Basic Linux Commands
I am continue learning variety of DevOps technologies, including AWS, Linux, Python, Shell Scripting, Docker, Terraform, Jenkins, Git/GitHub, and Computer Networking. I have a strong ability to troubleshoot and resolve issues, and are consistently motivated to expand the knowledge and skills through exploration of new technologies.
I welcome you to this blog. We'll cover all the required Linux for getting started with DevOps or who wanna learns Linux in a very understandable manner.
Here, We cover the INTRODUCTION TO LINUX.
So let's start
INTRODUCTION TO LINUX Firstly, we have to know what is open source because Linux is Open Source.
What is Open Source? Open source: The software and source code are available to all. Anyone can inspect, modify, and enhance it. Many open-source licenses exist, each different in particular.
Linux Origins
1984: The GNU Project and the Free Software Foundation Creates an open-source version of UNIX utilities.
• Creates an open-source version of UNIX utilities.
• Creates the General Public License (GPL) Software license enforcing open source principles.
1991: Linus Torvalds
• Creates open-source, UNIX-like kernel, released under the GPL.
Today:
• Linux kernel + GNU utilities= complete, open-source, UNIX-like operating system.
• Packaged for targeted audiences as distributions.
Why Linux? • Open Source.
• Community support.
• Most Servers run on Linux.
• DevOps most of the tools are implemented on Linux only.
• Automation.
• Secure.
Architecture of Linux architecture of linux diagram hashnode.png
Linux Kernel receives a command from hardware and passes the signal from hardware to shell, from the shell we can execute commands and expect the return.
Different Linux distros ➔ Popular Desktop Linux OS(operating system)
• Ubuntu Linux
• Linux Mint
• Arch Linux
• Fedora
• Debian
• OpenSuse
➔ Popular Server Linux OS
• Red Hat Enterprise Linux
• Ubuntu Server
• Centos
• SUSE Enterprise Linux
Most used Linux distros currently in IT industry.
• RPM based:- RHEL & Centos.
• Debian based:- Ubuntu Server.
right rpm.pngDifference between RPM based and Debian based:
From the user’s point of view, there isn’t much difference between these tools. The RPM and DEB formats are both just archive files, with some metadata attached to them. DEB files are installation files for Debian-based distributions. RPM files are installation files for Red Hat based distributions. Ubuntu is based on Debian’s package management based on APT and DPKG. Red Hat, CentOS, and Fedora are based on the old Red Hat Linux package management system, RPM.
DEB or .deb (Debian based softwares)
DEB is the extension of the Debian software package format and the most often used name for such binary packages. DEB was developed by Bedian.
Example: Google chrome software
Package name: google-chrome-stable_current_amd64.deb
Installation: dpkg -i google-chrome-stable_current_amd64.deb
RPM or .rpm (Red Hat based software)
It is a package management system. The name RPM variously refers to the .rpm file format, files in this format, software packaged in such files, and the package manager itself. RPM was intended primarily for Linux distributions; the file format is the baseline package format of the Linux Standard Base. RPM was developed by Community & Red Hat.
Example: Google chrome software
Package Name: google-chrome-stable-57.0.2987.133-1.x86_64.rpm
Installation: rpm -ivh google-chrome-stable-57.0.2987.133-1.x86_64.rpm
NOTE: You will also encounter different commands, packages, and service names while using both kinds of distros.
