Linux Commands Reference

Prints the current working directory (full path from root).

Syntax: pwd [options]

Lists files and directories in the current directory.

Syntax: ls [options] [path]

Changes the current working directory to the specified path.

Syntax: cd [directory]

Moves up one directory level (to the parent directory).

Syntax: cd ..

Changes to the current user's home directory.

Syntax: cd ~

Switches back to the previous working directory.

Syntax: cd -

Saves the current directory and then changes to the specified directory.

Syntax: pushd [directory]

Returns to the directory saved by the last pushd command.

Syntax: popd

Displays the directory stack (list of directories saved with pushd).

Syntax: dirs [options]

Creates a new directory (folder). Use -p to create nested directories.

Syntax: mkdir [options] directory_name

Creates an empty file or updates the timestamp of an existing file.

Syntax: touch [options] filename

Copies files or directories from one location to another.

Syntax: cp [options] source destination

Moves or renames files and directories.

Syntax: mv [options] source destination

Removes (deletes) files or directories. Use -rf for recursive force delete.

Syntax: rm [options] file

Removes an empty directory. Safer than rm -r for removing directories.

Syntax: rmdir directory_name

Displays the entire contents of a file on the terminal.

Syntax: cat [options] filename

Views file contents page by page with forward and backward navigation.

Syntax: less filename

Views file contents one screen at a time (forward-only navigation).

Syntax: more filename

Displays the first 10 lines of a file by default. Use -n to specify count.

Syntax: head [options] filename

Displays the last 10 lines of a file. Use -f to follow file changes in real time.

Syntax: tail [options] filename

Opens a simple, beginner-friendly terminal text editor.

Syntax: nano filename

Opens the powerful Vim text editor for editing files.

Syntax: vim filename

Counts lines, words, and characters in a file.

Syntax: wc [options] filename

Creates links between files. Use -s for symbolic (soft) links.

Syntax: ln [options] source target

Displays detailed file and filesystem information (size, permissions, timestamps).

Syntax: stat filename

Determines and displays the file type (text, binary, image, etc.).

Syntax: file filename

Reads from stdin and writes to both stdout and one or more files simultaneously.

Syntax: command | tee filename

Compares two files line by line and shows the differences.

Syntax: diff [options] file1 file2

Displays the username of the currently logged-in user.

Syntax: whoami

Shows all users currently logged into the system with login details.

Syntax: who [options]

Displays who is logged in and what they are currently doing.

Syntax: w [username]

Prints user and group IDs (UID, GID) for the specified or current user.

Syntax: id [username]

Switches to another user account or the root user.

Syntax: su [options] [username]

Executes a command with superuser (root) privileges.

Syntax: sudo command

Changes the password for a user account.

Syntax: passwd [username]

Creates a new user account on the system.

Syntax: useradd [options] username

Modifies an existing user account (groups, shell, home directory, etc.).

Syntax: usermod [options] username

Deletes a user account. Use -r to also remove the home directory.

Syntax: userdel [options] username

Creates a new group on the system.

Syntax: groupadd groupname

Deletes an existing group from the system.

Syntax: groupdel groupname

Displays all groups the current user is a member of.

Syntax: groups [username]

Shows the last logged-in users from the system log file.

Syntax: last [options]

Changes the read, write, and execute permissions of files and directories.

Syntax: chmod [options] mode file

Changes the owner and/or group of a file or directory.

Syntax: chown [options] owner[:group] file

Changes the group ownership of a file or directory.

Syntax: chgrp [options] group file

Sets the default permission mask for newly created files and directories.

Syntax: umask [mode]

Displays the Access Control List (ACL) of a file or directory.

Syntax: getfacl filename

Sets or modifies the Access Control List (ACL) for a file or directory.

Syntax: setfacl [options] acl_spec file

Lists the allowed and forbidden sudo commands for the current user.

Syntax: sudo -l

Safely edits the /etc/sudoers file to configure sudo permissions.

Syntax: sudo visudo

Sends ICMP echo request packets to test network connectivity to a host.

Syntax: ping [options] host

Displays or configures network interface parameters (deprecated, use ip).

Syntax: ifconfig [interface]

Modern replacement for ifconfig. Shows and manipulates routing, devices, and tunnels.

Syntax: ip [options] object command

Displays network connections, routing tables, interface statistics, and more.

Syntax: netstat [options]

Modern replacement for netstat. Dumps socket statistics quickly.

Syntax: ss [options]

Transfers data from or to a server using various protocols (HTTP, FTP, etc.).

