HowtoForge - Linux Howtos and Tutorials - Shell

Simple Patch Tools

Fri, 30 Jul 2010 18:07:51 +0200

Simple Patch Tools

Creating: When all you want to do is build a patch file that contains only the changes you've made today. Installing: I typically want to take a backup of the files that are going to be overwritten so that I can quickly undo the patch if necessary.

The Bash Script To Configure The Firewall Using IPTABLES

Thu, 26 Jun 2008 13:58:49 +0200

About the Script:

This script is about to build a firewall in Linux OS by using iptables, the user only needs to follow and answer the simple and easy steps and the script will generate the user specified iptables rule in its original form.

I HAVE TESTED THE SCRIPT ON PCLINUXOS, FEDORA-9, DREAM_LINUX, UBUNTU-8.

This is my iptables Version 1.0 (USMAN AKRAM - Lucky)

Useful Commands For The Linux Command Line

Fri, 09 Mar 2007 17:49:32 +0100

Useful Commands For The Linux Command Line

This short guide shows some important commands for your daily work on the Linux command line.

How can I observe a logfile continuously?

Mon, 07 Aug 2006 18:44:31 +0200

With the command:

tail -f /path/to/logfile

you will see all lines added to the logfile. To stop this, press [CTRL] + c

How to save a command in the shell history without executing it

Mon, 07 Aug 2006 18:42:39 +0200

Enter the command line and hit the keys:

[CTRL] + [#]

This will put a # in front of the command and execute it. The shell will take it as comment.

How can I clear the shell window?

Mon, 07 Aug 2006 18:40:41 +0200

Use the commad:

clear

or the keyboard shortcut:

[CTRL] + [L]

Creating image borders with ImageMagick convert

Mon, 07 Aug 2006 18:37:29 +0200

The command is:

convert -border 2x2 old.jpg new.jpg

This creates a new image (new.jpg) with a 2 pixel border from the image old.jpg.

To set the bordercolor to red, use this command:

convert -border 2x2 -bordercolor "#FF0000" old.jpg new.jpg

Get a list of the installed services

Mon, 07 Aug 2006 18:32:36 +0200

To get a list of the installed services on the shell, you may use this command (on Fedora, RedHat, CentOS, SuSE, and Mandriva):

chkconfig --list

Show all processes for a specific user

Mon, 07 Aug 2006 18:31:41 +0200

To view only the processes owned by a specific user, use the following command:

top -U [USERNAME]

and replace [USERNAME] with the name of the user.

Making snapshots of the process table shown by the TOP command

Mon, 07 Aug 2006 18:29:15 +0200

To make a snapshot of the current process table, use the following command:

top -n 1 -b > /tmp/processtable.txt

You can now view the textfile with any text editor, e.g. pico or vi.

How do I search for a term in a file?

Mon, 07 Aug 2006 18:27:39 +0200

With the grep command.

If you want to find out if the term user is in /etc/httpd/conf/httpd.conf, you would run

grep -i user /etc/httpd/conf/httpd.conf

(-i makes the search case-insensitive).

Normally grep does not tell you the line number where it finds the term. If you want to find out the line number, run

grep -n -i user /etc/httpd/conf/httpd.conf

How do I find out who is logged in on my system?

Mon, 07 Aug 2006 18:23:58 +0200

You can find out about logged in users either by running

who

(Sample output:

server:~# who
root     pts/0        Nov 12 11:28 (192.168.0.202)

)

which gives more detailed output:

server:~# w
 11:29:49 up  2:19,  1 user,  load average: 0.02, 0.01, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    192.168.0.202    11:28    0.00s  0.08s  0.01s w

How do I edit files on the command line?

Mon, 07 Aug 2006 18:15:40 +0200

To edit files on the command line, you can use an editor such as vi. To open the file, run

vi /path/to/file

Now you see the contents of the file (if there is any. Please note that the file is created if it does not exist yet.).

The most important commands in vi are these:

Press i to enter the Insert mode. Now you can type in your text.

To leave the Insert mode press ESC.