Chapter 5. Networking

The netifrc configuration file consists of INI-style configuration variables. For example, config_eth0="dhcp" sets the variable config_eth0 to the value dhcp. By default, all interfaces on the system that are enabled will attempt to retrieve a DHCP address. Retrieving a DHCP address requires the dhcpcd package to be installed.

To enable a network interface, you must create a symbolic link to /etc/init.d/net.lo in /etc/init.d named net.IFACE where IFACE is the name of the interface. For example, for the interface named eth0, you would run ln -s /etc/init.d/net.lo /etc/init.d/net.eth0. Next, you need to add the service to the default runlevel. As noted in the section called “Enabling and disabling services”, you would run rc-update add net.IFACE default to enable the net.IFACE service. You may then start the service, assuming the interface has been configured properly in /etc/conf.d/net.

To disable a network interface, you must first stop it, if it is running. Next, remove it from the default runlevel (rc-update del net.IFACE default). Finally, remove the symbolic link in /etc/init.d.

Before we begin configuring the network, we will list the network adaptors available on your computer. This will ensure that the adaptor or adaptors were detected successfully by the kernel. To do this, ensure the iproute2 package is installed, and run the command ip link as root.

To explicitly configure an interface to use dynamic addressing via DHCP, set config_IFACE="dhcp", where IFACE is the interface you wish to use dynamic addressing. For more information on customising dynamic addressing, refer to the section called “Advanced: Customising dynamic addressing”.

The Adélie Linux system can be configured to provide bridged networking to a QEMU virtual machine or KVM guest using TAP networking. You will need the iproute2 package installed.

First, we will need to add a bridge to netifrc. A bridge allows multiple network adaptors to combine multiple network segments into a single aggregate. For our purposes, we will be combining the physical network adaptor on the host with the virtual network adaptors on each guest. The bridge will have your physical network adaptor as its first member. This way, no network reconfiguration will be required when you start or stop virtual machines. You will need to move the configuration for your physical network adaptor to the bridge, so that all members of the bridge may share that connection. In the following example, the interface eth0 is the physical adaptor and the bridge is set to use a static IPv6 address, which will then be used by the physical adaptor as well.

config_eth0="null"

bridge_br0="eth0"
config_br0="2001:db8::2/32"
routes_br0="default via 2001:db8::1"

Note that the physical adaptor must still be specified with a "null" configuration. This ensures that the link will still be activated and network traffic will still flow. If you are using DHCP, you may simply use config_br0="dhcp".

You will then need to replace your net.IFACE file with a net.br0 file in /etc/init.d. For example:

computer ~ # rc-update del net.eth0
computer ~ # service net.eth0 stop
computer ~ # mv /etc/init.d/net.eth0 /etc/init.d/net.br0
computer ~ # rc-update add net.br0 default
computer ~ # service net.br0 start

	Warning
	You will momentarily lose network connectivity after stopping net.IFACE. Do not perform these steps while connected to the machine over the network.

Now we need to create scripts for QEMU (or KVM) to use. The /etc/qemu-ifup script should be created as follows:

#!/bin/sh
ip tuntap add mode tap name $1
ip link set dev $1 master br0
ifconfig $1 up

The /etc/qemu-ifdown script should be created as follows:

#!/bin/sh
ifconfig $1 down
ip tuntap del name $1

You may now start your QEMU or KVM virtual machines with network access by adding -net tap to the command line. Note that if you have more than one guest that needs network access, you will need to set a custom MAC address for each NIC. Otherwise there will be MAC collisions and networking may not work correctly. For example:

This will start a machine with network access and a MAC address of 02:00:00:00:00:01.

Note that by default, all interfaces must be active before the rest of the system will consider the network to be active. This will cause network services to delay start-up until all interfaces are active. If this is not desired, you may set rc_depend_strict to NO in /etc/rc.conf.

You may use the dhcp_IFACE variable to control how DHCP is used. Valid options include: