Configure Networking

From Alpine Linux
Revision as of 08:51, 21 March 2025 by Prabuanand (talk | contribs) (moved ifupdown-ng configuration to its own heading)

This page documents various networking options available in Alpine Linux and helps to configure your network using either Network setup-scripts or manually and to test your Internet access.

The ifupdown-ng package installed as part of alpine-base provides necessary tools for managing network configuration. For additional tools refer NetworkManager. For WiFi, the default wireless daemon wpa_supplicant can be configured quickly by setup-interfaces script, but iwd is also fully supported in Alpine Linux.

Network setup-scripts

The following network related scripts are available from the alpine-conf package as part of Alpine setup scripts.

All the above utilities are interactive. When installing Alpine linux, the setup-alpine script should have given you the option to setup ethernet/networking. To setup networking quickly after installation use setup-interfaces script. The script configures wireless and ethernet interfaces in addition to other types and will satisfy most trivial configurations.

setup-interfaces

Start the script by running this command:

# setup-interfaces

Available interfaces are: eth0 wlan0.
Enter '?' for help on bridges, bonding and vlans.
Which one do you want to initialize? (or '?' or 'done') [eth0]

choose eth0 for Ethernet or wlan0 for wireless device, as appropriate.

if asked: 

Ip address for eth0? (or 'dhcp', 'none', '?') [dhcp]

choose dhcp, if you are using dhcp.

Now it will ask Do you to do any manual network configuration? (y/n) [n]

In most cases, you can accept the default option n . Choosing y will open the /etc/network/interfaces file for editing in vi editor to proceed with manual network configuration.

The above script configures Networking service, starts the service and adds it to the boot run level.

If your networking needs are more advanced, refer to the following detailed guide for manual network configuration.

Setting hostname

To set the system hostname:

# echo "shortname" > /etc/hostname

Then, to activate the change:

# hostname -F /etc/hostname

If you're using IPv6, you should also add the following special IPv6 addresses to your /etc/hosts file:

Contents of /etc/hosts

... ::1 localhost ipv6-localhost ipv6-loopback fe00::0 ipv6-localnet ff00::0 ipv6-mcastprefix ff02::1 ipv6-allnodes ff02::2 ipv6-allrouters ff02::3 ipv6-allhosts
Tip: If you're going to use automatic IP configuration, such as IPv4 DHCP or IPv6 Stateless Autoconfiguration, you can skip ahead to Configuring DNS. Otherwise, if you're going to use a static IPv4 or IPv6 address, continue below.

For a static IP configuration, it's common to also add the machine's hostname you just set (above) to the /etc/hosts file.

Here's an IPv4 example:

Contents of /etc/hosts

... 192.168.1.150 shortname.domain.com ...

And here's an IPv6 example:

Contents of /etc/hosts

... 2001:470:ffff:ff::2 shortname.domain.com ...

Configuring DNS

Tip: For users of IPv4 DHCP: Please note that /etc/resolv.conf will be completely overwritten with any nameservers provided by DHCP. If DHCP does not provide any nameservers, then /etc/resolv.conf will still be overwritten, but will not contain any nameservers!

For a static IP address and static nameservers, use one of the following examples.

For IPv4 nameservers, edit your /etc/resolv.conf file to look like this:
The following example uses Google's Public DNS servers.

Contents of /etc/resolv.conf

nameserver 8.8.8.8 nameserver 8.8.4.4

For IPv6 nameservers, edit your /etc/resolv.conf file to look like this:
The following example uses Hurricane Electric's public DNS server.

Contents of /etc/resolv.conf

nameserver 2001:470:20::2

You can also use Hurricane Electric's public IPv4 DNS server:

Contents of /etc/resolv.conf

nameserver 74.82.42.42
Tip: If you decide to use Hurricane Electric's nameserver, be aware that it is 'Google-whitelisted'. What does this mean? It allows you access to many of Google's services via IPv6. (Just don't add other, non-whitelisted, nameservers to /etc/resolv.conf — ironically, such as Google's Public DNS Servers.) Read here for more information.

