# Linux commands

## **Table of contents**

* [1\. File and Directory Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-1-file-and-directory-management)
    
* [2\. File Permissions and Ownership](https://alimasiuzama.hashnode.dev/linux-commands#heading-2-file-permissions-and-ownership)
    
* [3\. Process Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-3-process-management)
    
* [4\. Disk and System Information](https://alimasiuzama.hashnode.dev/linux-commands#heading-4-disk-and-system-information)
    
* [5\. Networking](https://alimasiuzama.hashnode.dev/linux-commands#heading-5-networking)
    
* [6\. User Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-6-user-management)
    
* [7\. Archiving and Compression](https://alimasiuzama.hashnode.dev/linux-commands#heading-7-archiving-and-compression)
    
* [8\. Package Management (Depends on the Distribution)](https://alimasiuzama.hashnode.dev/linux-commands#heading-8-package-management-depends-on-the-distribution)
    
* [9\. System Monitoring](https://alimasiuzama.hashnode.dev/linux-commands#heading-9-system-monitoring)
    
* [10\. Shutdown/Restart](https://alimasiuzama.hashnode.dev/linux-commands#heading-10-shutdownrestart)
    
* [11\. Advanced File Operations](https://alimasiuzama.hashnode.dev/linux-commands#heading-11-advanced-file-operations)
    
* [12\. Disk and Partition Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-12-disk-and-partition-management)
    
* [13\. System Resource and Performance Monitoring](https://alimasiuzama.hashnode.dev/linux-commands#heading-13-system-resource-and-performance-monitoring)
    
* [14\. Networking and Internet Tools](https://alimasiuzama.hashnode.dev/linux-commands#heading-14-networking-and-internet-tools)
    
* [15\. System Logs and Debugging](https://alimasiuzama.hashnode.dev/linux-commands#heading-15-system-logs-and-debugging)
    
* [16\. Scripting and Automation](https://alimasiuzama.hashnode.dev/linux-commands#heading-16-scripting-and-automation)
    
* [17\. Security and Permissions](https://alimasiuzama.hashnode.dev/linux-commands#heading-17-security-and-permissions)
    
* [18\. Backup and Recovery](https://alimasiuzama.hashnode.dev/linux-commands#heading-18-backup-and-recovery)
    
* [19\. Virtualization and Containers](https://alimasiuzama.hashnode.dev/linux-commands#heading-19-virtualization-and-containers)
    
* [20\. System Control and Administration](https://alimasiuzama.hashnode.dev/linux-commands#heading-20-system-control-and-administration)
    
* [21\. Networking Tools](https://alimasiuzama.hashnode.dev/linux-commands#heading-21-networking-tools)
    
* [22\. Filesystem and Storage Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-22-filesystem-and-storage-management)
    
* [23\. Development and Debugging Tools](https://alimasiuzama.hashnode.dev/linux-commands#heading-23-development-and-debugging-tools)
    
* [24\. Package Management Tools](https://alimasiuzama.hashnode.dev/linux-commands#heading-24-package-management-tools)
    
* [25\. Containers and Virtualization](https://alimasiuzama.hashnode.dev/linux-commands#heading-25-containers-and-virtualization)
    
* [26\. Performance Monitoring](https://alimasiuzama.hashnode.dev/linux-commands#heading-26-performance-monitoring)
    
* [27\. Security and Cryptography](https://alimasiuzama.hashnode.dev/linux-commands#heading-27-security-and-cryptography)
    
* [28\. Miscellaneous](https://alimasiuzama.hashnode.dev/linux-commands#heading-28-miscellaneous)
    
* [30\. Specialized File Management Commands](https://alimasiuzama.hashnode.dev/linux-commands#heading-30-specialized-file-management-commands)
    
* [31\. Advanced Scripting and Text Processing](https://alimasiuzama.hashnode.dev/linux-commands#heading-31-advanced-scripting-and-text-processing)
    
* [32\. Terminal Utilities and Shortcuts](https://alimasiuzama.hashnode.dev/linux-commands#heading-32-terminal-utilities-and-shortcuts)
    
* [33\. System Monitoring and Information](https://alimasiuzama.hashnode.dev/linux-commands#heading-33-system-monitoring-and-information)
    
