Linux Commands For Beginners

Are you looking for Linux Cheat Sheet? Or most used linux commands? I am putting up a list below for my own reference that could come in handy to you as and when you need it. I hope you like it!

System Info

• date – Display current date and time
• cal – show current month’s calender
• uptime – show current server’s uptime since last reboot
• w – display which user’s are logged in and average load on the server
• whoami – who you are logged in as (funny!)
• finder username – Get information about A specific user on the system
• uname – a – Display kernal information
• cat /proc/cpuinfo – Display CPU information
• cat /proc/meminfo – Display Memory (RAM) info
• man command – Show Manual for any “command”
• df – show disk usage
• du – show directory space usage
• df -h – show all HDD’s and their mount point
• free – show RAM and its swap usage (free -m to display in MB)
• whereis app – Find location of an app

Network

• ping – ping any IP / Host and output result
• whois domain.tld – Get whois information of any domain name
• dig domain.tld – Get DNS information of any domain
• dig -x host – Reverse lookup
• wget file-location – Download any remote file
• wget -c file – Continue a paused / stopped download

File Commands

• ls – List directories
• ls -al – Formatted listing with hidden files
• cd dir – Change to DIR
• cd – Switch to home
• pwd – Show current directory
• mkdir name – Create a new directory called “name”
• rm filename – Delete a file
• rm -r dir – Delete an EMPTY directory called “dir”
• rm -rf dir – Delete an entire directory with files called “dir”
• cp file1 file2 – Copy file1 to file2
• mv file1 file2 – Move or Rename a file
• touch file – Create or Update a file
• more file – Output the content of the file
• tail file – Output last 10 lines of a file

Compression

• tar cf file.tar files – Create a tarball compressing the folder called “files”
• tar xf file.tar – Exact the tarball “file.tar”
• gzip filename - Compress and rename the file to filename.gz

File Permissions

• 4 – Read (r)
• 2- Write (w)
• 1- Execute (x)
• Example : “chmod 777 filename” will allocation read, write & execute permission to filename.

Searching

• grep pattern files – search for a pattern in files
• grep -r pattern dir – Search recursively for pattern in dir
• command | grep pattern – Search for pattern in output command
• locate file – Find all instances of file

Process Management

• ps – Display all current active processes
• top – Display all running processes
• top -c – Display processes using top CPU
• top -m – Display processes using top Memory (RAM)
• kill pid – Kill a process with its pid
• bg – List stopped background jobs
• fg – Bring the most recent job to the foreground

SSH

• ssh user@hostname – connect to a host as a user
• ssh -p 22 user@host – Connect to a host as a user on specific port (in this case 22)
• ssh-copy-id user@host – Add your key to host for user to enable a keyed or password-less login

Shortcuts

• Ctrl + C – Halts the current command
• Ctril + Z – Stops the current command, you can resume it with fg in the foreground and bg in the background
• Ctril + D – Logout of current session
• Ctrl + U – Erase the line
• Ctrl + R – Type to bring up a recent command
• !! – Repeat the last command
• exit – Logout of current session
• abc* – Every file / dir / etc starting with abc

I hope you liked the sheet and will make use of it. In case you think I have forgotten anything, feel free to add it in the command and I will get the main sheet updated.