Using --add-host or extra hosts with docker-compose

Question

I am using docker-compose to run a test environment  that consists of about 5 different containers  The inter-container links and the shared volumes  volumes-from  works wonderfully  I also expose some ports up to the host machine  which works nicely   What I am missing is a way to link some of my real servers into this environment  without hardcoding ip address  With docker run  you could use --add-host to add another line in your  etc hosts file  Is there any way to do something similar with docker-compose

User · Answer

It seems like it should be made possible to say:

extra_hosts:
 - "loghost:localhost"

So if the part after the colon (normally an IP address) doesn't start with a digit, then name resolution will be performed to look up an IP for localhost, and add something like to the container's /etc/hosts:

127.0.0.1 loghost

...assuming that localhost resolves to 127.0.0.1 on the host system.

It looks like it'd be really easy to add in docker-compose's source code: compose/config/types.py's parse_extra_hosts function would likely do it.

For docker itself, this would probably be addable in opts/hosts.go's ValidateExtraHost function, though then it's not strictly validating anymore, so the function would be a little misnamed.

It might actually be a little better to add this to docker, not docker-compose - docker-compose might just get it automatically if docker gets it.

Sadly, this would probably require a container bounce to change an IP address.

User · Answer

This is in the feature backlog for Compose but it doesn t look like work has been started yet  Github issue

User · Answer

Basic docker-compose yml with extra hosts  version   3  services  api      build        ports          -  quot 5003 5003 quot      extra hosts          -  quot your-host name com 162 242 195 82 quot   host and ip         -  quot your-host--1 name com your-host--2 name com 50 31 209 229 quot   multiple hostnames with same ip           The content in the  etc hosts file in the created container  162 242 195 82  your-host name com 50 31 209 229   your-host--1 name com your-host--2 name com  You can check the  etc hosts file with the following commands    docker-compose -f path to file docker-compose yml run api bash     api  is service name  then inside container bash root f7c436910676  app  cat  etc hosts

User · Answer

I have great news  this will be in Compose 1 3  I m using it in the current RC  RC1  like this  rng    build  rng   extra hosts      seed  1 2 3 4     tree  4 3 2 1

User · Answer

https   docs docker com compose compose-file  extra hosts     extra hosts - Add hostname mappings     Uses the same values as the docker client --add-host parameter   extra hosts   -  somehost 162 242 195 82   -  otherhost 50 31 209 229        An entry with the ip address and hostname will be created in  etc hosts   inside containers for this service  e g   162 242 195 82  somehost 50 31 209 229   otherhost

[docker] Using --add-host or extra_hosts with docker-compose

Examples related to docker

Examples related to hosts

Examples related to docker-compose