Configure Networking
This page will assist you in setting up networking on Alpine Linux.
Setting System Hostname
To set the system hostname, do something like the following:
echo "shortname" > /etc/hostname
Then, to activate the change, do the following:
hostname -F /etc/hostname
If you're using IPv6, you should also add the following special IPv6 addresses to your /etc/hosts file:
::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
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:
192.168.1.150 shortname.domain.com
And here's an IPv6 example:
2001:470:ffff:ff::2 shortname.domain.com
Configuring DNS
/etc/resolv.conf will be completely overwritten with any nameservers provided by DHCP. Also, if DHCP does not provide any nameservers, then /etc/resolv.conf will still be overwritten, but will not contain any nameservers!For using a static IP 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.
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.
nameserver 2001:470:20::2
You can also use Hurricane Electric's public DNS server via IPv4:
nameserver 74.82.42.42
/etc/resolv.conf — ironically, such as Google's Public DNS Servers.) Read here for more information.Enabling IPv6 (Optional)
If you use IPv6, do the following to enable IPv6 for now and at each boot:
modprobe ipv6 echo "ipv6" >> /etc/modules
Interface Configuration
Loopback Configuration (Required)
/etc/network/interfaces to prevent networking issues.To configure loopback, add the following to a new file /etc/network/interfaces:
auto lo iface lo inet loopback
The above works to setup the IPv4 loopback address (127.0.0.1), and the IPv6 loopback address (::1) — if you enabled IPv6.
Wireless Configuration
See Connecting to a wireless access point.
Ethernet Configuration
For the following Ethernet configuration examples, we will assume that you are using Ethernet device eth0.
Initial Configuration
Add the following to the file /etc/network/interfaces, above any IP configuration for eth0:
auto eth0
IPv4 DHCP Configuration
Add the following to the file /etc/network/interfaces, below the auto eth0 definition:
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 it by setting some additional command line options for the DHCP client, via the udhcpc_opts in your interface configuration. The following example additionally requests domain-search option:
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:
iface eth0 inet static
address 192.168.1.150
netmask 255.255.255.0
gateway 192.168.1.1
Additional IP addresses
Repeat this stanza to add an additional IP address to the interface.
IPv6 Stateless Autoconfiguration
Add the following to the file /etc/network/interfaces, below the auto eth0 definition:
iface eth0 inet6 manual
pre-up echo 1 > /proc/sys/net/ipv6/conf/eth0/accept_ra
IPv6 Static Address Configuration
Add the following to the file /etc/network/interfaces, below the auto eth0 definition:
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
Example: Dual-Stack Configuration
This example shows a dual-stack configuration.
auto lo
iface lo inet loopback
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
Firewalling with iptables and ip6tables
See also: Alpine Wall - How-To Alpine Wall - Alpine Wall User's Guide
Install iptables/ip6tables
- To install iptables:
apk add iptables
- To install ip6tables:
apk add ip6tables
- To install the man pages for iptables and ip6tables:
apk add iptables-doc
Configure iptables/ip6tables
Save Firewall Rules
For iptables
- Set iptables to start on reboot
rc-update add iptables
- Write the firewall rules to disk
/etc/init.d/iptables save
- If you use Alpine Local Backup:
- Save the configuration
lbu ci
- Save the configuration
For ip6tables
- Set ip6tables to start on reboot
rc-update add ip6tables
- Write the firewall rules to disk
/etc/init.d/ip6tables save
- If you use Alpine Local Backup:
- Save the configuration
lbu ci
- Save the configuration
Activating Changes and Testing Connectivity
Changes made to /etc/network/interfaces can be activated by running:
/etc/init.d/networking restart
If you did not get any errors, you can now test that 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 (traceroute6), you will first need to install the iputils package:
apk add iputils
Then 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
Additional Utilities
iproute2
You may wish to install the 'iproute2' package (note that this will also install iptables if not yet installed)
apk add iproute2
This provides the 'ss' command which is IMHO a 'better' version of netstat.
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
You may also wish to install 'drill' (it will also install the 'ldns' package) which is a superior (IMHO) 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
Related articles
You may also wish to review the following network related articles: