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Common Linux Commands and their Meaning

written by: •edited by: Christian Cawley•updated: 5/24/2011

Listing the common Linux commands and their usages, here we outline for you a Linux command quick reference guide.

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    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.

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    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.