Re: [PATCH v3] expand-on-first-boot: Ensure that /tmp is writable

["'MOESSBAUER, Felix' via isar-users" <isar-users@googlegroups.com>]

On Tue, 2024-08-13 at 12:17 +0300, Uladzimir Bely wrote:
> On Thu, 2024-07-25 at 16:17 +0200, 'Clara Kowalsky' via isar-users
> wrote:
> > By setting PrivateTmp, a new file system namespace is created for
> > this
> > service and private /tmp/<service>/tmp and /var/tmp/<service>/tmp
> > subdirectories are mounted, which are only used for processes of
> > this
> > namespace. The service unit receives a mount unit dependency for
> > all
> > mounts required to access /tmp and /var/tmp.
> > This ensures that the /tmp directory is writable for the service,
> > as
> > mktemp is used in expand-last-partition.sh and creates a temporary
> > file.
> > 
> > Signed-off-by: Clara Kowalsky <clara.kowalsky@siemens.com>
> > ---
> >  .../expand-on-first-boot/files/expand-on-first-boot.service      |
> > 1
> > +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/meta/recipes-support/expand-on-first-
> > boot/files/expand-
> > on-first-boot.service b/meta/recipes-support/expand-on-first-
> > boot/files/expand-on-first-boot.service
> > index 90c92a39..8e76998b 100644
> > --- a/meta/recipes-support/expand-on-first-boot/files/expand-on-
> > first-boot.service
> > +++ b/meta/recipes-support/expand-on-first-boot/files/expand-on-
> > first-boot.service
> > @@ -16,6 +16,7 @@ Type=oneshot
> >  ExecStart=/usr/share/expand-on-first-boot/expand-last-partition.sh
> >  ExecStartPost=-/bin/systemctl disable expand-on-first-boot.service
> >  ExecStopPost=-/bin/systemctl disable expand-on-first-boot.service
> > +PrivateTmp=true
> >  
> >  [Install]
> >  WantedBy=sysinit.target
> > -- 
> > 2.45.2
> > 
> 
> Hello all.
> 
> After few days having this patch merged we at least twice faced the
> issue in CI with running qemuamd64 machine, probably related to the
> applied patch.
> 
> Error message is "ERROR| No resize output while expected". E.g.,
> there
> is no btrfs resize output in VM boot log.
> 
> The reason of non-running expand-on-first-boot serivce is:
> 
> ```
> [    5.578636] systemd[1]: local-fs-pre.target: Job expand-on-first-
> boot.service/start deleted to break ordering cycle starting with
> local-
> fs-pre.target/start
> ```

Interesting, I observed this same issue as well, but thought it comes
from a downstream part. You're right, this cannot work:

Citing systemd.exec:

Similarly, units with PrivateTmp= enabled automatically get mount unit
dependencies for all mounts required to access /tmp/ and /var/tmp/.
They will also gain an automatic After= dependency on systemd-tmpfiles-
setup.service(8). 

If /var is the partition to be resized, this will break.

Felix

> 
> I'm currently debugging the issue, but for now I'll attach two logs
> when the same image was run twice - with and without an error.
> 
> Maybe someone have some ideas about the issue.
> 
> Actually, in case expand-on-first-boot runs OK, there is another
> target
> systemd disables:
> 
> ```
> [    5.507289] systemd[1]: local-fs.target: Job local-fs-
> pre.target/start deleted to break ordering cycle starting with local-
> fs.target/start
> ```
> 
> -- 
> Best regards,
> Uladzimir.
> 

-- 
Siemens AG, Technology
Linux Expert Center


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