Syntax: curl [options] URL

Downloads files from the internet non-interactively via HTTP, HTTPS, or FTP.

Syntax: wget [options] URL

Performs DNS lookups and displays detailed name server query information.

Syntax: dig [options] domain

Queries DNS servers to resolve domain names to IP addresses and vice versa.

Syntax: nslookup [domain]

Simple utility for performing DNS lookups (forward and reverse).

Syntax: host [options] name

Traces and displays the route packets take to reach a network host.

Syntax: traceroute host

Displays and modifies the system's ARP cache (IP-to-MAC address mappings).

Syntax: arp [options]

Displays and modifies the IP routing table.

Syntax: route [options]

Shows or sets the system's hostname.

Syntax: hostname [new-name]

Displays and configures wireless network interface parameters.

Syntax: iwconfig [interface]

Network exploration tool and port scanner (basic usage).

Syntax: nmap [options] target

Reports a snapshot of current running processes with their PIDs.

Syntax: ps [options]

Displays an interactive, real-time view of system processes and resource usage.

Syntax: top

Enhanced, more user-friendly version of top with color and mouse support.

Syntax: htop

Sends a signal to terminate a process by its PID.

Syntax: kill [options] PID

Kills all processes matching a given name.

Syntax: killall [options] process_name

Sends a signal to processes based on name and other attributes.

Syntax: pkill [options] pattern

Resumes a suspended job in the background.

Syntax: bg [job_id]

Brings a background job to the foreground.

Syntax: fg [job_id]

Lists active jobs (background and suspended processes) in the current shell.

Syntax: jobs [options]

Runs a command with a specified scheduling priority (niceness value).

Syntax: nice -n priority command

Changes the priority (niceness) of an already running process.

Syntax: renice priority -p PID

Runs a command that keeps running even after the terminal session is closed.

Syntax: nohup command &

Searches for processes by name and returns their PIDs.

Syntax: pgrep [options] pattern

Prints system information such as kernel name, version, and architecture.

Syntax: uname [options]

Shows how long the system has been running along with load averages.

Syntax: uptime

Displays and changes the system hostname and related settings.

Syntax: hostnamectl [options]

Displays detailed CPU architecture information.

Syntax: lscpu

Lists information about all available block devices (disks and partitions).

Syntax: lsblk [options]

Lists all PCI devices connected to the system (graphics cards, network adapters).

Syntax: lspci [options]

Lists all USB devices connected to the system.

Syntax: lsusb [options]

Displays the amount of free and used system memory (RAM and swap).

Syntax: free [options]

Reports virtual memory statistics including CPU, memory, and I/O.

Syntax: vmstat [options] [interval]

Prints the kernel ring buffer messages (boot-time and hardware diagnostics).

Syntax: dmesg [options]

Lists all currently loaded kernel modules.

Syntax: lsmod

Displays detailed information about a specific kernel module.

Syntax: modinfo module_name

Displays all current environment variables.

Syntax: env

Prints text or the value of variables to the terminal.

Syntax: echo [options] [string]

Displays or sets the system date and time.

Syntax: date [options] [format]

Displays a calendar in the terminal.

Syntax: cal [month] [year]

Shows the list of previously executed commands in the current shell session.

Syntax: history [n]

Clears the terminal screen.

Syntax: clear

Creates or displays command aliases (shortcuts for longer commands).

Syntax: alias [name='command']

Removes a previously defined command alias.

Syntax: unalias name

Updates the local package index with the latest information from repositories.

Syntax: apt update

Upgrades all installed packages to their latest available versions.

Syntax: apt upgrade

Installs one or more packages from the repository.

Syntax: apt install package_name

Removes a package but keeps its configuration files.

Syntax: apt remove package_name

Removes a package along with all its configuration files.

Syntax: apt purge package_name

Removes packages that were automatically installed as dependencies and are no longer needed.

Syntax: apt autoremove

Searches for packages in the repository by keyword.

Syntax: apt search keyword

Displays detailed information about a specific package.

Syntax: apt show package_name

Lists packages based on package names with options for installed/upgradeable.

Syntax: apt list [options]

Installs a .deb package file directly (does not resolve dependencies).

Syntax: dpkg -i package.deb

Removes an installed package (keeps config files).

Syntax: dpkg -r package_name

Lists all installed packages with version and description.

Syntax: dpkg -l [pattern]

Installs a snap package from the Snap Store.

Syntax: snap install package_name

Installs Python packages from the Python Package Index (PyPI).

Syntax: pip install package_name

Archives multiple files into a single tarball. Use -czf to compress with gzip.

