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Common Linux Configuration Files

Rai — Mon, 01 Feb 2010 06:05:18 +0000

Every user who switches from Windows to Linux has the fear of editing configuration files using the command line interface (CLI). If you are one of those people, then I am here to guide you through the most common configuration files found in a Linux system. Please note that to be able to edit these files, you need to have knowledge in file editors such as vim or pico.

/etc/profile
System wide environment variables for all users.

/etc/fstab
List of devices and their associated mount points. Edit this file to add cdroms, DOS partitions and floppy drives at startup.

/etc/motd
Message of the day broadcast to all users at login.

/etc/rc.d/rc.local
Bash script that is executed at the end of login process. Similar to autoexec.bat in DOS.

/etc/hostname
Contains full hostname including domain.

/etc/cron.*
There are 4 directories that automatically execute all scripts within the directory at intervals of hour, day, week or month.

/etc/hosts
A list of all know host names and IP addresses on the machine.

/etc/httpd/conf
Parameters for the Apache web server

/etc/inittab
Specifies the run level that the machine should boot into.

/etc/resolv.conf
Defines IP addresses of DNS servers.

Linux Shortcuts Every Newbie Should Know

Rai — Sun, 31 Jan 2010 05:25:29 +0000

Linux Shortcuts Every Newbie Should Know

One thing that Linux is not so popular of is that it has quite a few keyboard shortcuts that every Linux user should know. Here are a few examples of Linux shortcuts that will help anyone who uses Linux.

Switch to the first text terminal. Under Linux you can have several (6 in standard setup) terminals opened at the same time.

(n=1..6)
Switch to the nth text terminal.

tty
Print the name of the terminal in which you are typing this command.

Switch to the first GUI terminal (if X-windows is running on this terminal).

(n=7..12)
Switch to the nth GUI terminal (if a GUI terminal is running on screen n-1). By default, nothing is running on terminals 8 to 12, but you can run another server there.

(In a text terminal) Autocomplete the command if there is only one option, or else show all the available options.

Scroll and edit the command history. Press to execute.

Scroll terminal output up. Work also at the login prompt, so you can scroll through your bootup messages.

Scroll terminal output down.

<+>
(in X-windows) Change to the next X-server resolution (if you set up the X-server to more than one resolution). For multiple resolutions on my standard SVGA card/monitor, I have the following line in the file /etc/X11/XF86Config (the first resolution starts on default, the largest determines the size of the “virtual screen”):
Modes “1024×768″ “800×600″ “640×480″ “512×384″ “480×300″ “400×300″ “1152×864″

<->
(in X-windows) Change to the previous X-server resolution.

(in X-windows) Kill the current X-windows server. Use if the X-windows server crushes and cannot be exited normally.

Shut down the system and reboot. This is the normal shutdown command for a user at the text-mode console. Don’t just press the “reset” button for shutdown!

c
Kill the current process (mostly in the text mode for small applications).

d
Log out from the current terminal. See also the next command.

d
Send [End-of-File] to the current process. Don’t press it twice else you also log out (see the previous command).

How to Use watch Command

Rai — Fri, 08 Jan 2010 11:13:05 +0000

If you need to execute a certain command repeatedly, you may use the watch command to do the repeating for you.

In this example, the command ps will be run every 2 seconds to monitor how fast the new processes spawn:

$ watch -n2 "ps aux|grep http"

The watch command will run ps every two seconds and it will display the output in stdout. You may increase or decrease the interval as necessary. This is useful if you want to monitor a process at certain time intervals. Personally, I use this to check for processes that spawns children way too fast.

Send Email in One Line

Rai — Thu, 07 Jan 2010 10:57:15 +0000

I use this nifty one liner to test if a Linux machine can send emails.

$ echo "This is the body of the email" | mail -s "This is the subject" rai@email.com

You need to install the package mailx (Red Hat or Fedora) to have the mail command.

How to Use the alias Command

Rai — Wed, 06 Jan 2010 10:47:39 +0000

Let us say you execute the command ‘ls –alh’ every time you need a long listing of files and directories. Now you want a shortcut to do this. Fortunately, you can do so by using the command alias.

The alias command is useful for creating shortcuts for long commands or for correcting typing mistakes.

To create a shortcut for ls, you can do this:

$ alias ls=”ls -alh”

Now, everytime you execute ls command, it will be run as if you are executing the whole ls –alh command. Be reminded that this will replace the existing ls command. You may use a different name for the new shortcut like so:

$ alias ll=”ls -alh”

However, once you exit the current terminal, the alias will not be saved. To make the alias permanent, you may edit the .bashrc file in user’s home directory:

$ vi ~rai/.bashrc

Then insert the alias command after the line that says #system wide functions and aliases. Save and exit.

That should do it!

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