Re: Seeking best-practice for managing guix-defined VMs

[Ludovic Courtès]

Hello,

Hartmut Goebel <address@hidden> skribis:

> I wonder about the best-practice for managing VMs built using `guix
> system vm`.

I’d recommend letting ‘guix system vm’ manage the stateless part of the
VM, and if there’s any state, store it in a separate directory shared
with the host with “--share”.

> My idea is to have the system-configuration on the (foreign distro) host
> and build and run VMs using `guix system vm`. Background is that for
> some reasons I can not use GuixSD on the host, but wont to use guix for
> managing the actual work-horses.
>
> * For specifying the parameters of the host-side of the VM-emulation,
> and for starting the VM with the appropriate parameters, I can add a
> wrapper shell-script. Is there a better way than a shell-script?
>
> * When updating the config, the currently running VM needs to be shut
> down. What are good ways to handle this? How to notice, which is the
> correct VM to shut down (this one's "predecissor")?

‘guix system’ won’t help you with that.  You’ll have to do your own
bookkeeping I guess.

> * Over time, the store will fill up with `xxx-run-vm.sh` scripts. Will
> these be garbage-collected? (I assume not.) What are good ways to keep
> track of scripts and discard those no longer needed (and garbage-collect)?

Like everything in /gnu/store, ‘guix gc’ will delete them if they are
unused and unreachable.

> * How to handle "secrets", which need to go into the machine? Obviously
> it's not a good idea to have them in a system-declaration. OTO the VM's
> disk gets discarded with the next system generation.

Everything Guix manages ends up world-readable in /gnu/store.  So you
need an out-of-band channel for secrets, such as --share.

> * Is using `guix system vm` the wrong approach at all? Should I better
> use `vm-image` or `container`?

I think ‘guix system vm’ is fine.  The key is to clearly separate the
stateless part (software deployment) from state (secrets, databases,
etc. that your applications may need.)

HTH,
Ludo’.