On Mon, Apr 07, 2014 at 03:10:14PM -0400, Vivek Goyal wrote: > On Mon, Apr 07, 2014 at 10:07:20PM +0400, Andrey Borzenkov wrote: > > В Mon, 7 Apr 2014 13:40:17 -0400 > > Vivek Goyal <vgo...@redhat.com> пишет: > > > > > > > > Defining a new target which by default waits for all the local fs target > > > sounds interesting. Again, I have the question, what will happen to > > > local-fs-all.target if some device does not show up and say one of the > > > mounts specified in /etc/fstab fails. It result is different for Requires= and for Wants=. Iff there's a chain of Requires= from the failing unit (.device in this case) to the target unit it will fail. Otherwise, it'll just be delayed. If, as I suggested above local-fs-all.target would have Requires= on the .mount units, then your unit could still have Wants=/After=local-fs-all.target, and it'll be started even if some mounts fail.
> > > What we want is. > > > > > > - Wait for all devices to show up as specified in /etc/fstab. Run fsck > > > on devices. Mount devices to mount points specified. > > > > > > - If everything is successful, things are fine and local-fs-all.target > > > will be reached. > > > > > > - If some device does not show up, or if fsck fails or mount fails, still > > > local-fs-all.target should reach so that kdump module can detect that > > > failure happened and can take alternative action. Alternatively, you can specify a soft depenendency on local-fs-all.target by using Wants=local-fs-all.target. I think this is preferable, because we want local-fs-all.target to be as similar as possible to local-fs.target, which has Requires= on the mount points. With this caveat, this should all be satisfied with my proposal. > > You can use OnFailure= to define unit(s) started when > > local-fs-all.target fails. But it sounds like you are not really > > interested in *all* filesystems, but in specific fileststems defined in > > kdump configuration. > > Kdump scripts registers with dracut as pre-pivot hook. And I believe > that in initramfs environments /etc/fstab does not contain all > filesystems. It prmarily contains root and any file system specified > on dracut command line using --mount option during initramfs generation. > > So my understanding that given the fact that /etc/fstab is minimal in > initramfs, we should be fine waiting for all the fs specified. > > Given the fact that we run under dracut pre-pivot hook callback, I think > dracut-pre-pivot.service wil have to create a dependency to run after > local-fs-all.target is reached. Hm, maybe. It would be good to get some input from Harald here. This is pretty specialized, so maybe it'd be better to have a separate unit positioned before or after or parallel to dracut-pre-pivot.service. > Now I am not sure who will generate local-fs-all.target. It would become a standard unit in systemd, like local-fs.target. Mount units would be added to this target by fstab-generator. > If dracut > generates it then dracut will also specify OnFailure=. Question will > still remain how dracut modules will communicate to dracut that what > to run after local-fs-all.target fails. > > In fact if dracut is doing all this, we don't have to create a separate > target. Right now we force "nofail" so that if mount fails, initrd.target > is still reached. > > If we can create a separate service to just handle failures, then we > probably should be able to spcify OnFailure=dracut-failure-hander.service > in right file and as modules to register their failure handler hooks > there. > > Something like create new hook called pre-pivot-failure and modules > register a hook to handle pre-pivot-failure. Then kdump can get the > control and handle failure. > > And this should allow dracut pre pivot service to specify to launch > dracut-failure-handler.service upon failure. > > > > > > For example, > > > > > > Asssume a user wants to save vmcore to nfs destination. Now for > > > whatever > > > reason, nfs target could not be mounted. In that case kdump will still > > > like to get control and alternatively save dump to local root fs. > > > > > > > Without knowing details it sounds like RequiresMountsFor is more > > appropriate (and can be set by generator based on actual kdump > > configuration). > > I am not sure how is it useful for this case. dracut already generates > all dependencies and puts them in /etc/fstab. And only entries in > /etc/fstab should be which dracut wants. So I guess we should be fine > and not need using RequiresMountsFor. Zbyszek _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
