make recovery with non-existing device names in fstab

[Wouter Jagers]

Hi all,

Imagine a machine which, in case of disaster, takes over a bunch of disks and volume groups from (an)other machine(s) using EMC's SRDF functionality.

(it's a tad more complicated, with dual ServiceGuard clusters and all that, but that's not relevant to this particular problem)

As a result, some VG/LV device files are only present in a failover situation.

During such a failover, however, we need our backup system to back up these production filesystems. Since the backup system relies on fstab for this, we have added these (usually non-existing) filesystems to fstab, using the 'noauto' option to prevent mount-attempts in a normal situation.

Hence, we now have an fstab which contains 'noauto' entries for some devices which, when all is well, do not exist.

So far so good.. until we try an ignite backup: ignite cannot stat these device files, so it spawns an error and quits (as described in http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=11618 and http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1042482 )

These devices/filesystems are irrelevant to the ignite backup itself, but it seems like ignite really needs to find each and every device file mentioned in fstab before it will start creating an image..

The question: does anyone know of a way to tell ignite (C.6.1.44) to 'ignore' these non-existing device names in fstab ? Or am I being too optimistic here ;-)

Cheers,
Wout

[Tim Nelson]

Take a read through the man pages for make_net_recovery. -x can be used to ignore specific filesystems.


-x exclude=file|directory
Excludes the file or directory from the archive. When a
directory is specified, no files beneath that directory will
be stored in the archive. If the excluded directory is an
unmounted file system shown in the /etc/fstab file, a
WARNING ("Filesystem xxx is not mounted. It will be
ignored.") message will be displayed.

[Patrick Wallek]

There is no way I know of to tell Ignite to ignore your non-existent devices / filesystem in fstab.

Something that may work for you though is to create a "dummy" /etc/fstab that has only existing device files in it. As part of your Ignite backup script you could copy the "dummy" fstab (after making a backup of the "real" one), run the make_tape_recovery, then copy the "real" fstab back.

[Wouter Jagers]

Thanks for the replies.

Sadly enough that option doesn't apply here, Tim. These filesystems wouldn't be included in the first place, the problem is that ignite seems to consider these as 'impossible filesystems' rather than 'unmounted filesystems' (the device files aren't there), and worth an error.

I'd be happy if it would just ignore these fstab entries with a warning as well.

The second fstab file is a logical option, which I was initially trying to avoid: the extra entries in fstab were put there to prevent the need for such a second file when failing over.

However, in this case, we wouldn't need to maintain two separate fstab files (error prone), but the ignite script can create one on the fly, just removing all failover filesystems temporarily. That I could probably live with.

Thanks for the input !

Cheers,
Wout

[Bill Hassell]

This is a common complaint about the MTR/MNR programs. The code is trying to be helpful in pointing out that fstab has things that aren't mounted or don't exist. The noauto option is ignored by Ignite tools. I use noauto for /cdrom and it causes Ignite to fail or to report warnings. The only workaround for now is the temporary fstab file while MTR or MNR are running. It is very unlikely you'll need these entries in fstab for other tasks during the backup. It is a particularly challenging task to get a clean MTR/MNR so you can script the task and report success versus warnings versus failures.

[Sameer_Nirmal]

There is no way to ignore those non-existing device names in fstab. The recovery process will check every entry in the /etc/fstab file. Now knowing that entries commented with "#" in the /etc/fstab would end up with a warning message while running recovery process and recovery archive is created, one can put a script to put "#" in front of those non-existing device names in the fstab ( with a backup) before running a recovery process. The script should check the existance of the devices before putting "#" though.

Ideally, I do think that as long as you are not including a vg/directory in the archives related to those entries, the recovery process should flash a warning and should create an archive with devices included.

[Wouter Jagers]

Thanks guys.

So we've established that this is 'expected' behaviour and there's no way around it from within the tools.

We will craft a workaround.

Thanks again,
Cheers,
Wout

[Wouter Jagers]

Just for info, here's what has changed in our scripts:

Before the actual MNR:
---
cp /etc/fstab /etc/fstab.ign && sed '/^#IGNITE#/ !{
/noauto/s/^/#IGNITE#/
}' /etc/fstab.ign > /etc/fstab
---

After completion:
---
cp /etc/fstab /etc/fstab.ign && sed 's/^#IGNITE#//' /etc/fstab.ign > /etc/fstab
---

Cheers,
Wout