[Buildroot] [PATCH] system/skeleton: make /var/run a symlink to /run

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

On Wed, 15 Jul 2020 15:53:12 +0200
Norbert Lange <nolange79@gmail.com> wrote:

> > But... /run is already a tmpfs in sysv-based systems, so what prevents
> > today from using /run/lttng even for sysv based systems ?  
> 
> Ok, I missed that bit, thought it would have unrelated /run and
> /var/run directories.
> So this patch is just a cleanup then, and buildroot already *always*
> uses a tmpfs /run (with compatibilty symlink /var/run),
> and I can use /run with lttng and dbus whether this cleanup is merged or not?
> 
> I'd redo the patch with those removed, if you agree:
> 
> package/skeleton-init-openrc/skeleton/var/run
> package/skeleton-init-sysv/skeleton/var/run
> 
> Or do nothing if you dont ;)
> My new argument would be that this would prevent false assumptions (like mine).

OK, the more I look into this, the more I'm confused. To me, it seems
like in both systemd *and* non-systemd cases, /var/run is already a
symlink to /run, but just implemented in a different way.

For the systemd case, we have:

        ln -s ../run $(TARGET_DIR)/var/run

in package/skeleton-init-systemd/skeleton-init-systemd.dmk.

For the sysv/openrc case, we have the skeleton itself that contains:

$ ls -l package/skeleton-init-sysv/skeleton/var/run 
lrwxrwxrwx 1 thomas thomas 6 26 mars  17:10 package/skeleton-init-sysv/skeleton/var/run -> ../run
$ ls -l package/skeleton-init-openrc/skeleton/var/run 
lrwxrwxrwx 1 thomas thomas 6 18 mai   17:32 package/skeleton-init-openrc/skeleton/var/run -> ../run

So, it all cases, /var/run is already a symlink to /run. Am I missing
something here ?

So, if anything needs to be done, it's just cleaning up that and doing
it in the same way for all init systems, perhaps in a common place. But
we need to be careful, skeleton-init-systemd.mk has some
special/complex logic to handle /var and generate a
/etc/tmpfiles.d/var-factory.conf to generate the contents of /var at
boot time when the rootfs is read only and therefore the entire /var is
in tmpfs.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com