Linux is a free, open source, and Unix-like operating system built around the Linux Kernel first created by Linus Torvalds in 1991.It has since evolved into a powerful and versatile family of operating systems used worldwide. Linux is known for its stability, security, and customization capabilities. The operating system is built on the principles of free and open-source software, allowing users to access and modify the source code. Since it is free, and anyone can modify it and make their own distributions, it is extremely popular. Just like unix it also has similar notions of a kernel, shell, and utilities. There are various flavors of Linux such as Debian, OpenSUSE, Red Hat etc.
Here are a few basic commands:
| Command | Description | Example |
|---|---|---|
| ls | List directory contents | ls |
| cd | Change the current directory | cd /path/to/directory |
| pwd | Print the current working directory | pwd |
| cp | Copy files or directories | cp file.txt destination/ |
| mv | Move or rename files or directories | mv old_name new_name |
| rm | Remove files or directories | rm file.txt |
| mkdir | Create a new directory | mkdir new_directory |
| rmdir | Remove an empty directory | rmdir empty_directory |
| cat | Concatenate and display the content of files | cat file.txt |
| more | Display content one screen at a time | more file.txt |
| less | Display content with advanced features | less file.txt |
| head | Display the first few lines of a file | head -n 5 file.txt |
| tail | Display the last few lines of a file | tail -n 10 file.txt |
| touch | Create an empty file or update the access and modification time of a file | touch new_file.txt |
| chmod | Change file permissions | chmod 755 file.sh |
| chown | Change file owner and group | chown user:group file.txt |
| ps | Display information about running processes | ps aux |
| top | Display and update information about the top CPU processes | top |
| kill | Send a signal to a process | kill -9 process_id |
| df | Display disk space usage | df -h |
| du | Display file and directory space usage | du -h |
| free | Display amount of free and used memory in the system | free -h |
| uname | Display system information | uname -a |
| date | Display the current date and time | date |
| cal | Display a calendar for the current month or year | cal |
| echo | Display text or a variable | echo "Hello, Linux!" |
| grep | Search for a pattern in a file or stream | grep pattern file.txt |
| find | Search for files and directories in a directory hierarchy | find /path/to/search -name "filename" |
| locate | Find the location of files and directories | locate filename |
| wget | Download files from the internet | wget URL |
| curl | Transfer data from or to a server | curl URL |
| tar | Archives and extracts files from a tape or disk archive | tar -cvf archive.tar files/ |
| gzip | Compress files using gzip compression | gzip file.txt |
| gunzip | Decompress files compressed with gzip | gunzip file.txt.gz |
| ssh | Connect to a remote server using SSH | ssh user@hostname |
| scp | Copy files between a local and remote machine using SSH | scp file.txt user@remote:/path/to/destination/ |
| rsync | Sync files and directories between two locations | rsync -avz source/ destination/ |
| whoami | Display the username of the current user | whoami |
| passwd | Change user password | passwd |
| su | Switch user or become superuser | su username |
| sudo | Execute a command as the superuser or another user | sudo command |
| useradd | Add a new user account | useradd newuser |
| userdel | Delete a user account | userdel username |
| usermod | Modify a user account | usermod -aG groupname username |
| passwd | Change user password | passwd username |
| groups | Display the groups a user belongs to | groups username |
| id | Display user and group information | id username |
| history | Display command history | history |
| man | Display the manual for a command | man command |
| info | Display information about a command | info command |
| lsblk | List block devices, including disks and partitions | lsblk |
| lsusb | List USB devices connected to the system | lsusb |
# Install packages with Apt (Advanced Package Tool)
# Download the package lists from the repositories and update them to get information on the newest versions of packages and their dependencies. It will do this for all repositories and PPAs
sudo apt-get update
sudo apt-get -o Acquire::ForceIPv4=true update
# Do apt-get update but also fix missing packages
sudo apt-get update --fix-missing
sudo apt-get -o Acquire::ForceIPv4=true update --fix-missing
# Fetch new versions of packages existing on the machine if APT knows about these new versions, It will not install or remove packages
sudo apt-get upgrade
# Do a dist upgrade (not recommended) [ will do apt-get upgrade, but also try to intelligently handle the dependencies, so it might remove some obsolete packages or add new one)
sudo apt-get dist-upgrade
# To list all the packages installed
dpkg --list
# To know what version of a package is installed
# apt-cache policy [name of the package]
apt-cache policy vi
# To install a package
# sudo apt-get install [name of the package]
sudo apt-get install vim
sudo apt-get -o Acquire::ForceIPv4=true install vim
# To install a specific version of a package
# sudo apt-get install package=version
# To remove a package (not any of its configuration files or data files, or any of its dependencies)
# sudo apt-get remove packagename
# To remove a package (with its configuration files, data files, but not its dependencies)
# sudo apt-get purge packagename or apt-get --purge packagename
# To remove remove all dependencies that are no longer required
# sudo apt-get autoremove
# To remove a package purge all of its dependencies and configuration files
# sudo apt-get --purge autoremove packagename
sudo apt-get --purge autoremove nano
# Turning a shell script into binary
sudo apt-get install shc
shc -f script.sh
References: https://www.kernel.org/doc/man-pages/