Commands
Most frequently used CLI (Terminal) commands on Linux
Commands used for System Information
Command(s) |
Sample Output |
DATE The simple “date” command displays the current date and time (including the day of the week, month, time, time zone, year).
Date TZ By default, “date” command uses the time zone defined in path “/etc/localtime”. Linux user can change the time zone via Terminal by using command “TZ”.
Date --set Linux allows its user to set the current date and time of the system manually.
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Example - This would set the system date to May 18, 2023 10:10 PM
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DF The command “df” shows the amount of disk space used and disk space available on every file system containing each filesystem’s name and its path.
The command “df -h” shows the same result as the command “df” but now the data is in a more human-readable format.
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FREE The command “free” displays the amount of free and used memory in the complete system.
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$ free
total used free shared buff/cache available
Mem: 16232800 4698636 6761664 59100 4772500 11205016
Swap: 2097152 0 2097152
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PS The command “ps” which is also known as the process status command is used to provide information about the processes currently running on the system, including their respective process identification numbers (PIDs)
PS AUX & PS -EF Both list all processes of all users. In that aspect Where they differ is output format specifier,
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UPTIME The command “uptime” provides information about how long the system has been running in one line. The result for this command includes the current time, the time duration system has been running, the number of users who are currently logged on, and the system load averages for the past 1, 5, and 15 minutes respectively.
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$ uptime
19:59:06 up 22 days, 20:17, 1 user, load average: 0.52, 0.39, 0.38 |
W The command “w” displays detailed information about the users who are logged into the system currently.
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$ w
20:00:25 up 22 days, 20:18, 1 user, load average: 0.44, 0.41, 0.38
USER TTY FROM LOGIN IDLE JCPU PCPU WHAT
tim :1 :1 07Feb23 xdm 2days 0.00s /usr/libexec/gdm-x-session --run-script env |
PASSWD The command “passwd” stands for password and it is used to change the password of the user.
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$ passwd tim
changing password for tim.
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully |
EXIT The command “exit” as the name says it is used to exit from the system and log out from the current user.
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$ exit
logout
Connection to 192.168.1.1 closed. |
SS The ss command is a modern replacement for the classic netstat command. You can use it on Linux to get statistics about your network connections.
Use the -ltn flags to list all listening ports on your system.
Use the following to see if a specific port is listening on your system. In this case, the source port (sport) and destination port (dport) is 80 or you can use the protocol name, http, instead.
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SHUTDOWN The command “shutdown” is used to shut down the system.
Note: The shutdown command needs superuser privileges. Hence, you should either be root or run the command with sudo.
Using the command with no flags will schedule a shutdown 1 minute from execution.
Use the following to IMMEDIATELY shutdown your system.
You can schedule a shutdown in future by providing the time argument either in +t format or in hh:mm format. For example, if you want to shutdown the system after 15 minutes, you can use this command:
If you want to shutdown the system at 6 PM in the afternoon, you can use it in the following manner:
Cancel a shutdown
Reboot a system
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$ sudo shutdown
Shutdown scheduled for Thu 2023-03-02 20:12:13 EST, use 'shutdown -c' to cancel. |
Commands used for File Handling
LS The command “ls” displays the list of all directories, folder, and files present in the current directory.
LS - LTR The above-mentioned command displays the name of directories, folders, files with their respective owner name, group’s name, and rights your user has over these.
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MKDIR The command “mkdir” allows users to create directories/folders in the system. The user running this command must have suitable rights over the parent directory to create a directory or they will receive an error. |
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RMDIR The command “rmdir” allows users to remove directories/folders from the system. The user running this command must have suitable rights over the parent directory to remove a directory AND the directory must not have any files or sub-directories within it or you will receive an error. |
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RM The command “rm” is used to remove files from a directory.
RM -RF Permanently deletes the specified directory and ALL files and sub-directories beneath the specified directory. Be VERY careful using this command as you can inadvertently delete your whole drive! |
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MV The command “mv” is used for two purposes
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CP The command “cp” is used to copy data from a source file to the destination file. Its function is almost like the command “mv”. The only difference is by using the command “cp” the source file is not removed from the directory after its data is moved to the destination file. |
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TOUCH Creates an empty file at the specified path with the specified name. Useful for creating a blank file you intend to edit with a CLI editor, such as VIM or NANO. |
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CAT The command “cat” is a reverse of the command “tac”. It is used to display each line of the file starting from the first row and finishing on its last row. This command is more frequently used than “tac”. |
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ECHO The command “echo” used to display any expression that is passed as an argument. |
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GREP The command “grep” is used to search for a text in the specified file/folder. |
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ZIP The command “zip” is used to compress one or more files and store them in a new file with .zip extension. |
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UNZIP The command “unzip” is used to decompress a .zip file and extract all the files within to current directory. |
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SUDO Sudo stands for SuperUser DO and is used to access restricted files and operations. By default, Linux restricts access to certain parts of the system preventing sensitive files from being compromised. The
sudo -i elevates the user to root for the remainder of the session rather than a command by command basis. |
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