Debian Commands Guide — Essential Reference

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📦 Package Management (apt / dpkg)

Debian uses the Advanced Package Tool (apt) and dpkg for managing software packages. These are the most essential commands every Debian user should know.

Basic apt Commands

Command	Description
`sudo apt update`	Update package lists from repositories
`sudo apt upgrade`	Upgrade all installed packages to latest versions
`sudo apt full-upgrade`	Upgrade packages, handling dependency changes (may remove packages)
`sudo apt install <package>`	Install a new package
`sudo apt remove <package>`	Remove a package (keeps config files)
`sudo apt purge <package>`	Remove a package and its configuration files
`sudo apt autoremove`	Remove unused dependency packages
`sudo apt autoclean`	Clean up old package files from the cache
`apt search <term>`	Search for packages by name or description
`apt show <package>`	Show detailed information about a package
`apt list --installed`	List all installed packages
`apt list --upgradable`	List packages that can be upgraded
`apt policy <package>`	Show version policy and repository priority

bash

# Full system update routine
$ sudo apt update
$ sudo apt full-upgrade -y
$ sudo apt autoremove --purge -y
$ sudo apt autoclean
                    

dpkg Commands

Command	Description
`dpkg -i <file.deb>`	Install a .deb package file
`dpkg -r <package>`	Remove a package
`dpkg -P <package>`	Purge a package (remove + configs)
`dpkg -l`	List all installed packages
`dpkg -l \| grep <term>`	Search installed packages
`dpkg -s <package>`	Show package status and info
`dpkg -L <package>`	List files installed by a package
`dpkg -S <file>`	Find which package owns a file
`dpkg --configure -a`	Fix broken package configurations

⚠️

apt vs dpkg

Always prefer apt over dpkg for installing packages, as apt automatically resolves dependencies. Use dpkg for installing local .deb files and querying package information.

⚙️ System Administration

System Information

Command	Description
`uname -a`	Display kernel and system information
`cat /etc/os-release`	Show OS version and codename
`hostnamectl`	Display and control system hostname
`lsb_release -a`	Show LSB and distribution information
`inxi -Fxz`	Detailed hardware and system info (install with apt)
`neofetch`	Pretty system information display (install with apt)
`uptime`	Show how long the system has been running
`whoami`	Display current username
`date`	Display current date and time

Systemd Service Management

bash

# Start a service
$ sudo systemctl start nginx

# Stop a service
$ sudo systemctl stop nginx

# Restart a service
$ sudo systemctl restart nginx

# Enable service to start at boot
$ sudo systemctl enable nginx

# Disable service from starting at boot
$ sudo systemctl disable nginx

# Check service status
$ systemctl status nginx

# List all running services
$ systemctl list-units --type=service --state=running

# View system logs
$ journalctl -xe

# View logs for a specific service
$ journalctl -u nginx -f
                    

Boot & Shutdown

Command	Description
`sudo shutdown -h now`	Shut down the system immediately
`sudo shutdown -r now`	Reboot the system immediately
`sudo shutdown -h +30`	Shut down in 30 minutes
`sudo reboot`	Reboot the system
`sudo poweroff`	Power off the system

📁 Files & Disk Management

File Operations

Command	Description
`ls -la`	List all files with details (hidden included)
`cd /path`	Change directory
`mkdir -p dir1/dir2/dir3`	Create directories (including parents)
`cp -r src/ dest/`	Copy directory recursively
`mv file1 file2`	Move or rename a file
`rm -rf directory/`	Remove directory recursively (⚠️ dangerous)
`find / -name "file.txt"`	Search for files by name
`locate file.txt`	Quick file search (uses updatedb database)
`cat file.txt`	Display file contents
`less file.txt`	View file contents page by page
`head -n 20 file.txt`	Show first 20 lines of a file
`tail -f /var/log/syslog`	Follow log file in real-time
`grep "pattern" file.txt`	Search for text pattern in file
`grep -r "pattern" /path/`	Recursively search for pattern in directory
`wc -l file.txt`	Count lines in a file
`diff file1 file2`	Compare two files

