and HTTP proxies.

Download ffmpeg using wget

root@tecmint:~# wget http://downloads.sourceforge.net/project/ffmpeg-php/ffmpeg-php/0.6.0/ffmpeg-php-0.6.0.tbz2

--2013-05-22 18:54:52--  http://downloads.sourceforge.net/project/ffmpeg-php/ffmpeg-php/0.6.0/ffmpeg-php-0.6.0.tbz2
Resolving downloads.sourceforge.net (downloads.sourceforge.net)... 216.34.181.59
Connecting to downloads.sourceforge.net (downloads.sourceforge.net)|216.34.181.59|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://kaz.dl.sourceforge.net/project/ffmpeg-php/ffmpeg-php/0.6.0/ffmpeg-php-0.6.0.tbz2 [following]
--2013-05-22 18:54:54--  http://kaz.dl.sourceforge.net/project/ffmpeg-php/ffmpeg-php/0.6.0/ffmpeg-php-0.6.0.tbz2
Resolving kaz.dl.sourceforge.net (kaz.dl.sourceforge.net)... 92.46.53.163
Connecting to kaz.dl.sourceforge.net (kaz.dl.sourceforge.net)|92.46.53.163|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 275557 (269K) [application/octet-stream]
Saving to: ‘ffmpeg-php-0.6.0.tbz2’

100%[===========================================================================>] 2,75,557    67.8KB/s   in 4.0s   

2013-05-22 18:55:00 (67.8 KB/s) - ‘ffmpeg-php-0.6.0.tbz2’ saved [275557/275557]

37. Command: mount

Mount is an important command which is used to mount a filesystem that don’t mount itself. You need root permission to mount a device.

First run ‘lsblk‘ after plugging-in your filesystem and identify your device and note down you device assigned name.

root@tecmint:~# lsblk 

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT 
sda      8:0    0 931.5G  0 disk 
├─sda1   8:1    0 923.6G  0 part / 
├─sda2   8:2    0     1K  0 part 
└─sda5   8:5    0   7.9G  0 part [SWAP] 
sr0     11:0    1  1024M  0 rom  
sdb      8:16   1   3.7G  0 disk 
└─sdb1   8:17   1   3.7G  0 part

From this screen it was clear that I plugged in a 4 GB pendrive thus ‘sdb1‘ is my filesystem to be mounted. Become a root to perform this operation and change to /dev directory where all the file system is mounted.

root@tecmint:~# su
Password:
root@tecmint:~# cd /dev

Create a directory named anything but should be relevent for reference.

root@tecmint:~# mkdir usb

Now mount filesystem ‘sdb1‘ to directory ‘usb‘.

root@tecmint:~# mount /dev/sdb1 /dev/usb

Now you can navigate to /dev/usb from terminal or X-windows system and acess file from the mounted directory.

Time for Code Developer to know how rich Linux environment is

38. Command: gcc

gcc is the in-built compiler for ‘c‘ language in Linux Environment. A simple c program, save it on ur desktop as Hello.c (remember ‘.c‘ extension is must).

#include <stdio.h>
int main()
{
  printf("Hello world\n");
  return 0;
}
Compile it
root@tecmint:~# gcc Hello.c
Run it
root@tecmint:~# ./a.out 

Hello world

Note: On compiling a c program the output is automatically generated to a new file “a.out” and everytime you compile a c program same file “a.out” gets modified. Hence it is a good advice to define a output file during compile and thus there is no risk of overwrite to output file.

Compile it this way
root@tecmint:~# gcc -o Hello Hello.c

Here ‘-o‘ sends the output to ‘Hello‘ file and not ‘a.out‘. Run it again.

root@tecmint:~# ./Hello 

Hello world

39. Command: g++

g++ is the in-built compiler for ‘C++‘ , the first object oriented programming language. A simplec++ program, save it on ur desktop as Add.cpp (remember ‘.cpp‘ extension is must).

#include <iostream>

using namespace std;

int main() 
    {
          int a;
          int b;
          cout<<"Enter first number:\n";
          cin >> a;
          cout <<"Enter the second number:\n";
          cin>> b;
          cin.ignore();
          int result = a + b;
          cout<<"Result is"<<"  "<<result<<endl;
          cin.get();
          return 0;
     }
Compile it
root@tecmint:~# g++ Add.cpp
Run it
root@tecmint:~# ./a.out

Enter first number: 
...
...

Note: On compiling a c++ program the output is automatically generated to a new file “a.out” and everytime you compile a c++ program same file “a.out” gets modified. Hence it is a good advice to define a output file during compile and thus there is no risk of overwrite to output file.

Compile it this way
root@tecmint:~# g++ -o Add Add.cpp
Run it
root@tecmint:~# ./Add 

Enter first number: 
...
...

40. Command: java

Java is one of the world’s highly used programming language and is considered fast, secure, and reliable. Most of the the web based service of today runs on java.

