UNIX/Linux Basic Command Reference

File Commands

ls – directory listing

ls -all – formatted listing with hidden files

cd dir– change directory

cd– change to home

pwd– show current directory

mkdir dir– create a directory dir

rm file– delete file

rm -r dir– delete directory dir

rm -f file– force remove file

rm -rf dir– force remove directory dir*

cp file1 file2– copy file1 to file2

cp -r dir1 dir2 – copy dir1 -copy dir1 to dir2; create dir2 if it doesn’t exist

mv file1 file2– rename or move file1 to file2 if file2 is an existing directory, moves file1 into directory file2

ln -s file link– create symbolic link link to file

touch file– create or update file

cat > file-places standard input into file

more file– output the contents of file

head file– output the first 10 lines of file

tail file– output the last 10 lines of file

tail -f file– output the contents of file as it grows, starting with the last 10 lines

Process ManagementĀ 

ps-display your currently active process

top– display all running process

kill pid– kill process id pid

killall proc– kill all processes named proc *

bg– lists stopped or background jobs; resume a stopped job in the background

fg n– brings job n to the foreground


File Permission

chmod octal file– change permission of file to octal, which can be found separately for user,group, and world by adding:

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


chmod 777 – read, write, execute for all

chmod 755 – rwx for owner, rx for group and world, for more option see man chmod.



ssh user@host – connect to host as user

ssh -p port user@host – connect to host on port, port as user

ssh – copy-id user@host -add your key to host for user to enable a keyed or passwordless login



grep pattern files – search for pattern in files

grep -r pattern dir – search recursively for pattern in dir

command | grep pattern – search for pattern in the output of command

locate file – find all instances of file


System Info

date – show the current date and time

cal – show this month’s calender

uptime – show current uptime

W – display who is online

whoami – who you are logged in as

finger user – display information about user

uname -a – show kernel information

cat /proc/meminfo – memory information

man command – show the manualĀ  for command

df – show disk usage

du – show directory space usage

free – show memory and swap usage

whereis app – show possible locations of app

which app – show which app will be run by default



tar cf file.tar files – create a tar named file.tar containing files

tar xf file.tar – extract the files from file tar

tar czf file.tar.gz files – extract a tar using Gzip

tar cjf file.tar.bz2 – create a tar with Bzip2 compression


ping host – ping host and output results

whois domain – get whois information for domain

dig domain – get DNS information for domain

dig -x host – reverse lookup host

wget f – download file

wget -c file – continue a stopped download



install from source:

./configure make make install.

dpkg -i pkg.deb – install a package (Debian)

rpm -Uvh pkg.rpm – install a package (RPM)



Ctrl+C – halts the current command

Ctrl+Z – stops the current command resume with fg in the foreground or bg in the background

Ctrl+D – logout the current session similar to exit

Ctrl+W – erases one word in the current line

Ctrl+U – erases the whole line

Ctrl+R – type to bring up a recent command

!! – repeats the last command

exit – log out of current session