# Linux Commands

| **Command**              | **Description**                                                                                                                                            |
| ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `man <tool>`             | Opens man pages for the specified tool.                                                                                                                    |
| `<tool> -h`              | Prints the help page of the tool.                                                                                                                          |
| `apropos <keyword>`      | Searches through man pages' descriptions for instances of a given keyword.                                                                                 |
| `cat`                    | Concatenate and print files.                                                                                                                               |
| `whoami`                 | Displays current username.                                                                                                                                 |
| `id`                     | Returns users identity.                                                                                                                                    |
| `hostname`               | Sets or prints the name of the current host system.                                                                                                        |
| `uname`                  | Prints operating system name.                                                                                                                              |
| `pwd`                    | Returns working directory name.                                                                                                                            |
| `ifconfig`               | The `ifconfig` utility is used to assign or view an address to a network interface and/or configure network interface parameters.                          |
| `ip`                     | Ip is a utility to show or manipulate routing, network devices, interfaces, and tunnels.                                                                   |
| `netstat`                | Shows network status.                                                                                                                                      |
| `ss`                     | Another utility to investigate sockets.                                                                                                                    |
| `ps`                     | Shows process status.                                                                                                                                      |
| `who`                    | Displays who is logged in.                                                                                                                                 |
| `env`                    | Prints environment or sets and executes a command.                                                                                                         |
| `lsblk`                  | Lists block devices.                                                                                                                                       |
| `lsusb`                  | Lists USB devices.                                                                                                                                         |
| `lsof`                   | Lists opened files.                                                                                                                                        |
| `lspci`                  | Lists PCI devices.                                                                                                                                         |
| `sudo`                   | Execute command as a different user.                                                                                                                       |
| `su`                     | The `su` utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser). A shell is then executed. |
| `useradd`                | Creates a new user or update default new user information.                                                                                                 |
| `userdel`                | Deletes a user account and related files.                                                                                                                  |
| `usermod`                | Modifies a user account.                                                                                                                                   |
| `addgroup`               | Adds a group to the system.                                                                                                                                |
| `delgroup`               | Removes a group from the system.                                                                                                                           |
| `passwd`                 | Changes user password.                                                                                                                                     |
| `dpkg`                   | Install, remove and configure Debian-based packages.                                                                                                       |
| `apt`                    | High-level package management command-line utility.                                                                                                        |
| `aptitude`               | Alternative to `apt`.                                                                                                                                      |
| `snap`                   | Install, remove and configure snap packages.                                                                                                               |
| `gem`                    | Standard package manager for Ruby.                                                                                                                         |
| `pip`                    | Standard package manager for Python.                                                                                                                       |
| `git`                    | Revision control system command-line utility.                                                                                                              |
| `systemctl`              | Command-line based service and systemd control manager.                                                                                                    |
| `ps`                     | Prints a snapshot of the current processes.                                                                                                                |
| `journalctl`             | Query the systemd journal.                                                                                                                                 |
| `kill`                   | Sends a signal to a process.                                                                                                                               |
| `bg`                     | Puts a process into background.                                                                                                                            |
| `jobs`                   | Lists all processes that are running in the background.                                                                                                    |
| `fg`                     | Puts a process into the foreground.                                                                                                                        |
| `curl`                   | Command-line utility to transfer data from or to a server.                                                                                                 |
| `wget`                   | An alternative to `curl` that downloads files from FTP or HTTP(s) server.                                                                                  |
| `python3 -m http.server` | Starts a Python3 web server on TCP port 8000.                                                                                                              |
| `ls`                     | Lists directory contents.                                                                                                                                  |
| `cd`                     | Changes the directory.                                                                                                                                     |
| `clear`                  | Clears the terminal.                                                                                                                                       |
| `touch`                  | Creates an empty file.                                                                                                                                     |
| `mkdir`                  | Creates a directory.                                                                                                                                       |
| `tree`                   | Lists the contents of a directory recursively.                                                                                                             |
| `mv`                     | Move or rename files or directories.                                                                                                                       |
| `cp`                     | Copy files or directories.                                                                                                                                 |
| `nano`                   | Terminal based text editor.                                                                                                                                |
| `which`                  | Returns the path to a file or link.                                                                                                                        |
| `find`                   | Searches for files in a directory hierarchy.                                                                                                               |
| `updatedb`               | Updates the locale database for existing contents on the system.                                                                                           |
| `locate`                 | Uses the locale database to find contents on the system.                                                                                                   |
| `more`                   | Pager that is used to read STDOUT or files.                                                                                                                |
| `less`                   | An alternative to `more` with more features.                                                                                                               |
| `head`                   | Prints the first ten lines of STDOUT or a file.                                                                                                            |
| `tail`                   | Prints the last ten lines of STDOUT or a file.                                                                                                             |
| `sort`                   | Sorts the contents of STDOUT or a file.                                                                                                                    |
| `grep`                   | Searches for specific results that contain given patterns.                                                                                                 |
| `cut`                    | Removes sections from each line of files.                                                                                                                  |
| `tr`                     | Replaces certain characters.                                                                                                                               |
| `column`                 | Command-line based utility that formats its input into multiple columns.                                                                                   |
| `awk`                    | Pattern scanning and processing language.                                                                                                                  |
| `sed`                    | A stream editor for filtering and transforming text.                                                                                                       |
| `wc`                     | Prints newline, word, and byte counts for a given input.                                                                                                   |
| `chmod`                  | Changes permission of a file or directory.                                                                                                                 |
| `chown`                  | Changes the owner and group of a file or directory.                                                                                                        |