Add group_add to job docker config

[Kamilcuk]

Proposal

This is a proposal to add a group_add argument to docker task "config"-uration that will mimic the docker --group_add and docker compose group_add: options.

task "..." {
   driver = "docker"
   user = "user1:group1"
    config {
       image = "alpine"
       group_add = [
          "group1",
          "group2",
          "1234",
       ]
   }
}

From docker run --help:

  --group-add list                 Add additional groups to join

Use-cases

The use case is to run a user with more than one group. For example, there is an NFS share where directories are owned by specific, multiple, different groups.

Attempted Solutions

The solution or workaround is to create a custom image with Dockerfile where you RUN useradd && groupadd the required groups to the user.

Related:
#8066
@dnrce could you sign CLA? Thank you.
https://discuss.hashicorp.com/t/inject-default-user-group-for-docker-by-nomad-client/18895

[tgross]

@Kamilcuk can you do us a favor and revisit what you've written here and try to turn it into a specific proposal? This is a bunch of links and @-mentions of unrelated folks on a closed PR.

(Edit: thanks!)

[schmichael]

Thanks for clarifying the issue @Kamilcuk. Looks like a straightforward case of Nomad needing to implement an additional Docker configuration option. I updated the labels so we can pick it up someday.

These sorts of plugin improvements are good opportunities for contributions as well, so I added the good first issue label. The Docker config parameters generally follow a pretty standard path in https://github.com/hashicorp/nomad/blob/v1.5.5/drivers/docker/config.go

[github-actions]

I'm going to lock this issue because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.