Flux-core: docker: start munge daemons by default

[SteVwonder]

Per #2915, it would be cool if the default initial program for the docker image started munge (and any other necessary daemons) by default, so that you do not have to use our docker-run-checks.sh script if you are just poking at Flux.

Specifically, my intention is to enable this use case:

> docker run -ti fluxrm/flux-sched:latest
<starting container>
$ flux start
$ flux mini run hostname

Maybe we even have it start the flux instance by default :thinking:

[dongahn]

Maybe I'm using script incorrectly but docker-run-checks.sh doesn't start up munge either. I always manually start it. Munge startup may be implemented only in Travis CI recipe.

[grondo]

Yeah, it is run by travis_run.sh.

Currently, the CMD of the published docker image is set to /usr/bin/flux by docker-run-checks.sh before pushing to docker hub.

We could instead add an entrypoint.sh which runs runuser -u munge /usr/sbin/munged && flux start and that might work.

[grondo]

BTW, you don't need MUNGE running when using docker-run-checks.sh unless you build with --with-flux-security

[dongahn]

How do you avoid this in flux-sched? I don't configure my sched build with this option under docker but I still need munge...

[grondo]

How do you avoid this in flux-sched? I don't configure my sched build with this option under docker but I still need munge...

Oh, yeah, flux-sched is building against published flux-core docker image, which is built with --with-flux-security...

[SteVwonder]

Oh, yeah, flux-sched is building against published flux-core docker image, which is built with --with-flux-security...

Ah! Maybe this should actually be an issue under flux-sched then. If others agree, let's transfer the issue to the other repo.

[grondo]

Ah! Maybe this should actually be an issue under flux-sched then. If others agree, let's transfer the issue to the other repo.

Yeah, it would need to be fixed in both places probably. The nice thing about fixing it for the flux-core image is that flux-sched (and other framework project) developers would not need to manually start MUNGE if running docker-run-checks.