[Buildroot] [PATCH 16/20] system: separate sysv and systemd parts of the skeleton

[Yann E. MORIN <yann.morin.1998@free.fr>]

Arnout, All,

On 2017-07-23 02:08 +0200, Arnout Vandecappelle spake thusly:
> On 18-07-17 19:25, Yann E. MORIN wrote:
> > systems does not like that the content of /var be symlinks to /tmp,
>   systemd
> 
> > especially journald that starts before /tmp is mounted, and thus the
> > journal files are hidden from view, which causes wuite a bit if fuss...
>                                                    quite
> > 
> > Instead, move the current /var to a sysv-only skeleton.
> > 
> > systemd at install time will create the /var content it needs, so we
> 
>  I guess systemd will also create a tmpfs on /var?

No it does not. But so far we do not support systemd on a read-only
root filesystem anyway (see the depends on for systemd).

In a later patch, we add support for a read-only rootfs, and then we add
an explicit tmpfs mont on /var, which systemd does not do on its own,
which is the reason for 886f3109bc (system: systemd only really supports
a R/W rootfs)

> > just create an empty /var for systemd. Yet, systemd really requires a
> > bunch of extra directories to exist, so we also create those.
> > 
> > Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> > Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
> 
>  Commit message needs to be improved (see also below), but with that
> Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
> 
> > 
> > ---
> > Note: /home and /srv will be created at runtime if missing, but it is
> > better to create them right now, to simplify supporting systemd on a
> > RO filesystem in the (near) future.
> > ---
> >  package/skeleton-systemd/skeleton-systemd.mk              | 7 +++++++
> >  package/skeleton-sysv/skeleton-sysv.mk                    | 4 ++++
> >  {system => package/skeleton-sysv}/skeleton/dev/log        | 0
> >  {system => package/skeleton-sysv}/skeleton/dev/pts/.empty | 0
> >  {system => package/skeleton-sysv}/skeleton/dev/shm/.empty | 0
> 
>  I guess indeed the /dev stuff is not needed for systemd because there is anyway
> a devtmpfs mounted over it. Which makes me wonder: shouldn't these be moved to
> the device-table? Only the static devices case needs these to be present... Of
> course, such a change is not for this patch, but I'd say that we can just leave
> this /dev stuff in the common part - systemd has no less use of it than sysv.
> 
> >  {system => package/skeleton-sysv}/skeleton/etc/fstab      | 0
> 
>  Why? systemd does use fstab, so it seems weird not to have an fstab in the
> systemd case.

We do have one, it is created in the skeleton-systemd.mk file:

    define SKELETON_SYSTEMD_INSTALL_TARGET_CMDS
            mkdir -p $(TARGET_DIR)/home
            mkdir -p $(TARGET_DIR)/srv
            mkdir -p $(TARGET_DIR)/var
            echo "/dev/root / auto rw 0 1" >$(TARGET_DIR)/etc/fstab
    endef

> Well, I guess our skeleton fstab doesn't contain anything relevant
> for systemd because all of that is handled already by tmpfiles.

Exactly.

> But the commit log should at least explain this.

Like so, maybe?

    For systemd, we only ever need an entry for /, because all the rest
    is totally irrelevant for systemd (it automatically mounts what it
    needs where it needs it).

Regards,
Yann E. MORIN.

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