If you register a hostname with . at start, then all subdomains will solve to that container/local storage entry
Example
$ docker run --rm --hostname .mageddo.com nginx:latest
Now all mageddo.com subdomains will solve to that nginx container
$ nslookup site1.mageddo.com
Server: 172.17.0.4
Address: 172.17.0.4#53
Non-authoritative answer:
Name: site1.mageddo.com
Address: 172.17.0.5
$ nslookup mageddo.com
Server: 172.17.0.4
Address: 172.17.0.4#53
Non-authoritative answer:
Name: mageddo.com
Address: 172.17.0.5
From DPS 3.14 regex is also supported on localstorage or docker container hostname/HOSTNAMES env,
the pattern is /${REGEX}/, everything around the slashes is considered as regex
Example:
Running a sample container
$ docker run --rm --name nginx1 --hostname '/batata\.[a-z]+\.com/' -e 'HOSTNAMES=/\d+\.acme\.com/,/sub\.acme\.com/' nginx
Solving
$ nslookup batata.whatever.com
Server: 127.0.0.1
Address: 127.0.0.1#53
Non-authoritative answer:
Name: batata.whatever.com
Address: 172.17.0.4
$ nslookup xpto.acme.com
Server: 127.0.0.1
Address: 127.0.0.1#53
** server can't find xpto.acme.com: NXDOMAIN
$ nslookup 123.acme.com
Server: 127.0.0.1
Address: 127.0.0.1#53
Non-authoritative answer:
Name: 123.acme.com
Address: 172.17.0.4
$ nslookup sub.acme.com
Server: 127.0.0.1
Address: 127.0.0.1#53
Non-authoritative answer:
Name: sub.acme.com
Address: 172.17.0.4