Linux Commands: whoami - shows the current user
compgen -u - lists all the users
man (command name) - it's a guide with information about any command
echo "Hello world" - prints Hello world
echo "Hello" > filename → adds the text into the mentioned file
history - list of all commands we used till now
history 10 - list of the last 10 commands used
df -h - shows the disk-free space
Working with directories: ln -s /mnt/c/Users/Chris/Desktop - changes the directory to desktop
pwd - shows the current directory
cd - changes to the home directory
cd Desktop - changes to sub-directory
cd .. - changes to the parent directory
cd ~ - to go back to the default directory
Working with Files: touch demo.txt - creates a text file named demo in the current directory
touch (file1 name) (file2name)....(fileN name) - creates N number of files at a time in the current directory
ls - lists out all the files and folders in the current directory
cat demo.txt - opens a file
nano demo1.txt - creates a new file and also can modify the existing file.
vi demo.txt - modifies the contents of a file
less - opens a file in another window(same as nano)
Advanced Commands(Files): lsof - lists out all the open files
lsof -u [username] - lists out all the open files in a specific user
ls -a → list of all the files and folders including all hidden files and folders
cat -b (filename) - gives line numbers to lines only with text
cat -n (filename) - gives line numbers to even empty lines and to all lines with text in it
grep cH [file name] - returns the whole word containing that string or character mentioned in the command but case sensitive
grep -i cH [file name] - returns case insensitive
sed 's/chris/cgirs/' [file name] - replaces a word with another word within the command line only
sort (file name) - returns all the lines in alphabetical order of starting letters
sort -r (file name) - returns in reverse order
sort -n (file name) - returns in numerical order
cut -c1-2 (file name) - returns only the first 2 columns in a file
tar -cvf (filename) (source-folder) - to zip a .tar format file
tar -xvf (tar-file) - to unzip a .tar format file
To know more about ls commands, please click here
To know more about cat commands, please click here
Modifying file's/folder's directories: cp demo.txt Desktop - copies the mentioned file into the mentioned directory
mv demo.txt Desktop - moves the mentioned file to the mentioned directory and deletes it from the current directory
rm demo.txt - removes a file from the current directory(deletes)
Note: once used an rm command to remove a file, you can't undo it because there's no recycle bin in Linux. So please use the rm command carefully
mkdir (folder name) - creates a new directory(folder)
rmdir (folder name) - removes a directory(folder) only which is empty
rm -r (folder name) - removes a non-empty directory with its contents
Files and their Permissions: There are three types of permission:
read (r)
write (w)
execute (x)
These are generally represented as in rwx
These permissions affect three groups of owners:
user/owner (u)
group (g) → an entity among a user group
guests or other people (o)
ls -l - shows the file permissions for that mentioned file
chmod (+x or +w or +r) [file name] - changes any one of the permissions of a file
chmod u=rwx,g=rx,o=rw [filename] - changes all the permissions of a file at a time
chmod 777 [file name] - changes all permissions of a file to rwx
chown (username) [file name] - changes the owner of the file to that mentioned username.
Commands related to User-Id's and stuff:
id - will return the UserId, GroupId, groups belonging to the user etc
id -u (username) - will return only the UserId of that user
id -g (username) - will return only the GroupId of that user
Some of the commands with sudo: We use sudo when we are accessing root permissions
sudo bash - changes the author to root
su (user name) - gets back to the user as author
sudo apt-get install package - installs a package
sudo useradd (username) - adds a new user
sudo passwd (username) - adds a password to the user
sudo userdel (username) - deletes a user
sudo groupadd (group name) - adds a group of users
sudo groupdel (group name) - deletes a group of users
Networking commands: ifconfig - shows the ip address and some of the addresses of our device
ifconfig -a - shows all the interfaces in our device
ifconfig (port which we want to see) - shows the information only about port mentioned
ping google.com - checks whether google.com can communicate with us or not
ping (Ip addrs) - checks whether our system can communicate with ip addrs mentioned of another device connected to the same network as ours
wget (url) - will download the file in the url to the current directory only from http and https
curl (url) - to transfer data to or from a server, using any of the supported protocols (HTTP, FTP, IMAP, POP3, SCP, SFTP, SMTP, TFTP, TELNET, LDAP, or FILE).
nslookup google.com - will show the ip address and server address of google.com
I followed Udemy Course - Linux Administration Course and also followed Zero to Hero from trainwithshubham (Devops)
That's it for the blog guys. I hope you loved the reading!
Thank you 😊
