Linux is Everywhere!
(I won’t bother you too much with this introduction because I know how excited I was when I started for the first time to learn Linux. You can find here a small Linux Introduction.)
Linux is a very flexible operating system and as you already may know it can be found in everything from automobiles to rockets, phones, servers, personal computers, watches, TVs, IoE/IoT devices and the list continues…
I hope that you will find this tutorial very interesting and you will enjoy it!
What do I need in order to learn Linux?
- PC/Notebook (depending on Linux version that you would like to use I recommend: RAM – Min 4GB, CPU – Dual/Quad Core)
- Virtualization Software: Oracle VirtualBox (recommended and also free software) / VMWare (paid software)
- Ubuntu image file
Note: I do not recommend to install Linux (at this moment) as a SecondBoot or as a default operating system of your PC/notebook. What I recommend is to install Ubuntu on a Virtual Machine.
Basic Linux Commands and Syntax
This tutorial deals exclusively with the CLI (Command Line Interface). The CLI is a very powerful interface that allows the users to administer small devices, extremely capable cloud computer servers, network devices and everything between them.
A command is a software program and when executed on the CLI, performs an action on the computer. First of all install Ubuntu on the VirtualMachine Software, power on Ubuntu machine, login on the system and open the terminal window.
To execute a command, first type the command, for example ls, and hit Enter.
tsulthan@brainytux:~$ ls Downloads Pictures snap Public Templates Desktop Videos Documents Music
Note: The commands are case sensitive, so LS will not execute but ls will execute.
sulthan@brainytux:~$ LS LS: command not found
Most of the commands follow a simple syntax:command [options] [arguments]. You have to type the command followed by options and/or arguments and then press Enter. The options usually alter the behaviour of commands and arguments.
Arguments
An argument can be used to specify something that the command should act on. For example, you can try the following example:
Example: ls /var/log (ls = “list” lists the contents of directory /var/log)
In this example /var/log/ is the argument used with ls command.
sulthan@brainytux:~$ ls /var/log alternatives.log dist-upgrade gdm3 openvpn apt dmesg gpu-manager.log private auth.log dmesg.0 hp speech-dispatcher boot.log dmesg.1.gz installer syslog bootstrap.log dpkg.log journal ubuntu-advantage.log btmp faillog kern.log unattended-upgrades cups fontconfig.log lastlog wtmp
Options
Options are used to alter the behaviour of commands. In the next example, we will use -l option with ls command and see what happens.
Example: ls -l (-l = “long display”, means that will give more information). It will output detailed information about the listed files.
sulthan@brainytux:~$ ls -l total 34 drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Desktop drwxr-xr-x 5 sulthan sulthan 4096 Aug 8 00:27 Documents drwxr-xr-x 3 sulthan sulthan 4096 Aug 8 19:00 Downloads drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Music drwxr-xr-x 7 sulthan sulthan 4096 Aug 8 02:47 Pictures drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Public drwxr-xr-x 3 sulthan sulthan 4096 Aug 7 22:16 snap drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Templates drwxr-xr-x 8 sulthan sulthan 4096 Aug 7 23:46 Videos
Example: ls -r (-r “reverse”, it will reverse the alphabetical order)
sulthan@brainytux:~$ ls -r Music Documents Videos Desktop Templates Public snap Pictures Downloads
Options can be used at once, combined or separated, but the output will be the same. Order of the options does not matter.
Example: ls -r -l (separated)
sulthan@brainytux:~$ ls -r -l total 34 drwxr-xr-x 8 sulthan sulthan 4096 Aug 7 23:46 Videos drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Templates drwxr-xr-x 3 sulthan sulthan 4096 Aug 7 22:16 snap drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Public drwxr-xr-x 7 sulthan sulthan 4096 Aug 8 02:47 Pictures drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Music drwxr-xr-x 3 sulthan sulthan 4096 Aug 8 19:00 Downloads drwxr-xr-x 5 sulthan sulthan 4096 Aug 8 00:27 Documents drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Desktop
Example: ls -lr (combined)
sulthan@brainytux:~$ ls lr total 34 drwxr-xr-x 8 sulthan sulthan 4096 Aug 7 23:46 Videos drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Templates drwxr-xr-x 3 sulthan sulthan 4096 Aug 7 22:16 snap drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Public drwxr-xr-x 7 sulthan sulthan 4096 Aug 8 02:47 Pictures drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Music drwxr-xr-x 3 sulthan sulthan 4096 Aug 8 19:00 Downloads drwxr-xr-x 5 sulthan sulthan 4096 Aug 8 00:27 Documents drwxr-xr-x 2 sulthan sulthan 4096 Aug 7 21:53 Desktop
Printing Working Directory
To discover where we are located within file-system, we can use pwd command. We will use the term “Print” not to send information to a physical printer, but to send the information to be printed to the screen.
