Generic dnsmasq on Alpine image
Sometimes we need to quickly override DNS entries for testing purposes. dnsmasq provides an easy way to override a few DNS records, while still (recursively) resolving any other records.
This container is just Alpine Linux with dnsmasq installed.
Using the Pre-built Image
% docker pull suet/dnsmasq
Building the Image
% git clone https://github.com/su-et/dnsmasq.git
% cd dnsmasq
% docker build -t dnsmasq .
Running
You can either mount a hosts file:
% docker run -v hosts:/etc/hosts.dnsmasq dnsmasq:alpine
or, if you only need a single record, you can pass a host record on the command line:
% docker run dnsmasq:alpine --host-record=www.example.org,example.org,127.0.0.1,60
The --host-record syntax is hostname,ipv4,ipv6,ttl. Multiple hostnames can be specified (separated by commas); ipv4, ipv6, and ttl are all optional, although if no address is specified, the "real" record will be used (if it exists). If either, or both, addresses are specified without ttl, a TTL of 0 will be returned.
Examples:
Without any overrides
% dig +noall +answer @172.17.0.3 example.org
example.org. 4479 IN A 93.184.216.34
% dig +noall +answer @172.17.0.3 example.org aaaa
example.org. 4481 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
Replace the IPv6 address and TTL
Replace only the IPv6 address of example.org
docker run dnsmasq:alpine --host-record=example.org,::1,60
% dig +noall +answer @172.17.0.3 example.org
example.org. 4502 IN A 93.184.216.34
% dig +noall +answer @172.17.0.3 example.org aaaa
example.org. 60 IN AAAA ::1
Replace the IPv4 address and TTL
Replace only the IPv4 address of example.org
docker run dnsmasq:alpine --host-record=example.org,127.0.0.1,60
% dig +noall +answer @172.17.0.3 example.org
example.org. 60 IN A 127.0.0.1
% dig +noall +answer @172.17.0.3 example.org aaaa
example.org. 4502 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
Replace both addresses and TTL
docker run dnsmasq:alpine --host-record=example.org,127.0.0.1,::1,60
% dig +noall +answer @172.17.0.3 example.org
example.org. 60 IN A 127.0.0.1
% dig +noall +answer @172.17.0.3 example.org aaaa
example.org. 60 IN AAAA ::1
Docker Pull Command
docker pull suet/dnsmasq