Interface configuration

Loopback configuration

To configure loopback, add the following to the file /etc/network/interfaces:

Contents of /etc/network/interfaces

auto lo iface lo inet loopback

The above works to set up the IPv4 loopback address (127.0.0.1), and the IPv6 loopback address (::1) — if you enabled IPv6.

Warning: Loopback configuration is mandatory and must appear first in /etc/network/interfaces to prevent networking issues.


Wireless configuration

Main article: Wi-Fi

wpa_supplicant and iwd are the two wireless daemons supported in Alpine Linux. For manual interface configuration as explained in this page, eth0 can be substituted by the appropriate wireless interface i.e wlan0.

Ethernet configuration

For the following Ethernet configuration examples, we will assume that you are using Ethernet device eth0.

ifupdown-ng configuration

If ifupdown-ng package is used, instructions in the following section can be followed. You may check the availability of ifupdown-ng package via the command ifquery --version. ifupdown-ng tools supports udhcpc from BusyBox and dhcpcd. Of these, only dhcpcd can interact with both DHCP and DHCPv6 from the same process, which ifupdown-ng requires. Thus the IPv4 DHCP configuration given on this page will also result in the use of DHCPv6, but only if the dhcpcd package is installed. The ifupdown-ng scripts prioritize dhcpcd over udhcpc as per /usr/libexec/ifupdown-ng/dhcp script.

Note: dhclient is no longer available in Alpine Linux since v3.21
Basic configuration

A basic configuration for a desktop computer involves using the DHCP helper to learn an IPv4 address dynamically appears as follows:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 use dhcp
IPv6 RA configuration

With IPv6, stateless auto-configuration is typically used to configure network interfaces. If you are not interested in using IPv4 at all, you can simply use the ipv6-ra executor to ensure that an interface is configured to accept IPv6 RA advertisements:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 use ipv6-ra
Static configuration

To configure static IPv4 and IPv6 addresses, use of the address keyword, will automatically be used to configure the interface:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 address 203.0.113.2/24 gateway 203.0.113.1
Multiple address

A typical scenario on servers is where a server has multiple IP addresses on a single interface. In this case you simply add additional address lines like this:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 address 203.0.113.2/24 address 203.0.113.3/24 address 203.0.113.4/24 gateway 203.0.113.1
Dual-stack configuration

Servers can also be configured to run a dual-stack configuration, where interfaces have both an IPv4 and an IPv6 address. This is accomplished in a similar way as multi-homing. You specify the IPv4 and IPv6 addresses you want, followed by gateways for each:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 address 203.0.113.2/24 address 203.0.113.3/24 address 203.0.113.4/24 gateway 203.0.113.1 address 2001:db8:1000:2::2/64 address 2001:db8:1000:2::3/64 address 2001:db8:1000:2::4/64 gateway 2001:db8:1000:2::1
Note: If ifupdown-ng package is not available, do not use 192.168.1.150/24 format and instead use only the below format:

Contents of /etc/network/interfaces

address 192.168.1.150 netmask 255.255.255.0

Busybox ifupdown configuration

IPv4 DHCP configuration

Add the following to the file /etc/network/interfaces, as follows:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet dhcp

By default, the busybox DHCP client (udhcpc) requests a static set of options from the DHCP server. If you need to extend this set, you can do so by setting some additional command line options for the DHCP client, via the udhcpc_opts in your interface configuration. The following example requests domain-search option:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet dhcp udhcpc_opts -O search

For a complete list of command line options for udhcpc, see this document.