pwd [options]
sulthan@brainytux:~$ pwd /home/sulthan
Changing Directories
Directories are type of file used to store other files, they also provide hierarchical organization structure. To navigate the filesystem you can use the command cd (Change Directory).
cd [options] [path]
sulthan@brainytux:~$ cd Desktop sulthan@brainytux:~/Desktop$
Listing files
The ls command is used to list the contents of a directory.
ls [options][path]
To get more details about a file, like permissions, ownerships or timestamps, perform a longlisting using -l option with the ls command.
Example: ls -l /var/log
sulthan@brainytux:~$ ls -l /var/log total 5376 -rw-r--r-- 1 root root 37174 Aug 8 02:33 alternatives.log drwxr-xr-x 2 root root 4096 Aug 8 12:40 apt -rw-r----- 1 syslog adm 45255 Aug 8 19:30 auth.log -rw------- 1 root root 24051 Aug 8 09:56 boot.log -rw-r--r-- 1 root root 104003 Jul 31 21:57 bootstrap.log -rw-rw---- 1 root utmp 0 Jul 31 21:57 btmp drwxr-xr-x 2 root root 4096 Aug 7 21:52 cups drwxr-xr-x 2 root root 4096 Jul 21 05:53 dist-upgrade -rw-r--r-- 1 root adm 78208 Aug 8 09:57 dmesg -rw-r--r-- 1 root adm 79444 Aug 8 01:36 dmesg.0 -rw-r--r-- 1 root adm 19850 Aug 7 21:52 dmesg.1.gz -rw-r--r-- 1 root root 1395217 Aug 8 12:40 dpkg.log -rw-r--r-- 1 root root 32064 Aug 7 22:53 faillog -rw-r--r-- 1 root root 11126 Aug 8 02:33 fontconfig.log drwx--x--x 2 root gdm 4096 Oct 7 2019 gdm3 -rw-r--r-- 1 root root 1242 Aug 8 09:56 gpu-manager.log drwxr-xr-x 3 root root 4096 Jul 31 21:59 hp drwxr-xr-x 2 root root 4096 Aug 7 21:50 installer drwxr-sr-x+ 3 root systemd-journal 4096 Aug 7 21:51 journal -rw-r----- 1 syslog adm 767403 Aug 8 19:19 kern.log -rw-rw-r-- 1 root utmp 292584 Aug 7 22:53 lastlog drwxr-xr-x 2 root root 4096 Sep 5 2019 openvpn drwx------ 2 root root 4096 Jul 31 21:57 private drwx------ 2 speech-dispatcher root 4096 Jan 19 2020 speech-dispatcher -rw-r----- 1 syslog adm 2799670 Aug 8 19:42 syslog -rw------- 1 root root 0 Jul 31 21:57 ubuntu-advantage.log drwxr-x--- 2 root adm 4096 Aug 7 21:52 unattended-upgrades -rw-rw-r-- 1 root utmp 4992 Aug 8 10:10 wtmp
Each line contains the details about every file in the directory. The details are broken into columns separated by spaces.
File Types
The first column contains ten characters, the first character indicates the type of the file and the next nine characters indicates the file permissions:
d | directory | A file that contains other files
– | regular file | Readable, images, binary and compressed files
l | symbolic link | Points to other files
s | socket | Allows for the communication between processes
p | pipe | Allows for communication between processes
b | block file | Used to communicate with hardware
c | character file | Used to communicate with hardware
Permissions
Permissions indicate how users can access the files.
Hard Link Count
This number indicates how many hard links point to the file.
User Owner
When a file is created the ownership is automatically assigned to the user who created it.
Group Owner
Shows which group owns the file.
File Size
In case of a file, the size is displayed in bytes and in case of a directory, multiple of the block size used by the file system.
Timestamp
Indicates the time when the file’s content was last modified.
Filename
The last field contains the name of the file or directory.
Symbolic Links
Symbolic link name will be displayed along with an arrow and the link to the original file.
Sorting
The output of the ls command is sorted alphabetically by filename, but it can be modified by ls options. In the example below ls command will be combined with -l option so the relevant details to be displayed and with the -S option which sorts by size.
The -S option will sort the files by size.
The -r option will reverse the order of any type of sort.
