[systemd-devel] [PATCH] fstab-generator: Honor usr=, usrfstype= and usrflags=

[Tobias Hunger]

I will update the patch as soon as I get home :-)

Best Regards,
Tobias

PS: How do you send patches to this list via gmail? I pasted the output
from git format-patch into the mail client, bit there got to be a better
way:-)
On Oct 9, 2014 4:08 PM, "Lennart Poettering" <lennart at poettering.net> wrote:

> On Thu, 09.10.14 09:37, Tobias Hunger (tobias.hunger at gmail.com) wrote:
>
> > On Oct 8, 2014 2:15 PM, "Harald Hoyer" <harald.hoyer at gmail.com> wrote:
> > > > What is the rationale of this patch?
> > > > Supporting systems without /etc/fstab in the root device?
> > > > Overriding the /etc/fstab settings?
> > > >
> > > > In a systemd initrd (e.g. in dracut) as soon as
> initrd-root-fs.target is
> > > > reached, initrd-parse-etc.service is executed, which retriggers the
> > > > fstab-generator and reads fstab from the real root and generates
> units
> > for /usr.
> >
> > Hello Harald,
> >
> > The use case is exactly the one Lennart described in his blog about
> > deploying Linux in the future.
> >
> > My setup now looks like this: I got a Btrfs partition for my Linux
> > installations. This partition has a subvol root:somename:someid:x86_64
> > containing a Linux installation minus /use.
> >
> > Then I have several versions of /use for that distribution in more
> > subvolumes named usr:someid:x86_64:version (all with different versions,
> > basically getting incremented whenever a new set of packages gets
> > installed).
> >
> > The idea is to now be able to write bootloader entries for all versions
> the
> > somename-installation.
> >
> > For that the initrd needs to know which /usr to mount on top of the root
> > partition.
> >
> > I can not use the fstab from the root drive here, because that would
> always
> > point to the same version of /use, preventing me to roll back/forward
> when
> > something breaks during an upgrade.
> >
> > What I could do instead is to put the information about which subvol to
> > mount at /use into the initrd. But I actually think the way of passing
> this
> > into initrd in the same way as the rootfs is more consistent and it also
> > saves me from having a new initrd in /boot when libreoffice gets updated.
> > That *might* be necessary when using secure boot, but only then.
> >
> > Does this explain my motivation for this patch sufficiently?
>
> Hmm, so I think this should be merged, but I'd like to ask for one
> more change. We really want to avoid inventing new non-namespaced
> kernel command line options, that's really something we should leave
> to the kernel guys...
>
> Hence, I'd propose using "mount.usr=", "mount.usrflags=" and
> "mount.usrfstype="... Or maybe "fs." as prefix? Or "mnt."? But I think
> "mount." is the nicest one, even if it is slightly more to type.
>
> Hope that make sense?
>
> (OTOH I just yesterday merged a patch that introduced a new
> un-namespaced kernel cmdline option "rescue", so I am not totall fair
> here, but I think that's a special case...)
>
> Lennart
>
> --
> Lennart Poettering, Red Hat
>
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