Create a simple java program by pasting the below test to a file, named tecmint.java(remember ‘.java‘ extension is must).

class tecmint {
  public static void main(String[] arguments) {
    System.out.println("Tecmint ");
  }
}
compile it using javac
root@tecmint:~# javac tecmint.java
Run it
root@tecmint:~# java tecmint

Note: Almost every distribution comes packed with gcc compiler, major number of distros have inbuilt g++ and java compiler, while some may not have. You can apt or yum the required package.

Don’t forget to mention your valueable comment and the type of article you want to see here. I will soon be back with an interesting topic about the lesser known facts about Linux.

Part III – 20 Advanced Commands for Linux Experts

41. Command: ifconfig

ifconfig is used to configure the kernel-resident network interfaces. It is used at boot time to set up interfaces as necessary. After that, it is usually only needed when debugging or when system tuning is needed.

Check Active Network Interfaces
[avishek@tecmint ~]$ ifconfig 

eth0      Link encap:Ethernet  HWaddr 40:2C:F4:EA:CF:0E  
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0 
          inet6 addr: fe80::422c:f4ff:feea:cf0e/64 Scope:Link 
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1 
          RX packets:163843 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:124990 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:1000 
          RX bytes:154389832 (147.2 MiB)  TX bytes:65085817 (62.0 MiB) 
          Interrupt:20 Memory:f7100000-f7120000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0 
          inet6 addr: ::1/128 Scope:Host 
          UP LOOPBACK RUNNING  MTU:16436  Metric:1 
          RX packets:78 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:78 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:0 
          RX bytes:4186 (4.0 KiB)  TX bytes:4186 (4.0 KiB)
Check All Network Interfaces

Display details of All interfaces including disabled interfaces using “-a” argument.

[avishek@tecmint ~]$ ifconfig -a

eth0      Link encap:Ethernet  HWaddr 40:2C:F4:EA:CF:0E  
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0 
          inet6 addr: fe80::422c:f4ff:feea:cf0e/64 Scope:Link 
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1 
          RX packets:163843 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:124990 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:1000 
          RX bytes:154389832 (147.2 MiB)  TX bytes:65085817 (62.0 MiB) 
          Interrupt:20 Memory:f7100000-f7120000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0 
          inet6 addr: ::1/128 Scope:Host 
          UP LOOPBACK RUNNING  MTU:16436  Metric:1 
          RX packets:78 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:78 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:0 
          RX bytes:4186 (4.0 KiB)  TX bytes:4186 (4.0 KiB) 

virbr0    Link encap:Ethernet  HWaddr 0e:30:a3:3a:bf:03  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
Disable an Interface
[avishek@tecmint ~]$ ifconfig eth0 down
Enable an Interface
[avishek@tecmint ~]$ ifconfig eth0 up
Assign IP Address to an Interface

Assign “192.168.1.12″ as the IP address for the interface eth0.

[avishek@tecmint ~]$ ifconfig eth0 192.168.1.12
Change Subnet Mask of Interface eth0
[avishek@tecmint ~]$ ifconfig eth0 netmask 255.255.255.
Change Broadcast Address of Interface eth0
[avishek@tecmint ~]$ ifconfig eth0 broadcast 192.168.1.255
Assign IP Address, Netmask and Broadcast to Interface eth0
[avishek@tecmint ~]$ ifconfig eth0 192.168.1.12 netmask 255.255.255.0 broadcast 192.168.1.255

Note: If using a wireless network you need to use command “iwconfig“. For more “ifconfig” command examples and usage, read 15 Useful “ifconfig” Commands.

42. Command: netstat

netstat command displays various network related information such as network connections, routing tables, interface statistics, masquerade connections, multicast memberships etc..,

List All Network Ports
[avishek@tecmint ~]$ netstat -a

Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     STREAM     LISTENING     741379   /run/user/user1/keyring-I5cn1c/gpg
unix  2      [ ACC ]     STREAM     LISTENING     8965     /var/run/acpid.socket
unix  2      [ ACC ]     STREAM     LISTENING     18584    /tmp/.X11-unix/X0
unix  2      [ ACC ]     STREAM     LISTENING     741385   /run/user/user1/keyring-I5cn1c/ssh
unix  2      [ ACC ]     STREAM     LISTENING     741387   /run/user/user1/keyring-I5cn1c/pkcs11
unix  2      [ ACC ]     STREAM     LISTENING     20242    @/tmp/dbus-ghtTjuPN46
unix  2      [ ACC ]     STREAM     LISTENING     13332    /var/run/samba/winbindd_privileged/pipe
unix  2      [ ACC ]     STREAM     LISTENING     13331    /tmp/.winbindd/pipe
unix  2      [ ACC ]     STREAM     LISTENING     11030    /var/run/mysqld/mysqld.sock
unix  2      [ ACC ]     STREAM     LISTENING     19308    /tmp/ssh-qnZadSgJAbqd/agent.3221
unix  2      [ ACC ]     STREAM     LISTENING     436781   /tmp/HotShots
unix  2      [ ACC ]     STREAM     LISTENING     46110    /run/user/ravisaive/pulse/native
unix  2      [ ACC ]     STREAM     LISTENING     19310    /tmp/gpg-zfE9YT/S.gpg-agent
....
List All TCP Ports
[avishek@tecmint ~]$ netstat -at

