Re: [PATCH] image: remove / entry from fstab template

["Moessbauer, Felix" <felix.moessbauer@siemens.com>]

On Thu, 2023-01-05 at 14:08 +0100, Florian Bezdeka wrote:
> On Tue, 2022-10-04 at 13:46 +0200, Henning Schild wrote:
> > An fstab entry for / should usually not be required. It just makes
> > a
> > rootfs less portable (USB vs. NFS, vs. SSD). The kernel is the one
> > that should know which fs to mount and how. That is done via a
> > bootloader.
> > 
> > Should additional mount options be needed for a concrete image, an
> > imager like wic might add an entry. i.e. for adding fspassno or
> > x-systemd.growfs
> > 
> > So to make the rootfs more generic and to allow imagers to add
> > their
> > individual / lines, instead of having to modify an existing one,
> > remove
> > the line from the template.
> > 
> > Signed-off-by: Henning Schild <henning.schild@siemens.com>
> 
> Hi all,
> 
> FYI: While trying to update Isar in one layer using LAVA tests we
> recognized that there is now a breaking change:
> 
> Previously the rootfs was mounted rw on ext4 images because we had
> the
> / line in /etc/fstab, triggering systemd-remount logic.
> 
> As the entry for the root (/) has been removed in /etc/fstab
> remounting
> does no longer happen. This breaks several LAVA tests here as well as
> start-qemu scripts. Adding "rw" to the kernel cmdline would be one
> option but we have a lot of LAVA job descriptions and even more
> start-
> qemu scripts in downstream layers.
> 
> Felix already send out patches to OE (open embedded) to address that
> in
> wic. Necessary Isar patches (wic update, ...) will follow soon.
> Thanks
> a lot Felix for taking over.

Hi Devs,

let me add some additional information:

- in OE, the fstab in the rootfs contains the / entry
- we added a patch to OE to let WIC handle the root partition, but this
had been reverted because it led to duplicated entries (which break
systemd-remount)

By that, we are no longer in sync with OE. Also considering the revert
of the WIC patch, this shows that OE want to keep the / entry in the
rootfs fstab for the meantime.

Instead of discussing fundamental aspects (like if the line should be
in the rootfs fstab or not) I vote for just integrating the
deduplication logic in WIC and re-add the / entry in the rootfs fstab.
This brings us in sync with OE again and from then on we can discuss
how the general design should look like.

Felix

> 
> Best regards,
> Florian
>