* [34\. Networking and Connectivity Tools](https://alimasiuzama.hashnode.dev/linux-commands#heading-34-networking-and-connectivity-tools)
    
* [35\. Process and System Control](https://alimasiuzama.hashnode.dev/linux-commands#heading-35-process-and-system-control)
    
* [36\. User and Group Management](https://alimasiuzama.hashnode.dev/linux-commands#heading-36-user-and-group-management)
    
* [37\. System Maintenance and Troubleshooting](https://alimasiuzama.hashnode.dev/linux-commands#heading-37-system-maintenance-and-troubleshooting)
    
* [38\. Archiving and Compression](https://alimasiuzama.hashnode.dev/linux-commands#heading-38-archiving-and-compression)
    
* [39\. Date and Time](https://alimasiuzama.hashnode.dev/linux-commands#heading-39-date-and-time)
    
* [40\. Miscellaneous Useful Commands](https://alimasiuzama.hashnode.dev/linux-commands#heading-40-miscellaneous-useful-commands)
    

**Show less**

Here are some important Linux commands that are widely used for file management, system navigation, user management, and system administration:

### 1\. **File and Directory Management**

* `ls`: Lists files and directories in the current directory.
    
    * Example: `ls -l` (detailed list), `ls -a` (includes hidden files)
        
* `cd`: Changes the current directory.
    
    * Example: `cd /home/user` (navigate to `/home/user`)
        
* `pwd`: Prints the current working directory.
    
    * Example: `pwd`
        
* `mkdir`: Creates a new directory.
    
    * Example: `mkdir new_directory`
        
* `rmdir`: Removes an empty directory.
    
    * Example: `rmdir empty_directory`
        
* `rm`: Removes files or directories.
    
    * Example: `rm file.txt`, `rm -r directory_name` (removes directory with content)
        
* `cp`: Copies files or directories.
    
    * Example: `cp file1.txt file2.txt`, `cp -r dir1 dir2`
        
* `mv`: Moves or renames files or directories.
    
    * Example: `mv oldname.txt newname.txt`
        
* `touch`: Creates an empty file or updates file timestamp.
    
    * Example: `touch file.txt`
        
* `cat`: Displays content of a file.
    
    * Example: `cat file.txt`
        
* `nano`, `vim`: Opens file in text editors.
    
    * Example: `nano file.txt`, `vim file.txt`
        
* `find`: Finds files and directories.
    
    * Example: `find / -name filename.txt`
        
* `grep`: Searches for patterns within files.
    
    * Example: `grep 'pattern' file.txt`, `grep -r 'pattern' /path/to/directory`
        

### 2\. **File Permissions and Ownership**

* `chmod`: Changes file permissions.
    
    * Example: `chmod 755 file.txt`, `chmod u+x` [`script.sh`](http://script.sh/)
        
* `chown`: Changes file ownership.
    
    * Example: `chown user:group file.txt`
        
* `chgrp`: Changes the group ownership of a file.
    
    * Example: `chgrp groupname file.txt`
        

### 3\. **Process Management**

* `ps`: Displays currently running processes.
    
    * Example: `ps aux`, `ps -ef`
        
* `top`: Displays real-time system processes and resource usage.
    
* `kill`: Terminates a process by its process ID (PID).
    
    * Example: `kill 12345`, `kill -9 12345` (force kill)
        
* `pkill`: Terminates processes by name.
    
    * Example: `pkill firefox`
        
* `bg` / `fg`: Sends jobs to background (`bg`) or foreground (`fg`).
    

### 4\. **Disk and System Information**

* `df`: Displays disk space usage.
    
    * Example: `df -h`
        
* `du`: Shows the size of files and directories.
    
    * Example: `du -sh directory_name`
        
* `free`: Displays memory usage.
    
    * Example: `free -h`
        
* `uname`: Displays system information.
    
    * Example: `uname -a`
        
* `uptime`: Shows how long the system has been running.
    
* `dmesg`: Prints kernel and boot messages.
    
* `who`: Shows who is logged in.
    
* `w`: Displays system uptime and logged-in users.
    

### 5\. **Networking**

* `ifconfig`: Displays network interfaces and IP addresses.
    
