Linux command line cheat sheet

Move around

pwd

Print the folder you are in

ls -la

List all files with details, including hidden ones

cd <folder>

Go into a folder

cd ..

Go up one folder

cd -

Go back to the previous folder

Files and folders

mkdir -p a/b/c

Create a folder and any missing parents

touch <file>

Create an empty file or update its time

cp -r <from> <to>

Copy a file or a whole folder

mv <from> <to>

Move or rename

rm -r <folder>

Delete a folder and everything in it (no undo)

ln -s <target> <link>

Make a shortcut (symbolic link)

Read and search

cat <file>

Print a whole file

less <file>

Read a long file page by page (q to quit)

head -n 20 <file>

Show the first 20 lines

tail -f <file>

Follow a log file as it grows

grep -rn "text" .

Find text in all files, with line numbers

find . -name "*.log"

Find files by name

wc -l <file>

Count lines

Permissions

chmod +x <file>

Allow a file to run as a program

chmod 755 <file>

Owner: read, write, run. Others: read, run

chown user:group <file>

Change who owns a file

sudo <command>

Run a command as the administrator

Numbers: 4 = read, 2 = write, 1 = run. Add them for each of owner, group, others.

Processes and system

ps aux

List running processes

top

Live view of CPU and memory use

kill <pid>

Ask a process to stop

kill -9 <pid>

Force a process to stop

df -h

Free disk space

du -sh *

Size of each item in this folder

free -h

Memory in use

Network

ping <host>

Check that a machine answers

curl -I <url>

Show only the response headers of a web address

ss -tulpn

Show which program listens on which port

ssh user@host

Open a shell on another machine

scp <file> user@host:<path>

Copy a file to another machine

Pipes and redirects

a | b

Send the output of a into b

a > file

Write output to a file (replaces it)

a >> file

Add output to the end of a file

a 2>&1

Send errors to the same place as normal output

a | xargs b

Run b once for each line a prints