eth0

eth0 is the conventional name for the first Ethernet network interface on Linux and many Unix-like systems. Historically the kernel assigned eth0 to the first detected Ethernet device; with the advent of udev and predictable naming, names like enp0s3 or ens33 are common, but eth0 remains widely used as a compatibility alias or in older scripts.

The interface corresponds to a network device driver and is represented in /sys/class/net/eth0; it may be a physical card, a virtual NIC in a VM, or a container bridge. The interface can carry IPv4 and IPv6 addresses, learned via DHCP or configured statically. Common management tasks use the ip command (preferred) or, in older systems, ifconfig. For example, to view the status: ip addr show eth0; to bring the interface up: ip link set eth0 up; to assign an address: ip addr add 192.0.2.10/24 dev eth0.

Configuration across distributions varies. Debian and Ubuntu historically used /etc/network/interfaces; Red Hat and derivatives used ifcfg-eth0; modern systems typically rely on NetworkManager or netplan, which can configure eth0 via GUI tools or YAML definitions. In many servers, DHCP is used to obtain an address automatically, while servers may use static addressing for predictable routing.

In virtual environments, eth0 commonly represents the first virtual NIC connected to a virtual switch. Because modern Linux systems may name interfaces predictably, eth0 can be a symlink or absent; administrators may choose to preserve legacy naming with udev rules or kernel parameters if required.