    * Example: `ifconfig eth0`
        
* `ping`: Sends ICMP echo request to a host.
    
    * Example: `ping` [`google.com`](http://google.com/)
        
* `netstat`: Displays network connections, routing tables, and interface statistics.
    
* `ssh`: Securely connects to a remote machine.
    
    * Example: `ssh user@hostname`
        
* `scp`: Copies files between local and remote systems.
    
    * Example: `scp file.txt user@remote:/path/to/destination`
        
* `wget` / `curl`: Downloads files from the web.
    
    * Example: `wget` [`http://example.com/file`](http://example.com/file), `curl -O` [`http://example.com/file`](http://example.com/file)
        
* `ip`: Shows/manages network configurations.
    
    * Example: `ip a`, `ip link show`
        

### 6\. **User Management**

* `useradd`: Adds a new user.
    
    * Example: `sudo useradd username`
        
* `passwd`: Changes the password for a user.
    
    * Example: `passwd username`
        
* `usermod`: Modifies an existing user account.
    
    * Example: `usermod -aG sudo username` (add user to sudo group)
        
* `userdel`: Deletes a user account.
    
    * Example: `userdel username`
        
* `groupadd`: Creates a new group.
    
    * Example: `groupadd groupname`
        
* `groups`: Displays group memberships of a user.
    
    * Example: `groups username`
        

### 7\. **Archiving and Compression**

* `tar`: Archives files into a tarball (optionally compressed with gzip or bzip2).
    
    * Example: `tar -cvf archive.tar file1 file2`, `tar -xvf archive.tar`
        
    * Example with compression: `tar -czvf archive.tar.gz directory/`
        
* `gzip`: Compresses files.
    
    * Example: `gzip file.txt`, `gunzip file.txt.gz`
        
* `zip` / `unzip`: Compresses and extracts ZIP archives.
    
    * Example: `zip` [`archive.zip`](http://archive.zip/) `file.txt`, `unzip` [`archive.zip`](http://archive.zip/)
        

### 8\. **Package Management (Depends on the Distribution)**

* For Debian/Ubuntu-based systems:
    
    * `apt-get install`: Installs a package.
        
        * Example: `sudo apt-get install package_name`
            
    * `apt-get update`: Updates the package index.
        
        * Example: `sudo apt-get update`
            
    * `apt-get upgrade`: Upgrades installed packages.
        
        * Example: `sudo apt-get upgrade`
            
* For Red Hat/CentOS-based systems:
    
    * `yum install`: Installs a package.
        
        * Example: `sudo yum install package_name`
            
    * `yum update`: Updates the package index and upgrades packages.
        
        * Example: `sudo yum update`
            

### 9\. **System Monitoring**

* `htop`: Interactive process viewer.
    
* `iostat`: Reports CPU, disk I/O, and network usage.
    
* `vmstat`: Reports virtual memory statistics.
    
* `sar`: Collects and reports system activity.
    

### 10\. **Shutdown/Restart**

* `shutdown`: Shuts down or reboots the system.
    
    * Example: `shutdown -h now` (shutdown), `shutdown -r now` (reboot)
        
* `reboot`: Reboots the system immediately.
    
    * Example: `sudo reboot`
        
* `halt`: Halts the system immediately.
    
    * Example: `sudo halt`
        

### 11\. **Advanced File Operations**

* `stat`: Displays detailed information about a file or file system.
    
    * Example: `stat file.txt`
        
* `ln`: Creates hard or symbolic links to files.
    
    * Example: `ln file.txt link_to_file.txt` (hard link), `ln -s file.txt symlink.txt` (symbolic link)
        
* `basename` / `dirname`: Extracts filename or directory path from a given path.
    
    * Example: `basename /home/user/file.txt` (outputs `file.txt`)
        
    * Example: `dirname /home/user/file.txt` (outputs `/home/user`)
        

### 12\. **Disk and Partition Management**

* `fdisk`: Used to view and manage disk partitions.
    
    * Example: `fdisk /dev/sda`
        
* `parted`: Another tool for partition management, especially for large disks.
    
    * Example: `parted /dev/sda`
        
* `mkfs`: Formats a partition with a specified filesystem.
    