Disk & Storage

bash

# Check disk space usage
$ df -h

# Check directory sizes
$ du -sh /*

# Find large files (over 100MB)
$ find / -type f -size +100M

# List block devices
$ lsblk

# Check file system type
$ sudo blkid

# Check inode usage
$ df -i
                    

🌐 Network Commands

Command	Description
`ip addr show`	Show IP addresses on all interfaces
`ip link show`	Show network interfaces
`ip route show`	Show routing table
`ip link set eth0 up`	Enable network interface
`ping -c 4 debian.org`	Ping a host 4 times
`curl -s ifconfig.me`	Get public IP address
`dig debian.org`	Query DNS records
`nslookup debian.org`	Lookup DNS information
`ss -tuln`	Show listening ports (modern netstat replacement)
`ss -s`	Show socket statistics summary
`traceroute debian.org`	Trace network route to host
`wget https://url/file`	Download a file from the web
`curl -O https://url/file`	Download a file preserving name

Firewall (UFW)

bash

# Install UFW (if not installed)
$ sudo apt install ufw

# Enable firewall
$ sudo ufw enable

# Check status
$ sudo ufw status verbose

# Allow SSH
$ sudo ufw allow 22/tcp

# Allow HTTP and HTTPS
$ sudo ufw allow 80/tcp
$ sudo ufw allow 443/tcp

# Deny a specific IP
$ sudo ufw deny from 192.168.1.100

# Delete a rule
$ sudo ufw delete allow 80
                    

👤 Users, Permissions & Processes

User Management

Command	Description
`sudo adduser username`	Create a new user (interactive)
`sudo deluser username`	Delete a user
`sudo usermod -aG sudo username`	Add user to sudo group
`sudo passwd username`	Change user password
`id username`	Show user ID and groups
`groups username`	Show groups a user belongs to
`who`	Show logged-in users
`last`	Show login history

File Permissions

bash

# Change permissions (read=4, write=2, execute=1)
$ chmod 755 script.sh      # rwxr-xr-x
$ chmod 644 file.txt     # rw-r--r--
$ chmod 600 secret.key   # rw-------

# Change ownership
$ sudo chown user:group file

# Change ownership recursively
$ sudo chown -R user:group directory/
                    

Process Management

Command	Description
`ps aux`	List all running processes
`top`	Interactive process viewer
`htop`	Enhanced interactive process viewer (install with apt)
`kill PID`	Send SIGTERM to a process
`kill -9 PID`	Force kill a process (SIGKILL)
`pkill processname`	Kill process by name
`pgrep processname`	Find PID by process name
`lsof -i :80`	Show which process uses port 80
`free -h`	Show memory usage in human-readable format
`vmstat 1`	Virtual memory statistics (update every 1s)

🔧 Shell & Text Processing

bash

# Text processing with grep
$ grep -i "error" /var/log/syslog          # Case-insensitive search
$ grep -r "TODO" /home/user/project/    # Recursive search
$ grep -c "pattern" file                 # Count matching lines

# Text processing with sed
$ sed -i s/old/new/g file.txt             # Find and replace in-place
$ sed -n '5,10p' file.txt                  # Print lines 5-10

# Text processing with awk
$ awk '{print $1}' file.txt               # Print first column
$ awk '-F:' '{print $1}' /etc/passwd      # Print usernames from passwd

# Compression
$ tar -czf archive.tar.gz directory/      # Create gzip archive
$ tar -xzf archive.tar.gz                  # Extract gzip archive
$ tar -tjf archive.tar.bz2                 # List bzip2 archive contents

# Pipes and redirection
$ cat file | grep "pattern" | sort | uniq
$ command > output.txt                     # Redirect output to file
$ command 2>&1 > log.txt                    # Redirect stdout and stderr
                    