Linux Basics
Network and host configuration on Ubuntu. For everyday commands see Linux.
Change Hostname #
sudo hostnamectl set-hostname newhostnameAlso update the 127.0.1.1 line in /etc/hosts. Show the result with hostnamectl.
Netplan Basics #
Netplan reads YAML from /etc/netplan/*.yaml and drives systemd-networkd or NetworkManager.
| COMMAND | DESCRIPTION |
|---|---|
ip -br a | Find the interface name (e.g. ens3, eth0) |
sudo netplan try | Apply with automatic rollback after 120 s if you lose connectivity |
sudo netplan apply | Apply the configuration |
sudo netplan get | Show the merged config |
sudo netplan generate | Validate and generate backend config |
sudo chmod 600 /etc/netplan/*.yaml | Netplan warns if files are world-readable |
Change IP Address in Ubuntu 20.04 LTS #
- Create a new file
/etc/netplan/01-netcfg.yaml
network:
version: 2
renderer: networkd
ethernets:
ens3:
dhcp4: no
addresses:
- 192.168.121.221/24
gateway4: 192.168.121.1
nameservers:
addresses: [8.8.8.8, 1.1.1.1]- Apply changes
sudo netplan applyChange IP Address in Ubuntu 22.04 LTS and later #
gateway4 was deprecated in Ubuntu 22.04 and routes is used instead #
- Create a new file
/etc/netplan/01-netcfg.yaml
network:
version: 2
renderer: networkd
ethernets:
ens3:
dhcp4: no
addresses:
- 192.168.121.221/24
routes:
- to: default
via: 192.168.121.1
nameservers:
addresses: [8.8.8.8, 1.1.1.1]- Apply changes
sudo netplan applyDHCP #
network:
version: 2
ethernets:
ens3:
dhcp4: trueOther Basics #
| COMMAND | DESCRIPTION |
|---|---|
sudo timedatectl set-timezone Europe/London | Set the timezone |
timedatectl | Time, NTP and timezone status |
sudo timedatectl set-ntp true | Enable time sync |
sudo localectl set-locale LANG=en_GB.UTF-8 | Set the locale |
resolvectl status | DNS servers in use |
sudo ufw allow OpenSSH && sudo ufw enable | Basic firewall, see UFW (uncomplicated firewall) |
sudo apt update && sudo apt full-upgrade | Update the system |
sudo reboot / sudo poweroff | Reboot / shut down |
sudo unattended-upgrades --dry-run -d | Test automatic security updates |
sudo dpkg-reconfigure -plow unattended-upgrades | Enable automatic security updates |