Hi,
I would really like all distros that use systemd and mdadm to use a common
set of unit files to run mdadm. Similarly I would like us all to use
exactly the same udev rules files.
This is, after all, one of the benefits of open source - sharing fixes so we
all get a better result. It should also make it easier to respond to
community issues because there are fewer differences between distros.
To this end:
- I've recently added some systemd unit files to mdadm and they are or will
be in openSUSE. I'm hoping they will eventually make their way into
Fedora and any other distro that uses systemd. I am of course happy to
make changes to meet needs in other distros that I'm not aware of.
The particular unit files are:
mdadm-last-resort@.timer mdadm-last-resort@.service
When udev runs "mdadm -I" and finds that the array could have been
started degraded, but wasn't because there is good reason to believe
that more devices will appear, it adds to SYSTEMD_WANTS
mdadm-last-resort@mdXXX.timer
This waits 30 seconds and then runs mdadm-last-resort@mdxxx.service
which starts the array if possible.
If another device has appeared and the array has already been started,
this will simply do nothing.
This means that if you shut down, remove a device, then reboot you get
a 30 second pause and the array starts. That is better than the
current situation where the array doesn't start.
http://git.neil.brown.name/?p=mdadm.git;a=commitdiff;h=169ffac7ad7748c8586fd1d68b7a417d71133140
mdmonitor.service
This is similar in purpose to the mdmonitor.service from Fedora, but
different in detail. In particular whenever a RAID[1-9]* array starts,
udev adds this service to SYSTEMD_WANTS so that "mdadm --monitor" will
automatically be started when needed, but never before. So there is no
need to explicitly "enable" this service.
Doug/Jes: do you see a problem with switching to this in due course?
http://git.neil.brown.name/?p=mdadm.git;a=commitdiff;h=61c094715836e76b66d7a69adcb6769127b5b77d
- I've had a look at the Fedora udev rules files and brought a few ideas
across to the udev files in the mdadm distro. They are possibly
irrelevant for other distros, but they shouldn't hurt. There was a
bug-fix though.
There are a few bits that I haven't brought in yet, mostly relating to
the state of DM devices.
http://git.neil.brown.name/?p=mdadm.git;a=commitdiff;h=05ec50a57badfd220373aa06afd7d3fac0beb49f
http://git.neil.brown.name/?p=mdadm.git;a=commitdiff;h=25392f5fc59f96fb766ecb5617d5276f8c87d489
So if there are any distro maintainers out there (or anyone else who might
be interested), I'd love to hear about other things that might need to be in
common unit or rules files. Having said that though I'll shortly be going
on Christmas/New Year leave so I'm not expecting a quick resolution to all
of this. I'm happy to collect ideas though and would like to have something
fairly coherent before 3.3.1 which I'd like to see in February.
I'm quite aware that distro will have real differences for various reasons.
If at all possible I'd like to be able to localise those to separate files.
One example is the way arguments are passed to "mdadm --monitor" by
mdmonitor.service.
Fedora appears to not pass many arguments - presumably the important values
are in /etc/mdadm.conf.
openSUSE does pass lots of arguments generated from information
in /etc/sysconfig/mdadm (which is edited directly by our sysadmin tool
"yast").
The mdmonitor.service file I have written will run a script
/usr/lib/systemd/scripts/mdadm_env.sh
and then read environment variables from /run/sysconfig/mdadm. The script
writes there and a value written there is used as the arguments for mdadm.
I've included a SUSE-specific version of mdadm_env.sh. Other distros might
provide something else. If the file doesn't exist, then sensible defaults
are used. I hope a similar approach can be used to factor out any other
distro-specific rules that might be needed.
Comments etc very welcome,
Thanks,
NeilBrown
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