Getting Started with Linux

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Let's start from very begining and the first step of Linux is to boot the system to make it live which allows users to interact with it. So let's start with System Bootup.

System Bootup

If you have a computer which has the Linux operating system installed in it, then you simply need to turn on the power of the system to make it live.

As soon as you turn on the Linux system (You can say also Linux Machine), it starts booting up and finally it prompts you to log into the system, which is an activity to log into the system and use it for your day-to-day activities.

A typical login screen for Ubuntu Linux System looks like as follows:

Login Linux

When you first connect to a Linux/Unix system, you usually see a Login prompt such as the following −

login:

To log in

• Have your userid (user identification) and password ready. Contact your system administrator if you don't have these yet.

• Type your userid at the login prompt, then press ENTER. Your userid is case-sensitive, so be sure you type it exactly as your system administrator has instructed.

• Type your password at the password prompt, then press ENTER. Your password is also case-sensitive.

• If you provide the correct userid and password, then you will be allowed to enter into the system. Read the information and messages that comes up on the screen, which is as follows.

login : amrood
amrood's password:
Last login: Sun Jun 14 09:32:32 2009 from 62.61.164.73
$

Once you are successfully logged into the Linux system, you will be provided with a command prompt (sometime called the $ prompt ) where you type all Linux commands. For example, to check calendar, you need to type the cal command as follows −

$ cal
     June 2009
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

$

Following section will discuss few important Linux functions alongwith associated commands.

Change Password

All Linux systems require passwords to help ensure that your files and data remain your own and that the system itself is secure from hackers and crackers. It is advised to change your password frequently to save it from hackers or any other misuse. Following are the steps to change your password −

Step 1 − To start, type passwd command at the command prompt as shown below.

Step 2 − Enter your old password, the one you're currently using.

Step 3 − Type in your new password. Always keep your password complex enough so that nobody can guess it. But make sure, you remember it.

Step 4 − You must verify the password by typing it again.

$ passwd
Changing password for amrood
(current) Linux password:******
New Linux password:*******
Retype new Linux password:*******
passwd: all authentication tokens updated  successfully

$

We have added asterisk (*) here just to show the location where you need to enter the current and new passwords otherwise at your system. It does not show you any character when you type.

Most of the Linux variants will show the steps sequence more or less same, but given instructions should be good enough for you to change your password.

Listing Directories and Files

All the data in Liux is organized into files and all the files are organized into different directories. These directories are organized into a tree-like structure called the filesystem.

You can use the Linux ls command to list out all the files or directories available in a directory. Following is the example of using ls command with -l option.

$ ls -l
total 19621
drwxrwxr-x  2 amrood amrood      4096 Dec 25 09:59 uml
-rw-rw-r--  1 amrood amrood      5341 Dec 25 08:38 uml.jpg
drwxr-xr-x  2 amrood amrood      4096 Feb 15  2006 univ
drwxr-xr-x  2 root   root        4096 Dec  9  2007 urlspedia
-rw-r--r--  1 root   root      276480 Dec  9  2007 urlspedia.tar
drwxr-xr-x  8 root   root        4096 Nov 25  2007 usr
-rwxr-xr-x  1 root   root        3192 Nov 25  2007 webthumb.php
-rw-rw-r--  1 amrood amrood     20480 Nov 25  2007 webthumb.tar
-rw-rw-r--  1 amrood amrood      5654 Aug  9  2007 yourfile.mid
-rw-rw-r--  1 amrood amrood    166255 Aug  9  2007 yourfile.swf

$

Here entries starting with d..... represent directories. For example, uml, univ and urlspedia are directories and rest of the entries are files.

Changing Directories

While working with different files and directories you will need to go in different directories. You can go inside a directory using the cd command as follows:

$ cd uml

$

Above command will take you inside uml directory, where you can list available directories and files. Once you are done with your work in a directory, you can go back to parent directory using cd .. as follows:

$ cd ..

$

Linux uses a single dot . to represent current directory and double dots .. to represent a parent directory.

Who Are You?

While you're logged into the system, you might be willing to know : Who am I? or you would like to know whose login you are using at present?

The easiest way to find out "who you are" is to enter the whoami command as follows −

$ whoami
 amrood

$

Try it on your system. This command lists the account name associated with the current login. You can try who am i command as well to get information about yourself.

$ who am i
root     pts/2        2024-04-24 19:22 (49.205.240.120)

$

Who is Logged in?

Sometime you might be interested to know who is logged in to the computer at the same time.

There are three commands available to get you this information, based on how much you wish to know about the other users: users, who, and w.

$ users
 amrood bablu qadir

$ who
amrood pts1 Oct 8 14:10 (limbo)
bablu  pts2 Oct 4 09:08 (calliope)
qadir  pts3 Oct 8 12:09 (dent)

$

Try the w command on your system to check the output. This lists down information associated with the users logged in the system.

$ w
 19:37:51 up 91 days, 13 min,  2 users,  load average: 1.43, 1.77, 1.86
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
bablu    pts/1    49.205.240.120   19:03    7.00s  6.82s  6.79s vi unix-getting-started.htm
amrood   pts/2    49.205.240.120   19:22    0.00s  0.04s  0.01s w

$

Checking Disk Usage

Many a times you will be interested in knowing the disk usage of your computer to make sure you have enough storage available on the system. There are various commands to check the available disk, but the most frequently used is df -h and it provides information like this:

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs            13G   16M   13G   1% /run
/dev/nvme0n1p3  1.8T  260G  1.4T  16% /
tmpfs            63G     0   63G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/nvme0n1p2  975M  255M  669M  28% /boot
tmpfs            13G     0   13G   0% /run/user/0

$

Logging Out

When you finish your session, you need to log out of the system. This is to ensure that nobody else accesses your files.

To log out

• Just type the logout command at the command prompt, and the system will clean up everything and break the connection.

System Shutdown

The most consistent way to shut down a Linux system properly via the command line is to use one of the following commands −

You typically need to be the super user or root (the most privileged account on a Linux system) to shut down the system. However, on some standalone or personally-owned Linux boxes, an administrative user and sometimes regular users can do so.