Network Configuration Files Explained

Key Concepts

• /etc/hosts
• /etc/hostname
• /etc/resolv.conf
• /etc/network/interfaces
• /etc/sysconfig/network
• /etc/nsswitch.conf

/etc/hosts

The /etc/hosts file maps hostnames to IP addresses. It is used to resolve hostnames to IP addresses locally, bypassing DNS. This file is useful for defining custom hostnames and IP addresses for local or internal networks.

Example: Adding a line "192.168.1.100 myserver" to /etc/hosts allows you to access the server with the hostname "myserver" instead of its IP address.

/etc/hostname

The /etc/hostname file contains the hostname of the system. This file is read during system boot to set the hostname. The hostname is a unique identifier for the system on the network.

Example: Setting the hostname to "linuxbox" by editing /etc/hostname will make the system identifiable as "linuxbox" on the network.

/etc/resolv.conf

The /etc/resolv.conf file contains DNS resolver configuration. It specifies the DNS servers to be used for hostname resolution. This file is crucial for resolving domain names to IP addresses.

Example: Adding "nameserver 8.8.8.8" to /etc/resolv.conf configures the system to use Google's public DNS server for hostname resolution.

/etc/network/interfaces

The /etc/network/interfaces file is used to configure network interfaces in Debian-based systems. It defines how network interfaces should be configured, including IP addresses, gateways, and DNS settings.

Example: Configuring the interface "eth0" with a static IP address by adding lines to /etc/network/interfaces: "iface eth0 inet static\naddress 192.168.1.10\nnetmask 255.255.255.0\ngateway 192.168.1.1".

/etc/sysconfig/network

The /etc/sysconfig/network file contains network configuration settings for Red Hat-based systems. It includes settings like the hostname and whether networking should be enabled.

Example: Setting the hostname to "redhatserver" by editing /etc/sysconfig/network: "HOSTNAME=redhatserver".

/etc/nsswitch.conf

The /etc/nsswitch.conf file controls the order in which different sources are consulted for name service lookups. It specifies the sources for resolving hostnames, user accounts, and other information.

Example: Configuring the order of hostname resolution by editing /etc/nsswitch.conf: "hosts: files dns" means the system will first check the /etc/hosts file and then query DNS.