Hi Ludo,

On Thu, 10 Jan 2019 09:59:02 +0100
Ludovic Courtès <ludo@gnu.org> wrote:

> Cgroup file systems are mounted by the corresponding file system
> services:
> 
> --8<---------------cut here---------------start------------->8---
> $ sudo herd status | grep cgroup
>  + file-system-/sys/fs/cgroup
>  + file-system-/sys/fs/cgroup/blkio
>  + file-system-/sys/fs/cgroup/cpu
>  + file-system-/sys/fs/cgroup/cpuacct
>  + file-system-/sys/fs/cgroup/cpuset
>  + file-system-/sys/fs/cgroup/devices
>  + file-system-/sys/fs/cgroup/elogind
>  + file-system-/sys/fs/cgroup/freezer
>  + file-system-/sys/fs/cgroup/memory
>  + file-system-/sys/fs/cgroup/perf_event
> --8<---------------cut here---------------end--------------->8---
> 
> Should it depend on ‘file-system-/sys/fs/cgroup/elogind’, or maybe both
> ‘elogind’ and ‘file-system-/sys/fs/cgroup/elogind’?  Depends on what it
> expects from elogind I guess…

Oh!

I think Docker doesn't expect anything from elogind.

Docker uses these cgroups and these capabilities:

* "memory": memory limit
* "memory": swap limit
* "memory": memory swappiness
* "memory": memory soft limit
* "memory": kernel memory limit
* "pids": pids limit
* "cpu": cpu cfs period/quota
* "cpu": CPU shares
* "cpu": CPU cfs
* "cpuset": cpus, mems
* "blkio": Block I/O weight
* "blkio": BPS Block I/O read limit
* "blkio": BPS Block I/O write limit
* "blkio": IOPS Block I/O read limit
* "blkio": IOPS Block I/O write limit
* "devices": List devices

Can I just repeat

 (service-extension file-system-service-type (const %elogind-file-systems))

[or a subset thereof]

in the docker service type and not have to have elogind in the config
at all?  Is that safe?  (i.e. will it mount the file systems just once?)