Here’s a cheat sheet of the core linux commands that I use daily.

Bash Commands

uname -a	Show system and kernel
head -n1 /etc/issue	Show distri­bution
mount	Show mounted filesy­stems
date	Show system date
uptime	Show uptime
whoami	Show your username
man command	Show manual for command
watch -n 1 'date'	Watch changes to the date each second then display output

 

Bash Variables

env	Show enviro­nment variables
export NAME=value	Set $NAME to value
$NAME	Output value of $NAME variable
$PATH	Executable search path
$HOME	Home directory
$SHELL	Current shell

 

Commmand Execution & IO

cmd, cmd1 and cmd2 refers to a command.

cmd1 ; cmd2	Run cmd1 then cmd2
cmd1 && cmd2	Run cmd2 if cmd1 is successful
cmd1 || cmd2	Run cmd2 if cmd1 is not successful
cmd &	Run cmd in a subshell
cmd1 | cmd2	Pipe stdout of cmd1 to cmd2
cmd1 | cmd2	Pipe stderr of cmd1 to cmd2
cmd < file	Input of cmd from file
cmd1 <(cmd2)	Output of cmd2 as file input to cmd1
cmd > file	Standard output stdout of cmd to file
cmd > /dev/null	Discard stdout of cmd
cmd >> file	Append stdout to file
cmd 2> file	Error output stderr of cmd to file
cmd &> file	Every output of cmd to file
cmd 1>&2	stdout to same place as stderr
cmd 2>&1	stderr to same place as stdout

 

Directories

pwd	Show current directory
mkdir dir	Make directory dir
cd dir	Change directory to dir
cd ..	Go up a directory
ls	List files

 

Files

touch file1	Create file1
cat file1 file2	Concat­enate files and output
less file1	View and paginate file1
file file1	Get type of file1
cp file1 file2	Copy file1 to file2
mv file1 file2	Move file1 to file2
rm file1	Delete file1
head file1	Show first 10 lines of file1
tail file1	Show last 10 lines of file1
tail -F file1	Output last lines of file1 as it changes

 

File Permis­sions

chmod 775 file	Change mode of file to 775
chmod -R 600 dir	Recurs­ively chmod dir to 600
chown user:group file	Change file owner to user and group to group

 

File Permission Bits

First digit is owner permis­sion, second is group and third is everyone. Calculate permission digits by adding numbers below.

4	read (r)
2	write (w)
1	execute (x)

 

ls Options

-a	Show all (including hidden)
-R	Recursive list
-r	Reverse order
-t	Sort by last modified
-S	Sort by file size
-l	Long listing format
-1	One file per line
-m	Comma-­sep­arated output
-Q	Quoted output

 

Search Files

grep pattern files	Search for pattern in files
grep -i	Case insens­itive search
grep -r	Recursive search
grep -v	Inverted search
grep -o	Show matched part of file only
find /dir/ -name name*	Find files starting with name in dir
find /dir/ -user name	Find files owned by name in dir
find /dir/ -mmin num	Find files modifed less than num minutes ago in dir
whereis command	Find binary for command
locate file	Find file (quick search of system index)

 

Processes

ps	Show snapshot of processes
top	Show real time processes
kill pid	Kill process with id pid
pkill name	Kill process with name name
killall name	Kill all processes with names beginning name