    * Example: `mkfs.ext4 /dev/sda1`
        
* `mount` / `umount`: Mounts or unmounts a file system.
    
    * Example: `mount /dev/sda1 /mnt`, `umount /mnt`
        
* `blkid`: Shows UUIDs and details about block devices.
    
    * Example: `blkid /dev/sda1`
        
* `lsblk`: Lists information about block devices (disks and partitions).
    
    * Example: `lsblk`
        

### **13\. System Resource and Performance Monitoring**

* `iotop`: Displays real-time disk I/O usage.
    
    * Example: `sudo iotop`
        
* `strace`: Traces system calls and signals used by a command.
    
    * Example: `strace -p <PID>`, `strace ls`
        
* `lsof`: Lists open files and the processes that opened them (useful for checking which files are in use).
    
    * Example: `lsof | grep filename`, `lsof -i :80` (lists processes using port 80)
        
* `ncdu`: Disk usage analyzer, an easy-to-read alternative to `du`.
    
    * Example: `ncdu /home`
        
* `sysctl`: Views or modifies kernel parameters.
    
    * Example: `sysctl -a` (shows all kernel parameters), `sysctl vm.swappiness=10` (changes swappiness parameter)
        
* `watch`: Runs a command repeatedly at regular intervals and displays the output.
    
    * Example: `watch -n 5 df -h` (runs `df -h` every 5 seconds)
        

### 14\. **Networking and Internet Tools**

* `traceroute`: Tracks the route packets take to a network host.
    
    * Example: `traceroute` [`google.com`](http://google.com/)
        
* `nc` (netcat): Reads and writes data across network connections (a Swiss-army knife for network-related tasks).
    
    * Example: `nc -l 12345` (listens on port 12345), `nc` [`google.com`](http://google.com/) `80` (connects to google on port 80)
        
* `dig`: DNS lookup utility (more advanced than `nslookup`).
    
    * Example: `dig` [`google.com`](http://google.com/)
        
* `hostname`: Shows or sets the system's hostname.
    
    * Example: `hostname`, `hostnamectl set-hostname newhostname`
        
* `arp`: Shows the system's ARP (Address Resolution Protocol) table.
    
    * Example: `arp -a`
        
* `ss`: Displays socket statistics, more modern than `netstat`.
    
    * Example: `ss -tuln` (shows open ports and services)
        

### 15\. **System Logs and Debugging**

* `journalctl`: Views system logs on `systemd` systems.
    
    * Example: `journalctl -xe` (view recent logs with errors), `journalctl -b` (view logs since last boot)
        
* `tail`: Displays the last lines of a file (often used for logs).
    
    * Example: `tail -f /var/log/syslog` (live view of log file)
        
* `dstat`: Combines the functionality of `vmstat`, `iostat`, and `netstat` in real-time.
    
    * Example: `dstat`
        
* `last`: Shows the login history of users.
    
    * Example: `last`
        
* `logrotate`: Rotates, compresses, and removes old logs automatically (usually run in cron jobs).
    

### 16\. **Scripting and Automation**

* `cron`: Schedules tasks to run periodically (using `crontab`).
    
    * Example: `crontab -e` (edit user crontab), `crontab -l` (list cron jobs)
        
* `at`: Schedules a task to run at a specific time (only once).
    
    * Example: `echo "shutdown -h now" | at 22:00`
        
* `alias`: Creates shortcuts for long commands.
    
    * Example: `alias ll='ls -lah'`
        
* `export`: Exports an environment variable.
    
    * Example: `export PATH=$PATH:/usr/local/bin`
        
* `source`: Executes commands from a file in the current shell.
    
    * Example: `source ~/.bashrc`
        
* `awk`: A powerful text processing tool for extracting and manipulating text.
    
    * Example: `awk '{print $1}' file.txt`
        
* `sed`: Stream editor for filtering and transforming text.
    
    * Example: `sed 's/oldtext/newtext/g' file.txt`
        

### 17\. **Security and Permissions**

* `sudo`: Runs a command as the superuser (root).
    
    * Example: `sudo apt-get update`
        
* `su`: Switches to another user.
    