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 localhost:mysql         *:*                     LISTEN     
tcp        0      0 *:5901                  *:*                     LISTEN     
tcp        0      0 *:5902                  *:*                     LISTEN     
tcp        0      0 *:x11-1                 *:*                     LISTEN     
tcp        0      0 *:x11-2                 *:*                     LISTEN     
tcp        0      0 *:5938                  *:*                     LISTEN     
tcp        0      0 localhost:5940          *:*                     LISTEN     
tcp        0      0 ravisaive-OptiPl:domain *:*                     LISTEN     
tcp        0      0 ravisaive-OptiPl:domain *:*                     LISTEN     
tcp        0      0 localhost:ipp           *:*                     LISTEN     
tcp        0      0 ravisaive-OptiPle:48270 ec2-23-21-236-70.c:http ESTABLISHED
tcp        0      0 ravisaive-OptiPle:48272 ec2-23-21-236-70.c:http TIME_WAIT  
tcp        0      0 ravisaive-OptiPle:48421 bom03s01-in-f22.1:https ESTABLISHED
tcp        0      0 ravisaive-OptiPle:48269 ec2-23-21-236-70.c:http ESTABLISHED
tcp        0      0 ravisaive-OptiPle:39084 channel-ecmp-06-f:https ESTABLISHED
...
Show Statistics for All Ports
[avishek@tecmint ~]$ netstat -s

Ip:
    4994239 total packets received
    0 forwarded
    0 incoming packets discarded
    4165741 incoming packets delivered
    3248924 requests sent out
    8 outgoing packets dropped
Icmp:
    29460 ICMP messages received
    566 input ICMP message failed.
    ICMP input histogram:
        destination unreachable: 98
        redirects: 29362
    2918 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
        destination unreachable: 2918
IcmpMsg:
        InType3: 98
        InType5: 29362
        OutType3: 2918
Tcp:
    94533 active connections openings
    23 passive connection openings
    5870 failed connection attempts
    7194 connection resets received
....

OK! For some reason if you want not to resolve host, port and user name as a output of netstat.

[avishek@tecmint ~]$ netstat -an

Fine, you may need to get the output of netstat continuously till interrupt instruction is passed (ctrl+c).

[avishek@tecmint ~]$ netstat -c

For more “netstat” command examples and usage, see the article 20 Netstat Command Examples.

43. Command: nslookup

A network utility program used to obtain information about Internet servers. As its name suggests, the utility finds name server information for domains by querying DNS.

[avishek@tecmint ~]$ nslookup tecmint.com 

Server:		192.168.1.1 
Address:	192.168.1.1#53 

Non-authoritative answer: 
Name:	tecmint.com 
Address: 50.16.67.239
Query Mail Exchanger Record
[avishek@tecmint ~]$ nslookup -query=mx tecmint.com 

Server:		192.168.1.1 
Address:	192.168.1.1#53 

Non-authoritative answer: 
tecmint.com	mail exchanger = 0 smtp.secureserver.net. 
tecmint.com	mail exchanger = 10 mailstore1.secureserver.net. 

Authoritative answers can be found from:
Query Name Server
[avishek@tecmint ~]$ nslookup -type=ns tecmint.com 

Server:		192.168.1.1 
Address:	192.168.1.1#53 

Non-authoritative answer: 
tecmint.com	nameserver = ns3404.com. 
tecmint.com	nameserver = ns3403.com. 

Authoritative answers can be found from:
Query DNS Record
[avishek@tecmint ~]$ nslookup -type=any tecmint.com 

Server:		192.168.1.1 
Address:	192.168.1.1#53 

Non-authoritative answer: 
tecmint.com	mail exchanger = 10 mailstore1.secureserver.net. 
tecmint.com	mail exchanger = 0 smtp.secureserver.net. 
tecmint.com	nameserver = ns06.domaincontrol.com. 
tecmint.com	nameserver = ns3404.com. 
tecmint.com	nameserver = ns3403.com. 
tecmint.com	nameserver = ns05.domaincontrol.com. 

Authoritative answers can be found from:
Query Start of Authority
[avishek@tecmint ~]$ nslookup -type=soa tecmint.com 

Server:		192.168.1.1 
Address:	192.168.1.1#53 

Non-authoritative answer: 
tecmint.com 
	origin = ns3403.hostgator.com 
	mail addr = dnsadmin.gator1702.hostgator.com 
	serial = 2012081102 
	refresh = 86400 
	retry = 7200 
	expire = 3600000 
	minimum = 86400 

Authoritative answers can be found from:
Query Port Number

Change the port number using which you want to connect

[avishek@tecmint ~]$ nslookup -port 56 tecmint.com

Server:		tecmint.com
Address:	50.16.76.239#53

Name:	56
Address: 14.13.253.12

Read Also : 8 Nslookup Commands

44. Command: dig

dig is a tool for querying DNS nameservers for information about host addresses, mail exchanges, nameservers, and related information. This tool can be used from any Linux (Unix) orMacintosh OS X operating system. The most typical use of dig is to simply query a single host.

