overlayfs-etc compatibility with volatile-bind

overlayfs-etc compatibility with volatile-bind

[Baruch Siach]

Hi Vyacheslav Yurkov,

overlayfs-etc generates a 'preinit' script that unconditionally remounts
root to make it writable. Later systemd-fstab-generator generates a
mount unit (-.mount) that restores read-only as set in /etc/fstab.

I added an entry to VOLATILE_BINDS for the /home directory. The volatile-binds
recipe creates a systemd mount unit with the condition

  ConditionPathIsReadWrite=!/home

The trouble is that there is no dependency between the rootfs mount unit and
the /home unit. When the /home unit runs first, the condition is false, and
the unit fails. If I later start the /home unit manually, it succeeds, because
rootfs is read-only now.

What is the purpose of mounting root rw in 'preinit'?

Is there any other alternative to make volatile-binds do the right thing?

Thanks,
baruch

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -

Re: overlayfs-etc compatibility with volatile-bind

[Vyacheslav Yurkov]

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Hi Baruch

> What is the purpose of mounting root rw in 'preinit'?

I guess that was a default, which was not tested with other options
combined.

Do you use read-only-rootfs image feature? I think the script can be
adapted to take that into account.

Thanks,
Slava

On Wed, Feb 7, 2024, 10:30 Baruch Siach <baruch@tkos.co.il> wrote:

> Hi Vyacheslav Yurkov,
>
> overlayfs-etc generates a 'preinit' script that unconditionally remounts
> root to make it writable. Later systemd-fstab-generator generates a
> mount unit (-.mount) that restores read-only as set in /etc/fstab.
>
> I added an entry to VOLATILE_BINDS for the /home directory. The
> volatile-binds
> recipe creates a systemd mount unit with the condition
>
>   ConditionPathIsReadWrite=!/home
>
> The trouble is that there is no dependency between the rootfs mount unit
> and
> the /home unit. When the /home unit runs first, the condition is false, and
> the unit fails. If I later start the /home unit manually, it succeeds,
> because
> rootfs is read-only now.
>
> What is the purpose of mounting root rw in 'preinit'?
>
> Is there any other alternative to make volatile-binds do the right thing?
>
> Thanks,
> baruch
>
> --
>                                                      ~. .~   Tk Open
> Systems
> =}------------------------------------------------ooO--U--Ooo------------{=
>    - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -
>

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