Set of Commands Used in Linux and their Meaning

Learning Linux commands is one of the main concerns for any Linux beginner. Although, the improvement in GUI has made it possible to accomplish almost everything with a graphical interface the fact is you still need to know the Linux command line to get the most out of it. Here’s a Linux command quick reference guide along with meanings (what they do).

ls (Synopsis: s [options] [names])

Lists the contents of a directory.

mkdir (Synopsis: mkdir [OPTION] DIRECTORY)

Creates a (or more than one) new directory.

cp (Synopsis: cp [OPTION]… SOURCE… DIRECTORY)

Copy source to destination (to copy files)

mv (Synopsis: mv [OPTION]… SOURCE… DIRECTORY)

Move/rename files or directories

cal (synopsis: cal [-3jmy] [[month] year])

Displays a calendar

whoami (Synopsis: whoami [OPTION])

Displays the user id of the current user.

Tree (Synopsis: Tree [-OPTIONS])

Lists the contents of directories in a tree structure.

cat (Synopsis: cat [OPTION] [FILE])

Concatenate files.

uptime (Synopsis: Uptime /Uptime [-V])

Displays how long the system has been running.

pwd (Synopsis: pwd [OPTIONS])

Prints the name of the current directory

df (Synopsis: df [OPTION] ..[FILE])

displays disk space usage data

whereis (Synopsis: whereis [ -bmsu ] [ -BMS directory… -f ] filename)

Find the binary, source for specified files.

man (Synopsis: man [options] [section] [title])

Display the on-line reference manual.

Kill (Synopsis: kill [ -signal | -s signal ] pid)

Sends a signal to terminate a (or multiple) process IDs.

mount (Synopsis: mount [-lhV])

Mounts a file system.

grep (Synopsis: grep [OPTIONS] PATTERN [FILE…])

Searches for files matching a regular expression pattern.

chmod (Synopsis: chmod [OPTION]… MODE[,MODE]… FILE)

Changes the file mode bits.

ln (Synopsis: ln [OPTION]… TARGET)

Makes links between files.

top (Synopsis: top [options])

Displays the currently running Linux tasks.

cron (Synopsis: cron [-f] [-l] [-L loglevel])

Execute scheduled commands.

sudo (Synopsis: sudo [options] [command] )

Run a command as another user.

hostname (Synopsis: hostname [option] [nameofhost])

Display/set the host name of the system.

ssh (Synopsis: ssh [options] hostname [command])

A program to log into a remote machine and executing command on the remote machine.

rm (Synopsis: rm [OPTION]… FILE)

Remove specified files or directories.

ps (Synopsis: ps [Options])

Displays a snapshot of the current running processes.

locate (Synopsis: locate [options] pattern)

Search and displays file names matching the specified pattern

find (Synopsis: find [pathnames] [conditions])

Performs a search for files in a directory hierarchy.

w (Synopsis: w[Options] [user])

Displays which user is logged in and what they are doing.

finger (Synopsis: finger [options] users)

Displays information about the system users.

ping (Synopsis: ping [options] host)

A common tool to check if a remote system is online and responding.

gpg (Synopsis: gpg [options] command [options])

Encrypt and decrypt information using the OpenPGP encryption and signing tool.

atd (Synopsis: atd [options])

Run jobs that are queued for later execution

bash (Synopsis: bash [options] [file])

The GNU Bourne-Again Shell.

chattr (Synopsis: chattr [options] mode files)

Modify file attributes on Linux second extended file system.

chown (Synopsis: chown [OPTION]… [OWNER][:[GROUP]] FILE)

Change the ownership of files.

cksum (Synopsis: cksum [files] )

Displays CRC checksum and byte counts for a file.

clear (Synopsis: clear)

Clears the terminal display.

cmp (Synopsis: cmp [options] file1 file2 [skip1 [skip2]] )

Compares two files byte by byte.

date (Synopsis: date [OPTION] [+FORMAT])

Display/set the system date and time.

du (Synopsis: du [options] [directories])

Displays a summary of disk usage of each file, recursively for directories.

expr (Synopsis: expr [EXPRESSION])

Evaluates an expression and displays the result.

ftp (Synopsis: ftp [options] [hostname])

The internet file transfer tool to transfer files to and from a remote host.

halt (Synopsis: halt [options])

Shutdown or reboot the system.

iptables (Synopsis: iptables command [options])

A tool for IPv4 packet filtering. Used to setup and maintain the tables of IP packet filter rules in the Linux kernel.

join (Synopsis: join [options] file1 file2)

This command joins the lines of two files matching on a common field.

last (Synopsis: last [options] [user] [ttynumber])

Display a list of last logged in users.

netstat (Synopsis: netstat [options] [delay])

Displays information about the Linux networking subsystem.

passwd (Synopsis: passwd [options] [LOGIN])

Change the password for any user account.

pinky (Synopsis: pinky [options] [users])

A light weight finger program that displays user information.

stat (Synopsis: stat [option] file )

Prints file (or file system) status.