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Linux Setup: Hostname and Static IP

Note

This page contains {{ jinja2_style_variable_syntax }} in example commands or configs. Replace them with the appropriate values when using the code or values in question.

Set Hostname

Systemd-based distros

run hostnamectl set-hostname {{ new_hostname }}

Any currently logged-in users will need to log out and log back in to see the new hostname reflected.

Generic method

replace the old hostname in /etc/hosts and /etc/hostname.

Configure Static IP

Used on Ubuntu Desktop and CentOS 8, among others

CentOS 7

  1. Run ip link show, and note the interface you are going to change. (In my case, it's ens192).

  2. Edit the file /etc/sysconfig/network-scripts/ifcfg-{{ IFNAME }} to edit or add the following values:

BOOTPROTO=none
ONBOOT=yes
IPADDR={{ IP_ADDR }}
PREFIX={{ PREFIX }}
GATEWAY={{ GATEWAY }}
DNS1={{ DNS_IP }}
  • {{ IFNAME }}: name of the interface
  • {{ IP_ADDR }}: the IP address
  • {{ PREFIX }}: number of bits in the subnet mask
  • {{ GATEWAY }}: the default gateway
  • {{ DNS_IP }}: the IP address of the default gateway

Additionally, to specify a Search Domain, add the line DOMAIN={{ SEARCH_DOMAIN_0 }}

As a more concrete example, if you were setting up a static IP of 192.0.2.131 on the network 192.0.2.0/25, with a default gateway of 192.0.2.129, and a DNS server at 192.0.2.130, and the search domain for.example, you would want to use the following values: 

BOOTPROTO=none
ONBOOT=yes
IPADDR=192.0.2.131
PREFIX=25
GATEWAY=192.0.2.129
DNS1=192.0.2.131
DOMAIN=for.example
2. Restart the network service with systemctl restart network.

Ubuntu Netplan

Starting with Ubuntu 18.04, networking can be configured with netplan, which will automatically configure networking based on the contents of a YAML file using either NetworkManager or Systemd-networkd.

  1. escalate to root: sudo -i

  2. get a list of network interfaces: ip link show

    • from this point on, I'll be using the interface enp3s0 for ethernet and wlp2s0 for wi-fi. If working with a different interface, replace any reference to either of them with the appropriate interface.

  3. create a new YAML file in /etc/netplan/.

    • For the sake of these notes, I'm naming mine 02-static-ensp3s0.yaml, but any file ending in .yaml should work. It's best to start with a number, so that it's clear which are prioritised (02-static-ensp3s0.yaml would override any contradictory settings in an existing file called 01-old-configuration.yaml)

  4. using a text editor (e.g. vim, nano, or gedit), add the following to the YAML file you created, replacing {{ jinja2_style_placeholders }} with the appropriate values:

FOR ETHERNET CONNECTIONS:

network:
  version: 2
  renderer: "{{ RENDERER }}"
  ethernets:
    enp3s0:
      dhcp4: false
      dhcp6: false
      addresses:
        - "{{ IP_ADDRESS }}/{{ PREFIX }}"
      #gateway4: "{{ GATEWAY }}"
      routes:
        - to: default
        - via: "{{ GATEWAY }}"
      nameservers:
        search: ["{{ SEARCH }}"]
        addresses: ["{{ DNS_IP }}"]

FOR WIFI NETWORKS:

network:
  version: 2
  renderer: "{{ RENDERER }}"
  wifis:
    wlp2s0:
      dhcp4: no
      dhcp6: no
      addresses:
        - "{{ IP_ADDRESS }}/{{ PREFIX }}"
      #gateway4: "{{ GATEWAY }}"
      routes:
        - to: default
        - via: "{{ GATEWAY }}"
      nameservers:
        search: ["{{ SEARCH }}"]
        addresses: ["{{ DNS_IP }}"]
      access-points:
        "{{ SSID }}":
          password: "{{ WPA2_PASS }}"
  • {{ RENDERER }}: networkd or NetworkManager, depending on which you use.
    • NetworkManager is the default on Ubuntu Desktop, and systemd-networkd is the default for Ubuntu Server
  • {{ IP_ADDRESS }}: the IP address of the server
  • {{ PREFIX }}: the number of bits in the subnet mask
  • {{ GATEWAY }}: the default gateway
  • {{ SEARCH }}: search domains
  • {{ DNS_IP }}: ip address/es of DNS Server/s
    • if you have multiple search domains or DNS servers,separate them with a comma followed by a space
  • {{ SSID }}: the SSID (display name) of the network
  • {{ WPA2_PASS }}: The WPA2 password for the network

NOTE: as of Ubuntu 22.04 Jammy Jellyfish, gateway4 has been deprecated, and must be replaced with the routes: section. If working with an older version, either gateway4 or a routes: section with a default route will work, but I'd recommend sticking with the routes: section, as it will make any future upgrades smoother.

  1. test the configuration file with netplan try
  • this will attempt to use your settings, and revert to a previous configuration if they don't work.

  1. apply the netplan configuration: netplan apply

  2. restart the network

    • if using NetworkManager: systemctl restart NetworkManager
    • if using systemd-network: systemctl restart systemd-networkd

NetworkManager with nmcli

If on Ubuntu, this assumes that netplan is set up to delegate control to NetworkManager, which is the default on Ubuntu Desktop, but not Ubuntu Server. If on Ubuntu Server, I'd recommend sticking with netplan/systemd-networkd

  1. get a list of connections with nmcli con show

    • you can run nmcli con show --active to only display active connections

  2. edit the active connection with the following command (replacing {{ jinja2_style_placeholders }} as needed)

nmcli con mod "{{ CONNECTION }}" \
    ipv4.addresses "{{ IP_ADDRESS }}/{{ PREFIX }}" \
    ipv4.gateway "{{ DEFAULT_GATEWAY }}" \
    ipv4.dns "{{ DNS_IP_ADDRESS_0,DNS_IP_ADDRESS_1... }}" \
    ipv4.dns-search "{{ SEARCH_DOMAIN_0,SEARCH_DOMAIN_1... }}" \
    ipv4.method "manual"
  1. restart the connection: nmcli con down {{ CONNECTION }} && nmcli con up {{ CONNECTION }}