[avishek@tecmint ~]$ dig tecmint.com

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com 
;; global options: +cmd 
;; Got answer: 
;; ->>HEADER<
Turn Off Comment Lines
[avishek@tecmint ~]$ dig tecmint.com +nocomments 

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com +nocomments 
;; global options: +cmd 
;tecmint.com.			IN	A 
tecmint.com.		14400	IN	A	40.216.66.239 
;; Query time: 418 msec 
;; SERVER: 192.168.1.1#53(192.168.1.1) 
;; WHEN: Sat Jun 29 13:53:22 2013 
;; MSG SIZE  rcvd: 45
Turn Off Authority Section
[avishek@tecmint ~]$ dig tecmint.com +noauthority 

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com +noauthority 
;; global options: +cmd 
;; Got answer: 
;; ->>HEADER<
Turn Off Additional Section
[avishek@tecmint ~]$ dig  tecmint.com +noadditional 

; <<>> DiG 9.9.2-P1 <<>> tecmint.com +noadditional
;; global options: +cmd
;; Got answer:
;; ->>HEADER<
Turn Off Stats Section
[avishek@tecmint ~]$ dig tecmint.com +nostats 

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com +nostats 
;; global options: +cmd 
;; Got answer: 
;; ->>HEADER<
Turn Off Answer Section
[avishek@tecmint ~]$ dig tecmint.com +noanswer 

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com +noanswer 
;; global options: +cmd 
;; Got answer: 
;; ->>HEADER<
Disable All Section at Once
[avishek@tecmint ~]$ dig tecmint.com +noall 

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>> tecmint.com +noall 
;; global options: +cmd

Read Also : 10 Linux Dig Command Examples

45. Command: uptime

You have just connected to your Linux Server Machine and founds Something unusual or malicious, what you will do? Guessing…. NO, definitely not you could run uptime to verify what happened actually when the server was unattended.

[avishek@tecmint ~]$ uptime

14:37:10 up  4:21,  2 users,  load average: 0.00, 0.00, 0.04

46. Command: wall

one of the most important command for administrator, wall sends a message to everybody logged in with their mesg permission set to “yes“. The message can be given as an argument towall, or it can be sent to wall’s standard input.

[avishek@tecmint ~]$ wall "we will be going down for maintenance for one hour sharply at 03:30 pm"

Broadcast message from root@localhost.localdomain (pts/0) (Sat Jun 29 14:44:02 2013): 

we will be going down for maintenance for one hour sharply at 03:30 pm

47. command: mesg

Lets you control if people can use the “write” command, to send text to you over the screen.

mesg [n|y]
n - prevents the message from others popping up on the screen.
y – Allows messages to appear on your screen.

48. Command: write

Let you send text directly to the screen of another Linux machine if ‘mesg’ is ‘y’.

[avishek@tecmint ~]$ write ravisaive

49. Command: talk

An enhancement to write command, talk command lets you talk to the logged in users.

[avishek@tecmint ~]$ talk ravisaive

Note: If talk command is not installed, you can always apt or yum the required packages.

[avishek@tecmint ~]$ yum install talk
OR
[avishek@tecmint ~]$ apt-get install talk

50. Command: w

what command ‘w’ seems you funny? But actually it is not. t’s a command, even if it’s just one letter long! The command “w” is a combination of uptime and who commands given one immediately after the other, in that order.

[avishek@tecmint ~]$ w

15:05:42 up  4:49,  3 users,  load average: 0.02, 0.01, 0.00 
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT 
server   tty7     :0               14:06    4:43m  1:42   0.08s pam: gdm-passwo 
server   pts/0    :0.0             14:18    0.00s  0.23s  1.65s gnome-terminal 
server   pts/1    :0.0             14:47    4:43   0.01s  0.01s bash

51. Command: rename

As the name suggests, this command rename files. rename will rename the specified files by replacing the first occurrence from the file name.

Give the file names a1, a2, a3, a4.....1213

Just type the command.

 rename a1 a0 a?
 rename a1 a0 a??

52. Command: top

Displays the processes of CPU. This command refresh automatically, by default and continues to show CPU processes unless interrupt-instruction is given.