IPv4 Static Address Configuration

Add the following to the file /etc/network/interfaces, below the auto eth0 definition:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet static address 192.168.1.150 netmask 255.255.255.0 gateway 192.168.1.1
Additional IP addresses

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet static address 192.168.1.150 netmask 255.255.255.0 gateway 192.168.1.1 iface eth0 inet static address 192.168.1.151 netmask 255.255.255.0
IPv6 Stateless Autoconfiguration

Add the following to the file /etc/network/interfaces:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet6 auto
IPv6 Static Address Configuration

Add the following to the file /etc/network/interfaces, below the auto eth0 definition:

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet6 static address 2001:470:ffff:ff::2 netmask 64 gateway 2001:470:ffff:ff::1 pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra
Dual-Stack Configuration

This example shows a dual-stack configuration.

Contents of /etc/network/interfaces

... auto eth0 iface eth0 inet static address 192.168.1.150 netmask 255.255.255.0 gateway 192.168.1.1 iface eth0 inet6 static address 2001:470:ffff:ff::2 netmask 64 gateway 2001:470:ffff:ff::1 pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra

Networking service

Changes made to /etc/network/interfaces can be activated by running:

# rc-service networking restart

To start (or restart) the networking service:

# rc-service networking --quiet start &

To add networking service so that it starts on boot:

# rc-update add networking boot

Firewall

Alpine Linux provides multiple firewall software. Some of the prominent ones are listed below:

Troubleshooting

Connectivity testing

Test if networking is configured properly by attempting to ping out:

$ ping www.google.com PING www.l.google.com (74.125.47.103) 56(84) bytes of data. 64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=1 ttl=48 time=58.5 ms 64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=2 ttl=48 time=56.4 ms 64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=3 ttl=48 time=57.0 ms 64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=4 ttl=48 time=60.2 ms ^C --- www.l.google.com ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3007ms rtt min/avg/max/mdev = 56.411/58.069/60.256/1.501 ms

For an IPv6 traceroute run traceroute6:

$ traceroute6 ipv6.google.com traceroute to ipv6.l.google.com (2001:4860:8009::67) from 2001:470:ffff:ff::2, 30 hops max, 16 byte packets 1 2001:470:ffff:ff::1 (2001:470:ffff:ff::1) 3.49 ms 0.62 ms 0.607 ms 2 * * * 3 * * * 4 pr61.iad07.net.google.com (2001:504:0:2:0:1:5169:1) 134.313 ms 95.342 ms 88.425 ms 5 2001:4860::1:0:9ff (2001:4860::1:0:9ff) 100.759 ms 100.537 ms 89.907 ms 6 2001:4860::1:0:5db (2001:4860::1:0:5db) 115.563 ms 102.946 ms 106.191 ms 7 2001:4860::2:0:a7 (2001:4860::2:0:a7) 101.754 ms 100.475 ms 100.512 ms 8 2001:4860:0:1::c3 (2001:4860:0:1::c3) 99.272 ms 111.989 ms 99.835 ms 9 yw-in-x67.1e100.net (2001:4860:8009::67) 101.545 ms 109.675 ms 99.431 ms

iproute2

Install the iproute2 package which provides the 'ss' command which is an alternate to netstat.:

# apk add iproute2

Show listening tcp ports:

$ ss -tl

Show listening tcp ports and associated processes:

$ ss -ptl

Show listening and established tcp connections:

$ ss -ta

Show socket usage summary:

$ ss -s

Show more options:

$ ss -h

drill

Install drill (it will also install the 'ldns' package) which is a superior replacement for nslookup and dig etc:

# apk add drill

Then use it as you would for dig:

$ drill alpinelinux.org @8.8.8.8

To perform a reverse lookup (get a name from an IP) use the following syntax:

$ drill -x 8.8.8.8 @208.67.222.222

Missing interface

To list your available network interfaces use the commands ip link or ip a. Refer to Wifi troubleshooting page for issues related to wireless interfaces. If nothing works, you may have to use an alternate interface (e.g. a usb to ethernet adapter).

See also

You may also wish to review the following network related articles:

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