    * Example: `su - username`
        
* `umask`: Sets default permissions for newly created files and directories.
    
    * Example: `umask 022`
        
* `setfacl` / `getfacl`: Manages Access Control Lists (ACLs) for fine-grained file permissions.
    
    * Example: `setfacl -m u:username:rwx file.txt`, `getfacl file.txt`
        

### 18\. **Backup and Recovery**

* `rsync`: Synchronizes files and directories between two locations efficiently.
    
    * Example: `rsync -avh /source/ /destination/`
        
* `dd`: Copies and converts files at a low level, often used for backups or disk cloning.
    
    * Example: `dd if=/dev/sda of=/path/to/backup.img bs=64K`
        
* `fsck`: Checks and repairs file system consistency.
    
    * Example: `fsck /dev/sda1`
        

### 19\. **Virtualization and Containers**

* `docker`: Manages containerized applications.
    
    * Example: `docker run -it ubuntu bash`, `docker ps` (list running containers)
        
* `virt-install`: Installs virtual machines via command line (for `libvirt`/KVM).
    
    * Example: `virt-install --name vm1 --ram 1024 --vcpus 1 --disk path=/var/lib/libvirt/images/vm1.img,size=10`
        
* `vagrant`: Automates the setup of virtualized development environments.
    
    * Example: `vagrant up`, `vagrant ssh`
        

### 20\. **System Control and Administration**

* `systemctl`: Manages systemd services (starting, stopping, enabling, disabling services).
    
    * Example: `systemctl start apache2`, `systemctl enable apache2`, `systemctl status apache2`
        
* `timedatectl`: Configures date, time, and timezone settings.
    
    * Example: `timedatectl set-timezone America/New_York`
        
* `hostnamectl`: Changes the system hostname and related settings.
    
    * Example: `hostnamectl set-hostname newhostname`
        
* `modprobe`: Loads or unloads kernel modules.
    
    * Example: `modprobe module_name`
        
* `sysfs`: Interacts with system hardware information exposed through `/sys`.
    
    * Example: `cat /sys/class/net/eth0/speed`
        

### 21\. **Networking Tools**

* `mtr`: Combines the functionality of `traceroute` and `ping` to diagnose network issues.
    
    * Example: `mtr` [`google.com`](http://google.com/)
        
* `iftop`: Displays bandwidth usage by network interface.
    
    * Example: `sudo iftop -i eth0`
        
* `tcpdump`: Captures and analyzes network packets.
    
    * Example: `sudo tcpdump -i eth0`, `tcpdump port 80`
        
* `iptraf-ng`: An interactive, real-time network monitoring utility.
    
* `ethtool`: Displays or changes network interface card (NIC) settings.
    
    * Example: `sudo ethtool eth0`
        
* `ufw`: Manages uncomplicated firewall settings (commonly used in Ubuntu).
    
    * Example: `sudo ufw allow 22`, `sudo ufw enable`
        
* `firewalld`: Firewall management tool used in RedHat/CentOS.
    
    * Example: `sudo firewall-cmd --permanent --add-port=8080/tcp`
        

### 22\. **Filesystem and Storage Management**

* `lsattr`: Lists attributes of files and directories.
    
    * Example: `lsattr file.txt`
        
* `chattr`: Changes file attributes, for example, to make a file immutable.
    
    * Example: `chattr +i file.txt`
        
* `xfs_admin`: Manages XFS file systems (resizing, repairing, etc.).
    
    * Example: `xfs_admin -L new_label /dev/sda1`
        
* `quota`: Displays disk quotas and user limits on filesystems.
    
    * Example: `quota -u username`
        
* `lvm`: Logical Volume Manager commands like `lvcreate`, `vgextend`, etc.
    
    * Example: `lvcreate -L 10G -n lv_data vg1`, `lvextend -L +5G /dev/vg1/lv_data`
        
* `cryptsetup`: Sets up encrypted filesystems using LUKS (Linux Unified Key Setup).
    
    * Example: `cryptsetup luksFormat /dev/sda1`, `cryptsetup luksOpen /dev/sda1 secure_drive`
        

### 23\. **Development and Debugging Tools**

* `gdb`: GNU Debugger, used for debugging programs.
    
    * Example: `gdb ./program`, `gdb --pid=<PID>`
        
* `objdump`: Displays detailed information about binary files.
    
    * Example: `objdump -d binary_file`
        
* `ldd`: Displays shared library dependencies for executable files.
    
    * Example: `ldd /bin/ls`
        
* `valgrind`: A tool for memory debugging, memory leak detection, and profiling.
    
    * Example: `valgrind ./program`
        
* `nm`: Displays symbols from object files.
    
    * Example: `nm a.out`
        
* `strace`: Tracks system calls and signals a process makes.
    
    * Example: `strace -p <PID>`
        

### 24\. **Package Management Tools**

* `dpkg`: Low-level package management for Debian-based distributions (like Ubuntu).
    
    * Example: `dpkg -i package.deb`, `dpkg -l` (list installed packages)
        
* `rpm`: Low-level package management for Red Hat-based distributions.
    
    * Example: `rpm -ivh package.rpm`, `rpm -qa` (list installed packages)
        
* `yum`: High-level package manager for Red Hat/CentOS (predecessor of `dnf`).
    
    * Example: `yum search package_name`, `yum remove package_name`
        
* `dnf`: Modern package manager for Red Hat/CentOS/Fedora.
    
    * Example: `dnf install package_name`, `dnf update`
        
* `snap`: Manages snap packages, often used for containerized applications.
    
    * Example: `snap install package_name`, `snap list`
        
* `flatpak`: Another framework for distributing desktop applications in containers.
    
    * Example: `flatpak install package_name`
        

### 25\. **Containers and Virtualization**

* `virsh`: CLI interface for managing virtual machines using libvirt.
    
    * Example: `virsh list --all`, `virsh start vm1`
        
* `kvm`: Manages kernel-based virtual machines.
    
    * Example: `kvm -hda disk.img -m 512 -net nic -net user`
        
* `docker-compose`: Manages multi-container Docker applications using YAML configuration files.
    
    * Example: `docker-compose up`, `docker-compose down`
        
* `podman`: A daemonless container engine that is compatible with Docker.
    
    * Example: `podman run -it fedora`, `podman ps`
        
* `lxc`: Linux Containers toolset, alternative to Docker for containerization.
    
    * Example: `lxc-create -n container -t download`, `lxc-start -n container`
        

### 26\. **Performance Monitoring**

* `perf`: Performance analysis tool for Linux, particularly useful for kernel developers.
    
    * Example: `perf top`, `perf record -a`
        
* `sar`: Collects and reports system activity information.
    
    * Example: `sar -u 1 3` (CPU utilization over 1-second intervals)
        
* `iotop`: Real-time disk I/O monitoring by process.
    
    * Example: `iotop`
        
* `latencytop`: Identifies latency issues in your system.
    
* `dstat`: A versatile resource monitoring tool that combines features of `vmstat`, `iostat`, and `netstat`.
    
    * Example: `dstat --cpu --io --net`
        

### 27\. **Security and Cryptography**

* `fail2ban`: Protects your server from brute-force attacks by blocking IP addresses.
    
    * Example: `sudo fail2ban-client status`, `sudo fail2ban-client set sshd banip <IP>`
        
* `gpg`: GNU Privacy Guard for encrypting and signing files or messages.
    
    * Example: `gpg --gen-key`, `gpg -e -r recipient file.txt`
        
* `openssl`: Toolset for SSL/TLS, certificates, and cryptography functions.
    
    * Example: `openssl genpkey -algorithm RSA -out private.pem`
        
* `nmap`: A powerful network scanning tool for security auditing and network exploration.
    
    * Example: `nmap -A 192.168.1.1`
        

### 28\. **Miscellaneous**

* `tldr`: Displays simplified and practical examples of common commands.
    
    * Example: `tldr tar`
        
* `bc`: A command-line calculator supporting floating-point arithmetic.
    
    * Example: `echo "scale=2; 10/3" | bc`
        
* `yes`: Continuously outputs a string until terminated.
    
    * Example: `yes "I agree"`
        
* `shuf`: Generates random permutations from input lines.
    
    * Example: `shuf -n 1 file.txt` (outputs a random line from a file)
        
* `units`: Converts between different units of measurement.
    