[avishek@tecmint ~]$ top

top - 14:06:45 up 10 days, 20:57,  2 users,  load average: 0.10, 0.16, 0.21
Tasks: 240 total,   1 running, 235 sleeping,   0 stopped,   4 zombie
%Cpu(s):  2.0 us,  0.5 sy,  0.0 ni, 97.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem:   2028240 total,  1777848 used,   250392 free,    81804 buffers
KiB Swap:  3905532 total,   156748 used,  3748784 free,   381456 cached

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+ COMMAND                                                                                                            
23768 ravisaiv  20   0 1428m 571m  41m S   2.3 28.9  14:27.52 firefox                                                                                                            
24182 ravisaiv  20   0  511m 132m  25m S   1.7  6.7   2:45.94 plugin-containe                                                                                                    
26929 ravisaiv  20   0  5344 1432  972 R   0.7  0.1   0:00.07 top                                                                                                                
24875 ravisaiv  20   0  263m  14m  10m S   0.3  0.7   0:02.76 lxterminal                                                                                                         
    1 root      20   0  3896 1928 1228 S   0.0  0.1   0:01.62 init                                                                                                               
    2 root      20   0     0    0    0 S   0.0  0.0   0:00.06 kthreadd                                                                                                           
    3 root      20   0     0    0    0 S   0.0  0.0   0:17.28 ksoftirqd/0                                                                                                        
    5 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 kworker/0:0H                                                                                                       
    7 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 kworker/u:0H                                                                                                       
    8 root      rt   0     0    0    0 S   0.0  0.0   0:00.12 migration/0                                                                                                        
    9 root      20   0     0    0    0 S   0.0  0.0   0:00.00 rcu_bh                                                                                                             
   10 root      20   0     0    0    0 S   0.0  0.0   0:26.94 rcu_sched                                                                                                          
   11 root      rt   0     0    0    0 S   0.0  0.0   0:01.95 watchdog/0                                                                                                         
   12 root      rt   0     0    0    0 S   0.0  0.0   0:02.00 watchdog/1                                                                                                         
   13 root      20   0     0    0    0 S   0.0  0.0   0:17.80 ksoftirqd/1                                                                                                        
   14 root      rt   0     0    0    0 S   0.0  0.0   0:00.12 migration/1                                                                                                        
   16 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 kworker/1:0H                                                                                                       
   17 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 cpuset                                                                                                             
   18 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 khelper                                                                                                            
   19 root      20   0     0    0    0 S   0.0  0.0   0:00.00 kdevtmpfs                                                                                                          
   20 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 netns                                                                                                              
   21 root      20   0     0    0    0 S   0.0  0.0   0:00.04 bdi-default                                                                                                        
   22 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 kintegrityd                                                                                                        
   23 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 kblockd                                                                                                            
   24 root       0 -20     0    0    0 S   0.0  0.0   0:00.00 ata_sff

Read Also : 12 TOP Command Examples

53. Command: mkfs.ext4

This command create a new ext4 file system on the specified device, if wrong device is followed after this command, the whole block will be wiped and formatted, hence it is suggested not to run this command unless and until you understand what you are doing.

Mkfs.ext4 /dev/sda1 (sda1 block will be formatted)
mkfs.ext4 /dev/sdb1 (sdb1 block will be formatted)

Read MoreWhat is Ext4 and How to Create and Convert

54. Command: vi/emacs/nano

vi (visual), emacsnano are some of the most commonly used editors in Linux. They are used oftenly to edit text, configuration,… files. A quick guide to work around vi and nano is, emacs is a.

vi-editor
[avishek@tecmint ~]$ touch a.txt (creates a text file a.txt) 
[avishek@tecmint ~]$ vi a.txt (open a.txt with vi editor)

[press ‘i’ to enter insert mode, or you won’t be able to type-in anything]

echo "Hello"  (your text here for the file)
  1. alt+x (exit insert mode, remember to keep some space between the last letter.
  2. ctrl+x command or your last word will be deleted).
  3. :wq! (saves the file, with the current text, remember ‘!’ is to override).
nano editor
[avishek@tecmint ~]$ nano a.txt (open a.txt file to be edited with nano)
edit, with the content, required

ctrl +x (to close the editor). It will show output as:

Save modified buffer (ANSWERING "No" WILL DESTROY CHANGES) ?                    
 Y Yes 
 N No           ^C Cancel

Click ‘y’ to yes and enter file name, and you are done.

55. Command: rsync

Rsync copies files and has a -P switch for a progress bar. So if you have rsync installed, you could use a simple alias.

alias cp='rsync -aP'

Now try to copy a large file in terminal and see the output with remaining items, similar to a progress bar.

Moreover, Keeping and Maintaining backup is one of the most important and boring work a system administrator, needs to perform. Rsync is a very nice tool (there exists, several other) to create and maintain backup, in terminal.

[avishek@tecmint ~]$ rsync -zvr IMG_5267\ copy\=33\ copy\=ok.jpg ~/Desktop/ 

sending incremental file list 
IMG_5267 copy=33 copy=ok.jpg 

sent 2883830 bytes  received 31 bytes  5767722.00 bytes/sec 
total size is 2882771  speedup is 1.00

Note-z for compression, -v for verbose and -r for recursive.

56. Command: free

Keeping track of memory and resources is as much important, as any other task performed by an administrator, and ‘free‘ command comes to rescue here.

