Linux Help

Below is a summary of many commonly used Linux commands. There are several excellent tutorials and tools available online. Below is a list that we have compiled:

Linux Reference Material

Linux Training

Linux Basics

Linux Command Info

Linux Wikis

Linux Command References

File Commands

  • ls – directory listing

  • ls -al – formatted listing with hidden files

  • cd dir – change directory to dir

  • pwd – show current directory (Print Working Directory)

  • mkdir dir – create a directory dir

  • rm file – delete file

  • rm -r dir – delete directory dir and all its contents

  • rm -f file – force delete file

  • rm -rf dir – force delete directory dir and all its contents (use with caution)

  • cp file1 file2 – copy file1 to file2 (overwrites file2 if it exists)

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

  • mv file1 file2 – rename file1 to file2 (overwrites file2 if it exists)

  • mv file dir – move file into directory dir

  • ln -s file_or_dir link – create a symbolic link link pointing to file_or_dir

  • touch file – create empty file; if file exists, updates last-modified date

  • less file – view contents of file

  • head file – output first 10 lines of file

  • tail file – output last 10 lines of file

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

Process Management

  • ps – display your currnet active processes

  • top – display all running processes

  • kill pid – kill process id pid (numerical ID)

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

  • fg – brings the most recent job to the foreground

  • fg n – brings job n to the foreground

File Permissions

  • chmod mode file – change permissions of file to given mode; mode can be [ugoa...][[+-=][perms...]...]

    • u, g, o, a – specify the owner: user, group, other, or all

    • +, -, = – + adds given permissions to file, - removes given permissions from file, = sets given permissions on file

    • perms : r, w, x or any combination of the three – r means read permission, w means write permission, x means execute (file) or cd (directory) permission

Searching Within Files

These commands can be used to find content within files:

  • grep pattern files – print out lines containing pattern in files

  • grep -r pattern dir – print out lines containing pattern in all files found recursively descending into directory dir

  • command | grep pattern – print out lines from the output of command which contain pattern

System Info

  • date – show current date and time

  • cal – show this month’s calendar

  • cal year – show calendar for entire year

  • uptime – show how long the machine has been up

  • w – display users who are logged in

  • whoami – who you are logged in as

  • id – print all user ID information for yourself

  • finger user - display information about user

  • uname -a – show information about machine

  • cat /proc/cpuinfo – cpu information

  • cat /proc/meminfo – memory information

  • man command – show manual for command

  • df -h – show disk usage

  • free – show memory and swap usage

  • whereis command – show possible paths to command

  • which command – show absolute path to command

Compression

  • tar cf dir.tar dir – create a tar file named dir.tar containing all files in the directory dir

  • tar xf dir.tar – extract all files from dir.tar

  • tar zcf dir.tar.gz dir – create a gzipped tar file named dir.tar.gz containing all files in dir

  • tar zxf dir.tar.gz – extract all files from dir.tar.gz

  • tar jcf dir.tar.bz2 dir – create a tar file named dir.tar.bz2 compressed with bzip2 containing all files in dir

  • tar jxf dir.tar.bz2 – extract all files from dir.tar.bz2

  • gzip file – compress file and rename it file.gz

  • gzip -d file.gz – uncompress file.gz into file

Internet and Network

  • jwhois domain – print administrative and contact information for the owner of domain

  • dig domain – print DNS information for domain

  • dig -x host – print reverse DNS lookup of host

  • wget url – download the file at url

  • wget -c url – resume a stopped download

Package Installation from Source

Typical GNU-style source packages for software follow this recipe for building:

$ ./configure --prefix=$HOME/dir
$ make
$ make install

You can also read our in-depth guide to compiling software on DEAC, for software packages that require considerably more work than this.

Other Useful Commands

  • Ctrl-C – halts the current command (send signal SIGINT)

  • Ctrl-Z – pauses the current command

  • fg – resumes a Ctrl-Z’ed command

  • bg – resumes a Ctrl-Z’ed command into the background (returning terminal control)

  • !! – repeats the last command

  • Up and Down keys on your keyboard – browse command history