    * Example: `units '10 miles' 'kilometers'`
        
* `tree`: Displays a directory structure in a tree-like format.
    
    * Example: `tree /path/to/directory`
        
* `alias`: Defines a shortcut for a command.
    
    * Example: `alias ll='ls -la'`
        

### 30\. **Specialized File Management Commands**

* `split`: Splits a file into smaller chunks.
    
    * Example: `split -b 100M largefile.bin part_` (splits a file into 100 MB chunks)
        
* `shred`: Securely deletes a file by overwriting it multiple times.
    
    * Example: `shred -u file.txt`
        
* `rev`: Reverses the characters in each line of a file.
    
    * Example: `echo "hello" | rev` (outputs `olleh`)
        
* `rename`: Renames multiple files using a regular expression.
    
    * Example: `rename 's/\.txt$/.bak/' *.txt` (renames `.txt` files to `.bak`)
        
* `xxd`: Converts a file to hexadecimal and back.
    
    * Example: `xxd file.txt`, `xxd -r file.hex`
        

### 31\. **Advanced Scripting and Text Processing**

* `xargs`: Constructs argument lists and passes them to a command.
    
    * Example: `find . -name '*.txt' | xargs rm` (removes all `.txt` files)
        
* `tee`: Reads from standard input and writes to both standard output and a file.
    
    * Example: `echo "hello" | tee output.txt` (writes "hello" to both terminal and file)
        
* `paste`: Merges lines of files horizontally.
    
    * Example: `paste file1.txt file2.txt` (merges lines from both files side-by-side)
        
* `comm`: Compares two sorted files line by line.
    
    * Example: `comm file1.txt file2.txt`
        
* `tac`: Displays the contents of a file in reverse order (last line first).
    
    * Example: `tac file.txt`
        
* `expr`: Evaluates expressions (useful in shell scripts for arithmetic).
    
    * Example: `expr 1 + 2`
        
* `bc`: Command-line calculator.
    
    * Example: `echo "2^10" | bc`
        
* `tr`: Translates or deletes characters in input.
    
    * Example: `echo "HELLO" | tr 'A-Z' 'a-z'` (converts to lowercase)
        

### 32\. **Terminal Utilities and Shortcuts**

* `tmux`: Terminal multiplexer to manage multiple terminal sessions.
    
    * Example: `tmux` (starts a new session), `tmux attach` (reattaches to an existing session)
        
* `screen`: Another terminal multiplexer, similar to `tmux`.
    
    * Example: `screen` (starts a new session), `screen -r` (reattaches to a session)
        
* `reset`: Resets the terminal display and clears any weird states.
    
    * Example: `reset`
        
* `script`: Records a terminal session to a file.
    
    * Example: `script session.txt`
        
* `yes`: Repeats a string until terminated.
    
    * Example: `yes "agree"` (repeats "agree" until stopped with Ctrl+C)
        

### 33\. **System Monitoring and Information**

* `lsmod`: Lists loaded kernel modules.
    
    * Example: `lsmod`
        
* `uptime`: Displays system uptime and load averages.
    
    * Example: `uptime`
        
* `lshw`: Lists detailed hardware information.
    
    * Example: `sudo lshw`
        
* `inxi`: Displays detailed system information (including CPU, GPU, RAM, etc.).
    
    * Example: `inxi -Fx`
        
* `acpi`: Displays battery status and thermal information (useful for laptops).
    
    * Example: `acpi -b`
        
* `lsof`: Lists open files and processes using them.
    
    * Example: `lsof /dev/sda1`
        
* `dmesg`: Displays kernel-related messages (especially useful for debugging hardware issues).
    
    * Example: `dmesg | grep error`
        
* `vmstat`: Reports virtual memory, process, and CPU activity.
    
    * Example: `vmstat 5` (reports every 5 seconds)
        
* `watch`: Executes a command repeatedly and displays the output.
    
    * Example: `watch -n 2 df -h` (runs `df -h` every 2 seconds)
        

### 34\. **Networking and Connectivity Tools**

* `whois`: Queries domain registration information.
    
