Ubuntu/Apt

Network Commands

Configure networking and firewall rules on Ubuntu. Manage interfaces with Netplan, control access with UFW, troubleshoot connectivity, and configure DNS.

10 commands

Pro Tips

Use 'ufw allow 22/tcp' then 'ufw enable' — always allow SSH before enabling the firewall!

Use 'ss -tlnp' to see all listening ports and which processes own them — replaces 'netstat'.

Apply Netplan changes with 'sudo netplan try' — auto-reverts in 120 seconds if you lose connectivity.

Common Mistakes

Enabling UFW without allowing SSH first will lock you out of a remote server. Always 'ufw allow ssh' first.

Netplan config errors can break networking. Use 'netplan try' instead of 'netplan apply' on remote servers.

Commands

Apply netplan config

$ sudo netplan apply

Apply network configuration from /etc/netplan/*.yaml files.

Show IP addresses

$ ip addr show

Display all network interfaces and their IP addresses.

Enable UFW firewall

$ sudo ufw enable

Enable the Uncomplicated Firewall.

Allow port through UFW

$ sudo ufw allow <port>/tcp

Allow incoming TCP traffic on a specific port.

Deny port through UFW

$ sudo ufw deny <port>

Block incoming traffic on a specific port.

Show UFW status

$ sudo ufw status verbose

Display firewall rules and current status with details.

Delete UFW rule

$ sudo ufw delete allow <port>/tcp

Remove a previously added firewall rule.

Test netplan config

$ sudo netplan try

Test netplan configuration with automatic rollback on failure.

Show hostname info

$ hostnamectl

Display the current hostname, OS, and architecture details.

Restart networking

$ sudo systemctl restart NetworkManager

Restart the NetworkManager service to apply network changes.