Current Usage Status of Memory
[avishek@tecmint ~]$ free

             total       used       free     shared    buffers     cached
Mem:       2028240    1788272     239968          0      69468     363716
-/+ buffers/cache:    1355088     673152
Swap:      3905532     157076    3748456
Tuned Output in KB, or MB, or GB
[avishek@tecmint ~]$ free -b

             total       used       free     shared    buffers     cached
Mem:    2076917760 1838272512  238645248          0   71348224  372670464
-/+ buffers/cache: 1394253824  682663936
Swap:   3999264768  160845824 3838418944
[avishek@tecmint ~]$ free -k

             total       used       free     shared    buffers     cached
Mem:       2028240    1801484     226756          0      69948     363704
-/+ buffers/cache:    1367832     660408
Swap:      3905532     157076    3748456
[avishek@tecmint ~]$ free -m

             total       used       free     shared    buffers     cached
Mem:          1980       1762        218          0         68        355
-/+ buffers/cache:       1338        641
Swap:         3813        153       3660
[avishek@tecmint ~]$ free -g

             total       used       free     shared    buffers     cached
Mem:             1          1          0          0          0          0
-/+ buffers/cache:          1          0
Swap:            3          0          3
Check Current Usage in Human Readable Format
[avishek@tecmint ~]$ free -h

             total       used       free     shared    buffers     cached
Mem:          1.9G       1.7G       208M         0B        68M       355M
-/+ buffers/cache:       1.3G       632M
Swap:         3.7G       153M       3.6G
Check Status Contineously After Regular Interval
[avishek@tecmint ~]$ free -s 3

             total       used       free     shared    buffers     cached
Mem:       2028240    1824096     204144          0      70708     364180
-/+ buffers/cache:    1389208     639032
Swap:      3905532     157076    3748456

             total       used       free     shared    buffers     cached
Mem:       2028240    1824192     204048          0      70716     364212
-/+ buffers/cache:    1389264     638976
Swap:      3905532     157076    3748456

Read Also : 10 Examples of Free Command

57. Command: mysqldump

Ok till now you would have understood what this command actually stands for, from the name of this command.mysqldump commands dumps (backups) all or a particular database data into a given a file.For example,

[avishek@tecmint ~]$ mysqldump -u root -p --all-databases > /home/server/Desktop/backupfile.sql

Notemysqldump requires mysql to be running and correct password for authorisation. We have covered some useful “mysqldump” commands at Database Backup with mysqldump Command

58. Command: mkpasswd

Make a hard-to-guess, random password of the length as specified.

[avishek@tecmint ~]$ mkpasswd -l 10

zI4+Ybqfx9
[avishek@tecmint ~]$ mkpasswd -l 20 

w0Pr7aqKk&hmbmqdrlmk

Note-l 10 generates a random password of 10 characters while -l 20 generates a password of character 20, it could be set to anything to get desired result. This command is very useful and implemented in scripting language oftenly to generate random passwords. You might need toyum or apt the ‘expect’ package to use this command.

[avishek@tecmint ~]$ yum install expect 
OR
[avishek@tecmint ~]$ apt-get install expect

59. Command: paste

Merge two or more text files on lines using. Example. If the content of file1 was:

1 
2 
3 

and file2 was: 

a 
b 
c 
d 
the resulting file3 would be: 

1    a 
2    b 
3    c 
     d

60.Command: lsof

lsof stands for “list open files” and displays all the files that your system has currently opened. It’s very useful to figure out which processes uses a certain file, or to display all the files for a single process. Some useful 10 lsof Command examples, you might be interested in reading.

[avishek@tecmint ~]$ lsof COMMAND     PID   TID            USER   FD      TYPE     DEVICE SIZE/OFF       NODE NAME
init          1                  root  cwd       DIR        8,1     4096          2 /
init          1                  root  rtd       DIR        8,1     4096          2 /
init          1                  root  txt       REG        8,1   227432     395571 /sbin/init
init          1                  root  mem       REG        8,1    47080     263023 /lib/i386-linux-gnu/libnss_files-2.17.so
init          1                  root  mem       REG        8,1    42672     270178 /lib/i386-linux-gnu/libnss_nis-2.17.so
init          1                  root  mem       REG        8,1    87940     270187 /lib/i386-linux-gnu/libnsl-2.17.so
init          1                  root  mem       REG        8,1    30560     263021 /lib/i386-linux-gnu/libnss_compat-2.17.so
init          1                  root  mem       REG        8,1   124637     270176 /lib/i386-linux-gnu/libpthread-2.17.so
init          1                  root  mem       REG        8,1  1770984     266166 /lib/i386-linux-gnu/libc-2.17.so
init          1                  root  mem       REG        8,1    30696     262824 /lib/i386-linux-gnu/librt-2.17.so
init          1                  root  mem       REG        8,1    34392     262867 /lib/i386-linux-gnu/libjson.so.0.1.0
init          1                  root  mem       REG        8,1   296792     262889 /lib/i386-linux-gnu/libdbus-1.so.3.7.2
init          1                  root  mem       REG        8,1    34168     262840 /lib/i386-linux-gnu/libnih-dbus.so.1.0.0
init          1                  root  mem       REG        8,1    95616     262848 /lib/i386-linux-gnu/libnih.so.1.0.0
init          1                  root  mem       REG        8,1   134376     270186 /lib/i386-linux-gnu/ld-2.17.so
init          1                  root    0u      CHR        1,3      0t0       1035 /dev/null
init          1                  root    1u      CHR        1,3      0t0       1035 /dev/null
init          1                  root    2u      CHR        1,3      0t0       1035 /dev/null
init          1                  root    3r     FIFO        0,8      0t0       1714 pipe
init          1                  root    4w     FIFO        0,8      0t0       1714 pipe
init          1                  root    5r     0000        0,9        0       6245 anon_inode
init          1                  root    6r     0000        0,9        0       6245 anon_inode
init          1                  root    7u     unix 0xf5e91f80      0t0       8192 @/com/ubuntu/upstart
init          1                  root    8w      REG        8,1     3916        394 /var/log/upstart/teamviewerd.log.1 (deleted)