    * Example: `whois` [`google.com`](http://google.com/)
        
* `host`: Performs DNS lookups.
    
    * Example: `host` [`google.com`](http://google.com/)
        
* `iwconfig`: Configures wireless network interfaces (similar to `ifconfig` but for wireless).
    
    * Example: `iwconfig wlan0`
        
* `w`: Displays who is logged into the system and their activities.
    
    * Example: `w`
        
* `ip addr`: Shows detailed network interface information (replacement for `ifconfig`).
    
    * Example: `ip addr show`
        
* `ip route`: Manages routing tables.
    
    * Example: `ip route add 192.168.1.0/24 via 192.168.0.1`
        

### 35\. **Process and System Control**

* `pkill`: Sends a signal to a process by its name (alternative to `kill`).
    
    * Example: `pkill firefox`
        
* `renice`: Alters the scheduling priority of a running process.
    
    * Example: `renice +5 -p <PID>`
        
* `fg`: Brings a background process to the foreground.
    
    * Example: `fg %1` (brings job 1 to the foreground)
        
* `bg`: Resumes a suspended job in the background.
    
    * Example: `bg %1` (resumes job 1 in the background)
        

### 36\. **User and Group Management**

* `groups`: Shows the groups a user is part of.
    
    * Example: `groups username`
        
* `useradd`: Adds a new user.
    
    * Example: `sudo useradd -m username`
        
* `usermod`: Modifies a user account.
    
    * Example: `usermod -aG sudo username`
        
* `passwd`: Changes a user's password.
    
    * Example: `passwd username`
        
* `chage`: Changes user password expiration information.
    
    * Example: `sudo chage -l username`
        

### 37\. **System Maintenance and Troubleshooting**

* `fsck`: Checks and repairs file system inconsistencies.
    
    * Example: `fsck /dev/sda1`
        
* `badblocks`: Searches for bad sectors on a disk.
    
    * Example: `sudo badblocks -v /dev/sda1`
        
* `smartctl`: Monitors the health of hard drives and SSDs via S.M.A.R.T.
    
    * Example: `sudo smartctl -a /dev/sda`
        
* `iotop`: Displays disk I/O usage by processes in real time.
    
    * Example: `iotop`
        

### 38\. **Archiving and Compression**

* `tar`: Archive files into a tarball or extract files.
    
    * Example: `tar -czvf archive.tar.gz folder/`, `tar -xvzf archive.tar.gz`
        
* `gzip`: Compresses or decompresses files.
    
    * Example: `gzip file.txt`, `gunzip file.txt.gz`
        
* `bzip2`: Compresses files using the Burrows-Wheeler block-sorting text compression algorithm.
    
    * Example: `bzip2 file.txt`
        
* `xz`: Compresses files with higher compression than `gzip` or `bzip2`.
    
    * Example: `xz file.txt`
        
* `unzip`: Extracts files from a ZIP archive.
    
    * Example: `unzip` [`archive.zip`](http://archive.zip/)
        

### 39\. **Date and Time**

* `date`: Displays or sets the system date and time.
    
    * Example: `date`, `date --set="2024-10-11 10:30"`
        
* `cal`: Displays a calendar.
    
    * Example: `cal`
        
* `ntpq`: Monitors NTP daemon and shows the status of time synchronization.
    
    * Example: `ntpq -p`
        

### 40\. **Miscellaneous Useful Commands**

* `flock`: Manages file locking in shell scripts.
    
    * Example: `flock /tmp/mylockfile command`
        
* `chroot`: Changes the root directory for a process (used for system recovery and containers).
    
    * Example: `chroot /mnt/recovery /bin/bash`
        
* `ncdu`: Disk usage analyzer with a text-based user interface (faster alternative to `du`).
    
    * Example: `ncdu /home`
        
* `hexdump`: Displays file contents in hexadecimal, decimal
    
* `uptime`: Displays system uptime, load averages, and number of users logged in.
    
    * Example: `uptime`
        
* `alias`: Creates a shortcut for a command.
    
    * Example: `alias ll='ls -la'`
        
* `bc`: A command-line calculator.
    
    * Example: `echo "5 * 7" | bc`
        
* `env`: Displays environment variables.
    
    * Example: `env`