How to Configure a Static IP Address in Linux? (Configuration File Example)

To configure Linux static IP, you need to choose the corresponding method according to the release version: Debian/Ubuntu uses /etc/network/interfaces, RHEL/CentOS uses /etc/sysconfig/network-scripts/ifcfg-, and systemd system can use /etc/systemd/network/.network; after editing, restart the corresponding network service and verify.

To configure a static IP address in Linux, you typically edit the network interface configuration file — location and format depend on your distribution and init system. The most common and widely supported method is using /etc/network/interfaces (Debian/Ubuntu with ifupdown) or /etc/sysconfig/network-scripts/ifcfg-* (RHEL/CentOS/Fedora with NetworkManager or legacy network service). Systemd-based systems may also use .network files in /etc/systemd/network/ .

Debian/Ubuntu (ifupdown – /etc/network/interfaces)

This method works on older Debian-based systems or those still using ifupdown. Replace eth0 with your actual interface name (eg, ens33 , enp0s3 ).

Example:

 # /etc/network/interfaces
autoeth0
iface eth0 inet static
    address 192.168.1.100
    netmask 255.255.255.0
    gateway 192.168.1.1
    dns-nameservers 8.8.8.8 1.1.1.1
    dns-search example.com

Apply changes with:

• sudo ifdown eth0 && sudo ifup eth0 — to restart just that interface
• sudo systemctl restart networking — for full service reload (if networking service is enabled)

RHEL/CentOS/Fedora (ifcfg files)

Look for /etc/sysconfig/network-scripts/ifcfg-eth0 (or similar). Edit it to disable DHCP and set static values.

Example:

 # /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
IPADDR=192.168.1.100
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=8.8.8.8
DNS2=1.1.1.1
SEARCH=example.com

Restart networking with:

• sudo ifdown eth0 && sudo ifup eth0
• Or on modern RHEL/CentOS 8 , use sudo nmcli connection reload && sudo nmcli connection down "System eth0" && sudo nmcli connection up "System eth0"

systemd-networkd (modern minimal systems)

Used on lightweight or container-optimized distros (eg, Arch, Fedora CoreOS, Ubuntu Server 20.04 optionally). Files go in /etc/systemd/network/ .

Example:

 # /etc/systemd/network/20-static-eth0.network
[Match]
Name=eth0
<p>[Network]
Address=192.168.1.100/24
Gateway=192.168.1.1
DNS=8.8.8.8
DNS=1.1.1.1

Enable and apply:

• sudo systemctl enable systemd-networkd
• sudo systemctl restart systemd-networkd
• sudo systemctl restart systemd-resolved (if using resolved for DNS)

Verify & troubleshoot

After applying settings:

• Check IP: ip addr show eth0 or ip a
• Test routing: ip route
• Test DNS: nslookup google.com or dig google.com
• Confirm gateway reachability: ping -c 3 192.168.1.1
• Double-check interface name with ip link — many systems now use predictable names like ens33 instead of eth0

Basically, pick the method matching your distro and init system — then double-check the interface name and restart the right service. It's not complex, but easy to overlook a typo or mismatched service command.

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