Subject: bug#35662: Really relocatable binaries crash with Permission denied

From: Giovanni Biscuolo <[email-masked]>
Date: Wed, 15 May 2019 17:20:25 +0200

Hello Ludovic and Florian,

I cannot help here, just some thoughts

as you probably already know, Florian, ZFS is not supported in Linux for
various reasons, above all for a controversial licensing problem [1]

so using zfsonlinux (the ZFS Linux unofficial kernel module) is
basically calling for problems

Ludovic Courtès <[email-masked]> writes:

> "pelzflorian (Florian Pelz)" <[email-masked]> skribis:

[...]

>> The admins have confirmed that they use “Proxmox on ZFS” (judging from
>> <https://pve.proxmox.com/wiki/ZFS_on_Linux> it is ZFS on Linux)

it's not clearly stated there, I guess it's
https://github.com/zfsonlinux/zfs

>> and
>> they have confirmed that they have disabled user namespaces in their
>> Proxmox settings.

I do not understand what this means: if namespaces are disabled **in
kernel** that whould be detected and guix relocatable binaries should
use PRoot by default: am I wrong?

If "disabled user namespace in Promox settings" means it have something
to do with ZFS filesystem settings, well: it's unorthodox at least :-)

> User namespaces are orthogonal to file systems, but anyway it looks like
> ZFS is refusing to let us do these things.

I don't know if this have something to do with this bug, but:

ZFS is confused by user namespaces (uid/gid mapping) when used with acltype=posixacl
https://github.com/zfsonlinux/zfs/issues/4177

Florian: it should be solved but AFAIU it depends on the
kernel/zfsonlinux combination

> I don’t have any great option to offer.  You could perhaps modify
> run-in-namespace.c so that it doesn’t even try user namespaces and
> instead goes directly to the PRoot option?

Ludovic (and others): is it possible to add an option to "guix pack -RR"
(-RRF?!?) to force the use of PRoot for resulting relocated binaries?

> However working around this behavior of ZFS it not completely trivial
> and I’m not sure we should put much energy to paper over non-standard
> file system behavior.

I agree, this seems a zfsonlinux bug: Florian please can you report it
upstream to zfsonlinux?

[...]

HTH! Gio'

[1] https://www.fsf.org/licensing/zfs-and-linux
    https://sfconservancy.org/blog/2016/feb/25/zfs-and-linux/

-- 
Giovanni Biscuolo

Xelera IT Infrastructures