ls: Lists files and directories in the current directory. cd: Changes the current directory. pwd: Prints the current working directory. mkdir: Creates a new directory.   rmdir: Removes an empty directory. cp: Copies files or directories.   mv: Moves or renames files or directories. rm: Removes files or directories. touch: Creates an empty file or updates the timestamp of an existing file. cat: Displays the content of a file. less: Views the content of a file, one page at a time. head: Displays the first few lines of a file. tail: Displays the last few lines of a file. find: Searches for files in a directory hierarchy. grep: Searches for a specific pattern in files. chmod: Changes file or directory permissions. chown: Changes file or directory ownership. ln: Creates hard or symbolic links to files. df: Displays disk space usage. du: Shows disk usage of files and directories. top: Displays real-time system processes. ps: Shows running processes. kill: Terminates a process by PID. man: Displays the manual page for a command. history: Shows the history of commands you've run. sudo: Executes a command with superuser privileges. apt-get: Installs, updates, or removes packages on Debian-based systems. yum: Installs, updates, or removes packages on Red Hat-based systems. wget: Downloads files from the web. curl: Transfers data from or to a server using various protocols. ssh: Connects to a remote machine securely via SSH. ping: Tests connectivity to a network host. ifconfig: Displays or configures network interfaces. ip: Displays and manages network interfaces, routing, and more. netstat: Displays network connections, routing tables, and interface statistics. echo: Prints text to the terminal or writes text to files. date: Displays or sets the system date and time. shutdown: Shuts down or reboots the system. reboot: Reboots the system. alias: Creates a shortcut for a command. diff: Compares the contents of two files line by line. cmp: Compares two files byte by byte. sort: Sorts the lines of a file alphabetically or numerically. uniq: Removes duplicate lines from a sorted file. wc: Counts words, lines, and characters in a file. cut: Cuts sections from each line of a file or output. tr: Translates or deletes characters from input. xargs: Builds and executes command lines from standard input. tee: Reads from standard input and writes to both standard output and files. basename: Strips directory and suffix from filenames. dirname: Extracts the directory path from a file path. read: Reads input from the user or file. tar: Archives and extracts files using tar format. zip: Compresses files into a zip archive. unzip: Extracts files from a zip archive. gzip: Compresses files using the gzip format. gunzip: Decompresses gzip-compressed files. rsync: Synchronizes files and directories between two locations. iptables: Configures the IP packet filter rules of the Linux kernel. ufw: Simplified firewall management tool (Uncomplicated Firewall). systemctl: Controls the systemd system and service manager. journalctl: Views systemd logs. dmesg: Displays kernel ring buffer messages. who: Shows who is logged into the system. last: Displays a list of last logged-in users. at: Schedules a one-time task to run at a specific time. awk: Pattern scanning and processing language used for text processing. sed: Stream editor for filtering and transforming text. chroot: Changes the root directory for a command or shell. lsof: Lists open files and the processes that opened them. nc: A versatile networking tool often used for testing and debugging. sftp: A secure file transfer program over SSH. ncdu: Disk usage analyzer with a user-friendly interface. dig: Performs DNS lookups. nslookup: Queries DNS information. hostname: Displays or sets the system’s hostname. curl ifconfig.me: Gets your public IP address. adduser: Adds a new user to the system. deluser: Removes a user from the system. groupadd: Adds a new group to the system. usermod: Modifies user account details. groups: Displays the groups the current user belongs to. sudo su: Switches to the root user. nohup: Runs a command that will continue running after logging out. jobs: Lists all active jobs in the current session. fg: Brings a background job to the foreground. bg: Resumes a stopped job in the background. ctrl + z: Pauses a foreground job, allowing it to run in the background. locate: Quickly finds files by name. updatedb: Updates the database used by the locate command. alias ll='ls -la': Creates an alias ll for a long-format list of files. unalias: Removes an alias for a command. export: Sets or exports environment variables. env: Displays the current environment variables. crontab: Manages cron jobs for automating tasks. watch: Repeatedly runs a command at regular intervals. vmstat: Reports virtual memory statistics. mpstat: Displays CPU usage statistics. htop: An interactive process viewer (more user-friendly than top). uptime: Displays the system uptime and load average. ulimit: Displays or sets resource limits for user processes. ip link: Manages network interfaces. ss: A faster alternative to netstat for displaying network connections. traceroute: Traces the route packets take to a network host. ping6: Tests connectivity to a network host using IPv6. scp: Securely copies files between hosts over SSH. bc: A command-line calculator. dd: Converts and copies files, useful for creating disk images. arp: Displays or modifies the system's ARP table. md5sum: Computes and verifies MD5 hashes. sha256sum: Computes and verifies SHA-256 hashes. hostnamectl: Controls the system's hostname. ip a: Displays IP addresses of the system's network interfaces. ip r: Displays the routing table. journalctl -f: Follows the system logs in real time. tshark: A command-line network packet analyzer. lspci: Lists PCI devices connected to the system. lsusb: Lists USB devices connected to the system. modprobe: Adds or removes modules from the Linux kernel. parted: A disk partitioning tool. mkfs: Creates a file system on a partition or device. fsck: Checks and repairs a file system. tune2fs: Adjusts tunable file system