This is not the end, a System Administrator does a lot of stuff, to provide you such a nice interface, upon which you work. System Administration is actually an art of learning and implementing in a very much perfect way. We will try to get you with all other necessary stuff which a linux professional must learn, linux in its basic actually itself, is a process of learning and learning. Your good words are always sought, which encourages us to put in more effort to give you a knowledgeable article. “Like and share Us, to help Us Spread”.

 
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Posted by on August 21, 2013 in Ubuntu, Unix & Linux

 

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Keyboard Shortcuts (Windows)

The General Shortcuts

We’ll kickoff the list with some really general shortcuts that you often used.

  • CTRL+C (Copy)
  • CTRL+X (Cut)
  • CTRL+V (Paste)
  • CTRL+Z (Undo)
  • Delete (Delete)
  • Shift+Delete (Delete the selected item permanently without placing the item in the Recycle Bin)
  • CTRL while dragging an item (Copy the selected item)
  • CTRL+Shift while dragging an item (Create a shortcut to the selected item)
  • F2 key (Rename the selected item)
  • CTRL+RIGHT ARROW (Move the insertion point to the beginning of the next word)
  • CTRL+LEFT ARROW (Move the insertion point to the beginning of the previous word)
  • CTRL+DOWN ARROW (Move the insertion point to the beginning of the next paragraph)
  • CTRL+UP ARROW (Move the insertion point to the beginning of the previous paragraph)
  • CTRL+Shift with any of the arrow keys (Highlight a block of text)
  • Shift with any of the arrow keys (Select more than one item in a window or on the desktop, or select text in a document)
  • CTRL+A (Select all)
  • F3 key (Search for a file or a folder)
  • Alt+Enter (View the properties for the selected item)
  • Alt+F4 (Close the active item, or quit the active program)
  • Alt+Enter (Display the properties of the selected object)
  • Alt+Spacebar (Open the shortcut menu for the active window)
  • CTRL+F4 (Close the active document in programs that enable you to have multiple documents open simultaneously)
  • Alt+Tab (Switch between the open items)
  • Alt+ESC (Cycle through items in the order that they had been opened)
  • F6 key (Cycle through the screen elements in a window or on the desktop)
  • F4 key (Display the Address bar list in My Computer or Windows Explorer)
  • Shift+F10 (Display the shortcut menu for the selected item)
  • Alt+Spacebar (Display the System menu for the active window)
  • CTRL+ESC (Display the Start menu)
  • Alt+Underlined letter in a menu name (Display the corresponding menu)
  • Underlined letter in a command name on an open menu (Perform the corresponding command)
  • F10 key (Activate the menu bar in the active program)
  • RIGHT ARROW (Open the next menu to the right, or open a submenu)
  • LEFT ARROW (Open the next menu to the left, or close a submenu)
  • F5 key (Update the active window)
  • Backspace (View the folder one level up in My Computer or Windows Explorer)
  • ESC (Cancel the current task)
  • Shift when you insert a CD-ROM into the CD-ROM drive (Prevent the CD-ROM from automatically playing)

 

Dialog Box Keyboard Shortcuts

  • CTRL+Tab (Move forward through the tabs)
  • CTRL+Shift+Tab (Move backward through the tabs)
  • Tab (Move forward through the options)
  • Shift+Tab (Move backward through the options)
  • Alt+Underlined letter (Perform the corresponding command or select the corresponding option)
  • Enter (Perform the command for the active option or button)
  • Spacebar (Select or clear the check box if the active option is a check box)
  • Arrow keys (Select a button if the active option is a group of option buttons)
  • F1 key (Display Help)
  • F4 key (Display the items in the active list)
  • Backspace (Open a folder one level up if a folder is selected in the Save As or Open dialog box)

