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⚙️ Editing Network Configuration Files

Editing Network Configuration Files

When you want to change your network settings permanently—like IP address, DNS, or gateway—you edit configuration files. This is deeper than just running ifconfig or ip a, which are temporary changes.

Locations of Config Files

The location depends on your Linux distribution:

1. Debian/Ubuntu:

  • Main file: /etc/network/interfaces (older systems)
  • Or /etc/netplan/*.yaml (modern Ubuntu versions)

2. RedHat/CentOS/Fedora:

  • Main files: /etc/sysconfig/network-scripts/ifcfg-<interface>
  • Example: /etc/sysconfig/network-scripts/ifcfg-eth0

3. DNS settings:

  • /etc/resolv.conf → contains DNS server addresses

Editing the Files

1. Debian/Ubuntu (Netplan example):

📌 Example: 
network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      addresses: [192.168.1.50/24]
      gateway4: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

Apply changes:

sudo netplan apply

2. RedHat/CentOS (ifcfg example):

📌 Example: 
DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
IPADDR=192.168.1.50
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=8.8.8.8
DNS2=8.8.4.4

Restart network service to apply:

sudo systemctl restart network

Important Notes

Always backup the original file before editing:

sudo cp /etc/netplan/01-netcfg.yaml /etc/netplan/01-netcfg.yaml.bak

Small syntax mistakes can break network connectivity, so double-check formatting (especially YAML indentation). After changes, always test connectivity (ping, ip a) to confirm.

Real-life analogy

Think of these files as the "blueprints" of your house's network — who lives where, which door connects to which street, and which mailbox (DNS) to use. Editing config files is like rewiring your house — if done wrong, doors may not open, or mail won't arrive. But done correctly, your house is fully optimized for the neighborhood.

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