Currently, when one does not enable remounting the rootfs read-write,
i.e. keep it read-only, for example because the filesystem is actually
read-only by design, like squashfs, then two things happen:
- we create a factory from the content of /var at build time, register
tmpfiles entries for it, and mount a tmpfs on /var at runtime, so
that systemd-tmpfiles does populate /var from the factory; this is
only done when the rootfs is not remounted r/w;
- we trigger systemd-tmpfiles at build time, which uses the tmpfiles
db, of which our /var entries, to pre-populate the filesystem; this
is always done, whether the rootfs is remounted r/w or not.
Note that Buildroot mounts a tmpfs on /var, and leaves to the integrator
to care for providing an actual filesystem, as there are too many
variants and is very specific to each use-case.
These two mechanisms are conflicting, semantically, but also
technically: the files from the factory will be duplicated, but that
may help in some situations when the actual /var filesystem is not
mountable.
In some cases, it might be preferable to have none, either, or both
mechanisms enabled; it highly depends on the ultimate integration scheme
chosen for a device.
For example, some people will be very happy with a /var that is actually
on a tmpfs and that it gets reseeded form scratch at every boot, while
others may want to ensure that their system continue to work even when
they can't mount something that makes /var writable.
YMMV, as they used to say back in the day...
So, we introduce two new options, in the system sub-menu, each to drive
each mechanism. We default those options to y, to keep the previous
behaviour by default, except the var factory is only available when the
rootfs is not remounted r/w, as it were so far.
We still hint in the help text that there might be some conflict between
the two mechanisms, but since it has been that way for some time, it
does not look too broken for most people.
Since that introduces more options related to systemd being chosen as an
init system, we gather those two options and the existing one inside a
if-endif block, rather than adding more 'depends on' on each options.
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Norbert Lange <nolange79@gmail.com>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Romain Naour <romain.naour@smile.fr>
Cc: Jérémy Rosen <jeremy.rosen@smile.fr>
Cc: Yann E. MORIN <yann.morin@orange.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
3f79611b30