Linux Network Administration Cheat Sheet

Basic Networking Commands

ifconfig            # Display or configure network interfaces
ip addr show        # Show IP addresses
ip link show        # Show link layer information
ip route show       # Display the routing table
ping host           # Send ICMP ECHO_REQUEST to network hosts
traceroute host     # Print the route packets take to the network host
netstat -tuln       # List all listening ports
ss -tuln            # List all listening ports using the socket statistics command
arp -a              # Display the ARP table
hostname            # Show or set the system's hostname

Use Cases

ifconfig: Used to check network interface configurations and troubleshoot network connectivity issues.

ping: Used to check the connectivity between the local system and a remote host.

traceroute: Useful for diagnosing network routing issues by showing the path packets take to reach a host.

netstat and ss: Useful for monitoring network connections and identifying open ports on the system.

Network Configuration

nmtui               # Text user interface for network management
nmcli dev status    # Show device status
nmcli con show      # Show available connections
nmcli con up id "name" # Bring up the specified connection
nmcli con down id "name" # Bring down the specified connection
systemctl restart NetworkManager # Restart the NetworkManager service
/etc/network/interfaces # Network configuration file (Debian/Ubuntu)
cat /etc/resolv.conf # Show DNS servers
resolvectl status   # Show resolver information

Use Cases

nmtui: A user-friendly interface for managing network connections, ideal for users who prefer a graphical interface over command-line.

nmcli: Command-line tool for managing network connections, useful for scripting and automation.

systemctl restart NetworkManager: Useful for applying new network configurations or troubleshooting network issues by restarting the NetworkManager service.

Network Diagnostics

ping -c 4 host      # Ping host with 4 packets
traceroute host     # Trace the path to a host
mtr host            # Network diagnostic tool combining ping and traceroute
dig domain          # DNS lookup
nslookup domain     # Query Internet name servers interactively
whois domain        # Get whois information for a domain
ethtool eth0        # Display or change Ethernet device settings
tcpdump -i eth0     # Dump traffic on interface eth0

Use Cases

mtr: Provides real-time network diagnostic information, useful for identifying network bottlenecks and packet loss.

dig and nslookup: Useful for DNS troubleshooting by querying DNS records for a domain.

ethtool: Provides detailed information about network interfaces and allows for configuration changes, such as enabling/disabling autonegotiation or changing speed settings.

tcpdump: Captures network packets for analysis, useful for troubleshooting complex network issues and security monitoring.

Firewall Management

ufw status          # Check the status of UFW (Uncomplicated Firewall)
ufw enable          # Enable UFW
ufw disable         # Disable UFW
ufw allow port      # Allow traffic on the specified port
ufw deny port       # Deny traffic on the specified port
iptables -L         # List current iptables rules
iptables -A INPUT -p tcp --dport 22 -j ACCEPT # Allow SSH connections
iptables -A INPUT -j DROP # Drop all other incoming traffic

Use Cases

ufw: Simplifies firewall management, making it easier to allow or deny traffic on specific ports without complex rules.

iptables: Provides detailed control over the firewall rules and network traffic filtering, useful for advanced network security configurations.

Remote Access and Monitoring

ssh user@remote_host        # Connect to a remote host via SSH
scp file user@remote_host:/path # Copy file to remote host via SCP
rsync -avz file user@remote_host:/path # Sync files with a remote host via rsync
ssh-keygen                 # Generate SSH keys
ssh-copy-id user@remote_host # Copy SSH key to remote host
tmux                       # Terminal multiplexer for managing multiple sessions
screen                     # Screen manager with VT100/ANSI terminal emulation
top                        # Display dynamic real-time information about running processes
htop                       # Interactive process viewer
nload                      # Monitor network traffic and bandwidth usage
iftop                      # Display bandwidth usage on an interface by host
vnstat                     # Network traffic monitor

Use Cases

ssh: Provides secure remote login capabilities, essential for managing remote servers.

scp and rsync: Useful for securely transferring files between local and remote systems, with rsync providing advanced synchronization options.

tmux and screen: Allows for managing multiple terminal sessions, useful for long-running processes and remote work.

htop: An interactive process viewer that provides an easy-to-read and user-friendly interface for monitoring system resources.

nload and iftop: Real-time network traffic monitoring tools, useful for analyzing bandwidth usage and identifying traffic patterns.

Network Services Management

systemctl start service    # Start a network service
systemctl stop service     # Stop a network service
systemctl restart service  # Restart a network service
systemctl status service   # Check the status of a network service
journalctl -u service      # View logs for a specific service
chkconfig --list           # List all available services (Red Hat-based)
update-rc.d service defaults # Set defaults for a service (Debian-based)

Use Cases

systemctl: Manages systemd services, allowing administrators to start, stop, restart, and check the status of services, which is essential for managing network services like web servers, databases, and firewalls.

journalctl: Provides access to system logs, which is useful for troubleshooting service-related issues.

Miscellaneous Networking Tools

wget URL                   # Download files from the web
curl URL                   # Transfer data from or to a server
ftp host                   # FTP client
sftp user@remote_host      # Secure FTP client
nmap host                  # Network exploration tool and security/port scanner
wireshark                  # Network protocol analyzer