Re: [RFC PATCH] virtfs: 9p: local: add default uid and gid options

[Warner Losh <imp@bsdimp.com>]

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On Sat, Dec 6, 2025, 10:12 AM Andrey Erokhin <language.lawyer@gmail.com>
wrote:

> On 03/12/2025 15:33, Christian Schoenebeck wrote:
> > On Monday, 1 December 2025 19:00:53 CET Andrey Erokhin wrote:
> >> I was trying to boot from a directory tree owned by an ordinary user,
> >> and some daemons weren't happy about non-root ownership of some files
> >>
> >> Example use:
> >> -virtfs
> local,path=rootfs,mount_tag=root,security_model=mapped,uid=0,gid=0
> >>
> >> Works with any security_model
> >
> > First I thought do we really want to open that rabbit hole and add
> permission management to the CLI options? However I get why this might be
> useful for  mapped[-*] security models.
> > But for passthrough it is not of any use, is it?
>
> Prolly none, just a side effect of how it's implemented.
> Can either make it an error when used with passthrough, or ignore them
> (use default -1 value) when copying options to 9p fs context (with or
> without a warning)
>
> > Also while it is very handy to have a short option name like "uid" and
> "gid", for the sake of long term progression and clarity an option name
> like "default-uid" would be more appropriate.
>
> Or rather default_uid, to match other options style? But uid/gid also
> kinda match fmode/dmode :\
>

FreeBSD has a mode where you can build the image where the files in the
filesystem are owned by the user with random permission bits, but the
actual owners / modes are in an mtree formatted file. The nopriv imagers
combine the two when making images. It would be nice to have p9 do a
simular mapping for the guest so I can boot test these images more directly
w/o the copyout to the "bootable image". The set the uid feature would
help, true, but leaves me wanting more.

Warner

> The patch is also missing the required documentation changes for these
> new options BTW.
>
> Haven’t added them yet, wasn’t sure there would be interest in this feature
>
>

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