Syntax: tar [options] archive_name files

Compresses a single file using the gzip algorithm (replaces original with .gz).

Syntax: gzip [options] filename

Decompresses a .gz file back to its original form.

Syntax: gunzip filename.gz

Compresses files using the bzip2 algorithm (better compression than gzip, slower).

Syntax: bzip2 filename

Decompresses a .bz2 file back to its original form.

Syntax: bunzip2 filename.bz2

Creates a compressed ZIP archive of files and directories.

Syntax: zip [options] archive.zip files

Extracts files from a ZIP archive.

Syntax: unzip archive.zip

Compresses files using the xz (LZMA2) algorithm — very high compression ratio.

Syntax: xz filename

Decompresses a .xz file back to its original form.

Syntax: unxz filename.xz

High-compression archiver supporting many formats (7z, zip, rar, tar, etc.).

Syntax: 7z a archive.7z files

Connects securely to a remote machine via the SSH protocol.

Syntax: ssh [options] user@host

Securely copies files between local and remote hosts over SSH.

Syntax: scp [options] source destination

Efficiently syncs files and directories between two locations (local or remote).

Syntax: rsync [options] source destination

Transfers files to and from a remote host using the File Transfer Protocol.

Syntax: ftp host

Securely transfers files over SSH (interactive FTP-like interface).

Syntax: sftp user@host

Connects to a remote host via the Telnet protocol (unencrypted — prefer SSH).

Syntax: telnet host port

Generates SSH public/private key pairs for passwordless authentication.

Syntax: ssh-keygen [options]

Copies your SSH public key to a remote server for key-based authentication.

Syntax: ssh-copy-id user@host

Searches for files and directories in a directory hierarchy by name, type, size, etc.

Syntax: find [path] [expression]

Searches for patterns (text or regex) inside files and prints matching lines.

Syntax: grep [options] pattern file

Quickly finds files by name using a pre-built database (run updatedb to refresh).

Syntax: locate [options] pattern

Shows the full path of the executable that would run for a given command.

Syntax: which command

Locates the binary, source, and manual page files for a command.

Syntax: whereis command

Displays how a command name would be interpreted (alias, builtin, external, etc.).

Syntax: type command

Powerful text processing language for pattern scanning and data extraction.

Syntax: awk 'pattern { action }' file

Stream editor for filtering and transforming text (find/replace, insert, delete).

Syntax: sed [options] 'command' file

Sorts lines of text files alphabetically or numerically.

Syntax: sort [options] file

Reports or filters out repeated lines in a sorted file.

Syntax: uniq [options] file

Extracts specific columns/fields from each line of a file.

Syntax: cut [options] file

Translates, deletes, or squeezes characters from standard input.

Syntax: tr [options] set1 set2

Builds and executes command lines from standard input (useful with pipes).

Syntax: xargs [options] command

Reports disk space usage for all mounted filesystems (human-readable with -h).

Syntax: df [options]

Estimates file and directory space usage (disk usage).

Syntax: du [options] [path]

Manipulates disk partition table (create, delete, resize partitions).

Syntax: fdisk [options] device

Mounts a filesystem (attaches a device to the directory tree).

Syntax: mount [options] device mount_point

Unmounts a filesystem (detaches a mounted device from the directory tree).

Syntax: umount [options] mount_point

Creates a filesystem (formats) on a disk partition.

Syntax: mkfs -t type device

Checks and optionally repairs a filesystem for errors.

Syntax: fsck [options] device

Copies and converts raw data at the block level (disk cloning, bootable USB creation).

Syntax: dd if=input of=output [options]

Displays block device attributes including UUID and filesystem type.

Syntax: blkid [device]

Disk partitioning tool (supports GPT and MBR partition tables).

Syntax: parted [options] device

Interactive disk usage analyzer with a terminal UI (ncurses-based).

Syntax: ncdu [path]

Starts a systemd service immediately.

Syntax: systemctl start service_name

Stops a running systemd service immediately.

Syntax: systemctl stop service_name

Stops and then starts a systemd service.

Syntax: systemctl restart service_name

Enables a service to start automatically at boot time.

Syntax: systemctl enable service_name

Disables a service from starting automatically at boot.

Syntax: systemctl disable service_name

Shows the current status, recent logs, and PID of a systemd service.

Syntax: systemctl status service_name

Lists all loaded and active systemd units (services, mounts, sockets, etc.).

Syntax: systemctl list-units [options]

Legacy command to run SysV init scripts (works on both SysV and systemd).

Syntax: service service_name action

Queries and displays logs from the systemd journal.

Syntax: journalctl [options]