* [Buildroot] crontab: can't change directory to '/var/spool/cron/crontabs': No such file or directory
2016-01-28 22:02 ` Peter Korsgaard
@ 2016-01-29 10:13 ` Luca Ceresoli
2016-02-01 18:17 ` Arnout Vandecappelle
1 sibling, 0 replies; 4+ messages in thread
From: Luca Ceresoli @ 2016-01-29 10:13 UTC (permalink / raw)
To: buildroot
Dear Alexey, Peter,
Peter Korsgaard wrote:
>>>>>> "Alexey" == Alexey Brodkin <Alexey.Brodkin@synopsys.com> writes:
>
> > Hello,
> > Just noticed this:
> ------------------> 8-------------------
> > # crontab -e
> > crontab: can't change directory to '/var/spool/cron/crontabs': No such file or directory
> ------------------> 8-------------------
>
> > Obvious solution is:
> ------------------> 8-------------------
> > # mkdir -p /var/spool/cron/crontabs
> ------------------> 8-------------------
>
> > But the question is if we want that to be done automatically and if
> > we do want how (read "where") to do it properly?
>
> Yes, the problem is also how should this work together with a readonly
> rootfs? Our default skeleton has /var/spool as a symlink to /tmp/, so we
> cannot add /var/spool/cron/crontabs at build time (unless we change the
> skeleton).
Yeah, changing the skeleton looks like a clean solution at first, but
it would potentially break existing configurations using /var/spool
with a readonly rootfs, and quietly change the behaviour of those with
a rw rootfs... Not good.
Another option, specific for crond and crontab, would be to change
CONFIG_FEATURE_CROND_DIR in the Busybox config so it points to
non-volatile storage. A candidate might be /var/cron, but according to
hier(7):
- /var/cron: Reserved for historical reasons.
- /var/spool/cron: Spooled jobs for cron(8).
A variant on this might be:
- store crontab files in /var/cron (or wherever in the rootfs)
- add a boot script that creates a symlink
/var/spool/cron -> /var/cron
- _not_ change the Busybox config.
>
> What I have done in the past is simply to do it in an init script,
> E.G. something like:
>
>
> # /var/spool is link to /tmp => crontabs are not persistent over boot
> mkdir -p /var/spool/cron/crontabs
> cp /root/crontab /var/spool/cron/crontabs/root
> start-stop-daemon -S -q -p /var/run/crond.pid --exec /usr/sbin/crond -- -l 9
>
> But that isn't very generic.
And it does not save /var/spool/cron/crontabs/root to /root/crontab
after edits, which is the worst drawback IMHO.
This is a topic we may discuss during the Developer Days next week.
--
Luca
^ permalink raw reply [flat|nested] 4+ messages in thread* [Buildroot] crontab: can't change directory to '/var/spool/cron/crontabs': No such file or directory
2016-01-28 22:02 ` Peter Korsgaard
2016-01-29 10:13 ` Luca Ceresoli
@ 2016-02-01 18:17 ` Arnout Vandecappelle
1 sibling, 0 replies; 4+ messages in thread
From: Arnout Vandecappelle @ 2016-02-01 18:17 UTC (permalink / raw)
To: buildroot
On 28-01-16 23:02, Peter Korsgaard wrote:
>>>>>> "Alexey" == Alexey Brodkin <Alexey.Brodkin@synopsys.com> writes:
>
> > Hello,
> > Just noticed this:
> ------------------> 8-------------------
> > # crontab -e
> > crontab: can't change directory to '/var/spool/cron/crontabs': No such file or directory
> ------------------> 8-------------------
>
> > Obvious solution is:
> ------------------> 8-------------------
> > # mkdir -p /var/spool/cron/crontabs
> ------------------> 8-------------------
>
> > But the question is if we want that to be done automatically and if
> > we do want how (read "where") to do it properly?
>
> Yes, the problem is also how should this work together with a readonly
> rootfs? Our default skeleton has /var/spool as a symlink to /tmp/, so we
> cannot add /var/spool/cron/crontabs at build time (unless we change the
> skeleton).
I think it's a mistake that we have /var/spool as a symlink to /tmp. /var/spool
shouldn't contain any files directly. So instead, I think any package that needs
a /var/spool directory should create it either as a directory or as a symlink.
In the particular case of crontab, that should probably be a directory, not a
symlink, since it doesn't make much sense to have crontab files non-persistent.
In fact, dcron does create $(TARGET_DIR)/var/spool/cron/crontabs - which is
silly of course since it will just create a directory in /tmp and the tmpfs will
be mounted over it.
Of course, changing this may break other packages, probably at runtime only.
The following packages are currently referring to /var/spool from buildroot, but
there are probably a few others (including busybox) that refer to it from their
own Makefiles:
at boa busybox dcron dcron exim leafnode2 mutt smstools3
Regards,
Arnout
>
> What I have done in the past is simply to do it in an init script,
> E.G. something like:
>
>
> # /var/spool is link to /tmp => crontabs are not persistent over boot
> mkdir -p /var/spool/cron/crontabs
> cp /root/crontab /var/spool/cron/crontabs/root
> start-stop-daemon -S -q -p /var/run/crond.pid --exec /usr/sbin/crond -- -l 9
>
> But that isn't very generic.
>
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286500
Essensium/Mind http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint: 7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF
^ permalink raw reply [flat|nested] 4+ messages in thread