Microsoft Natural Keyboard Shortcuts

  • Win (Display or hide the Start menu)
  • Win+BREAK (Display the System Properties dialog box)
  • Win+D (Display the desktop)
  • Win+M (Minimize all of the windows)
  • Win+Shift+M (Restore the minimized windows)
  • Win+E (Open My Computer)
  • Win+F (Search for a file or a folder)
  • CTRL+Win+F (Search for computers)
  • Win+F1 (Display Windows Help)
  • Win+ L (Lock the keyboard)
  • Win+R (Open the Run dialog box)
  • Win+U (Open Utility Manager)

Accessibility Keyboard Shortcuts

  • Right Shift for eight seconds (Switch FilterKeys either on or off)
  • Left Alt+left Shift+PRINT SCREEN (Switch High Contrast either on or off)
  • Left Alt+left Shift+NUM LOCK (Switch the MouseKeys either on or off)
  • Shift five times (Switch the StickyKeys either on or off)
  • NUM LOCK for five seconds (Switch the ToggleKeys either on or off)
  • Win +U (Open Utility Manager)

Windows Explorer Keyboard Shortcuts

  • END (Display the bottom of the active window)
  • HOME (Display the top of the active window)
  • NUM LOCK+* (Display all of the subfolders that are under the selected folder)
  • NUM LOCK++ (Display the contents of the selected folder)
  • NUM LOCK+- (Collapse the selected folder)
  • LEFT ARROW (Collapse the current selection if it is expanded, or select the parent folder)
  • RIGHT ARROW (Display the current selection if it is collapsed, or select the first subfolder)

Shortcut Keys For Character Map

  • After you double-click a character on the grid of characters, you can move through the grid by using the keyboard shortcuts:
  • RIGHT ARROW (Move to the right or to the beginning of the next line)
  • LEFT ARROW (Move to the left or to the end of the previous line)
  • UP ARROW (Move up one row)
  • DOWN ARROW (Move down one row)
  • PAGE UP (Move up one screen at a time)
  • PAGE DOWN (Move down one screen at a time)
  • HOME (Move to the beginning of the line)
  • END (Move to the end of the line)
  • CTRL+HOME (Move to the first character)
  • CTRL+END (Move to the last character)
  • Spacebar (Switch between Enlarged and Nor mal mode when a character is selected)

Microsoft Management Console (MMC) Main Window Keyboard Shortcuts

  • CTRL+O (Open a saved console)
  • CTRL+N (Open a new console)
  • CTRL+S (Save the open console)
  • CTRL+M (Add or remove a console item)
  • CTRL+W (Close window/tab)
  • F5 key (Update the content of all console windows)
  • Alt+Spacebar (Display the MMC window menu)
  • Alt+F4 (Close the console)
  • Alt+A (Display the Action menu)
  • Alt+V (Display the View menu)
  • Alt+F (Display the File menu)
  • Alt+O (Display the Favorites menu)

MMC Console Window Keyboard Shortcuts

  • CTRL+P (Print the current page or active pane)
  • Alt+- (Display the window menu for the active console window)
  • Shift+F10 (Display the Action shortcut menu for the selected item)
  • F1 key (Open the Help topic, if any, for the selected item)
  • F5 key (Update the content of all console windows)
  • CTRL+F10 (Maximize the active console window)
  • CTRL+F5 (Restore the active console window)
  • Alt+Enter (Display the Properties dialog box, if any, for the selected item)
  • F2 key (Rename the selected item)
  • CTRL+F4 (Close the active console window. When a console has only one console window, this shortcut closes the console)

Remote Desktop Connection Navigation

 

  • CTRL+Alt+END (Open the m*cro$oft Windows NT Security dialog box)
  • Alt+PAGE UP (Switch between programs from left to right)
  • Alt+PAGE DOWN (Switch between programs from right to left)
  • Alt+INSERT (Cycle through the programs in most recently used order)
  • Alt+HOME (Display the Start menu)
  • CTRL+Alt+BREAK (Switch the client computer between a window and a full screen)
  • Alt+Delete (Display the Windows menu)
  • CTRL+Alt+- (Place a snapshot of the active window in the client on the Terminal server clipboard and provide the same functionality as pressing PRINT SCREEN on a local computer.)
  • CTRL+Alt++ (Place a snapshot of the entire client window area on the Terminal server clipboard and provide the same functionality as pressing Alt+PRINT SCREEN on a local computer.)

Internet Explorer Navigation

  • CTRL+B (Open the Organize Favorites dialog box)
  • CTRL+E (Open the Search bar)
  • CTRL+F (Start the Find utility)
  • CTRL+H (Open the History bar)
  • CTRL+I (Open the Favorites bar)
  • CTRL+L (Open the Open dialog box)
  • CTRL+N (Start another instance of the browser with the same Web address)
  • CTRL+O (Open the Open dialog box, the same as CTRL+L)
  • CTRL+P (Open the Print dialog box)
  • CTRL+R (Update the current Web page)
  • CTRL+W (Close the current window)
 
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Posted by on July 30, 2013 in WINDOWS

 

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