parameters on ext filesystems. swapoff: Disables swap space on a device. swapon: Enables swap space on a device. fuser: Identifies processes using files or sockets. nmcli: Command-line tool for managing NetworkManager. w: Displays logged-in users and their active processes. wall: Sends a message to all logged-in users. passwd: Changes user passwords. stat: Displays detailed information about a file or file system. chage: Changes user password expiration information. pmap: Reports memory map of a process. ionice: Sets or gets I/O scheduling class and priority. nc (netcat): Reads and writes data across network connections. dstat: Combines and displays system resource statistics, such as CPU, disk, and network usage. sar: Collects, reports, or saves system activity information. iostat: Reports CPU and I/O statistics for devices and partitions. iotop: Displays real-time disk I/O usage by processes. inotifywait: Waits for changes to files or directories using inotify. inotifywatch: Watches for changes in a file or directory using inotify. nice: Runs a command with a modified scheduling priority. renice: Alters the priority of running processes. lsblk: Lists information about block devices. hdparm: Configures and displays information about SATA/IDE devices. smartctl: Monitors the health of hard drives using SMART. fallocate: Preallocates space to a file. wipe: Securely erases files or partitions. file: Determines file type based on content. shred: Securely deletes a file by overwriting it. ncftpput: Uploads files to an FTP server. ncftpget: Downloads files from an FTP server. ufw: Simplified firewall utility for managing iptables rules. ethtool: Configures and displays Ethernet device settings. brctl: Manages Ethernet bridges. xkill: Terminates a window by clicking on it. xrandr: Configures display screen resolution, rotation, and reflection. xset: Manages X display settings. xdg-open: Opens a file or URL in the user's preferred application. apropos: Searches the manual page names and descriptions for keywords. systemd-analyze: Displays system boot performance statistics. timedatectl: Manages system time and date settings. fwupdmgr: Firmware update manager for updating hardware firmware. lscpu: Displays information about the CPU architecture. getfacl: Displays file access control lists (ACLs). setfacl: Sets file access control lists (ACLs). pv: Monitors the progress of data through a pipeline. logrotate: Manages the automatic rotation and compression of log files. xclip: Interfaces with the X clipboard from the command line. cups: Manages printers (Common Unix Printing System). lp: Sends a file to the printer. lprm: Removes print jobs from the queue. lpstat: Displays the status of the print system. strace: Traces system calls and signals. tcpdump: Captures network traffic for analysis. envsubst: Substitutes environment variables in shell commands. tput: Initializes terminal capabilities, such as clearing the screen. xargs: Builds and executes command lines from standard input. dmesg | tail: Displays recent kernel messages (useful for hardware or system errors). lsns: Lists all active Linux namespaces. ss -tuln: Lists open network ports (TCP and UDP). iptables-save: Outputs current iptables rules to a file. iptables-restore: Restores iptables rules from a file. tac: Displays a file in reverse line order (opposite of cat). nl: Numbers the lines of a file. yes: Repeatedly outputs a string until stopped (e.g., yes y). split: Splits a file into pieces. csplit: Splits a file into pieces based on context. paste: Merges lines of files side by side. comm: Compares two sorted files line by line. shuf: Shuffles lines of text in random order. factor: Prints the prime factors of a given number. seq: Prints numbers in a sequence. pr: Converts text files for printing, adding headers and footers. column: Formats output into columns. od: Displays files in octal, decimal, hexadecimal, or ASCII. hexdump: Displays files in hexadecimal format. xxd: Creates a hex dump of a file or converts a hex dump back to binary. watch: Runs a command repeatedly, displaying the output and updates. timeout: Runs a command with a time limit. stdbuf: Alters the buffering of input/output for a command. rename: Renames files using a regular expression. prlimit: Displays or modifies resource limits of running processes. uuidgen: Generates a new universally unique identifier (UUID). vipw: Safely edits the /etc/passwd file. vigr: Safely edits the /etc/group file. getent: Retrieves entries from databases like passwd, group, or hosts. addgroup: Creates a new user group. pwgen: Generates random passwords. expire: Forces a password change after a specific period. showmount: Displays information about an NFS server. exportfs: Maintains the NFS server's exported file systems. rpcinfo: Displays information about RPC services on a networked system. lsmod: Lists currently loaded kernel modules. insmod: Inserts a module into the Linux kernel. rmmod: Removes a module from the Linux kernel. depmod: Generates modules dependency and map files. kmod: Interfaces with kernel modules from the command line. e2fsck: Checks the integrity of an ext2/ext3/ext4 file system. blkid: Displays block device attributes, including UUID. mount: Mounts a file system. umount: Unmounts a file system. parted: A command-line partition editor. gparted: A graphical partition editor (based on parted). cryptsetup: Manages encrypted devices. losetup: Configures loopback devices. mkswap: Sets up a swap area on a device or file. tmux: Terminal multiplexer for managing multiple terminal sessions. finger: Displays user information (if installed). lastb: Shows failed login attempts. pidof: Finds the process ID (PID) of a running program. pgrep: Searches for processes by name. curl -I: Fetches the HTTP headers from a URL. chattr: Changes file attributes on a Linux file system. lsattr: Lists file attributes on a Linux file system. join: Joins lines of two files based on a common field. tree: Displays a directory structure in a tree-like format. col: Filters reverse line feeds from input. free: Displays memory usage.