‘guix system vm’ and shared store

[ludo@gnu.org (Ludovic Courtès)]

Hi,

David Craven <david@craven.ch> skribis:

> So guix doesn't work inside a vm - because /gnu/store is mounted
> readonly.

Right, and also because ‘guix system vm’ creates a VM that shares its
store with the host system.

> To be able to offload arm builds once guix system vm
> --system=armhf-linux works, /gnu/store needs to be writeable.
>
> Can multiple daemons concurrently use the same store?

No.

> or alternatively, can we move the
>
> (unless (zero? (system* unionfs "-o"
>
> "cow,allow_other,use_ino,suid,dev,max_files=65536"
>                                 "/rw-root=RW:/real-root=RO"
>                                 "/root"))
>           (error "unionfs failed"))
>
> to after the 9p filesystems have been mounted, so that the unionfs
> allows writing to /gnu/store too?

Yes, something like that: we need to make /gnu/store a union of the
host’s /gnu/store and a writable tmpfs, and we need to make sure
/var/guix/db/db.sqlite is populated appropriately (images produced by
‘guix system vm-image’ do the latter.)

HTH!

Ludo’.