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Bug 166975 - snapshot gets conflicting device number at reboot
snapshot gets conflicting device number at reboot
Status: CLOSED DUPLICATE of bug 164959
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: lvm2 (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Alasdair Kergon
Depends On:
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Reported: 2005-08-29 06:52 EDT by Olle Liljenzin
Modified: 2007-11-30 17:07 EST (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2005-09-21 15:58:59 EDT
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Description Olle Liljenzin 2005-08-29 06:52:42 EDT
From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)

Description of problem:
Snapshot volumes get device numbers at boot that may conflict with persistent numbers used by other volumes. This may cause the system to hang.

In case a volume with conflicting number is present in fstab, you will get a chance to sort thing out when the filesystem check complaines about missing super block. If not in fstab, you will have use for the rescue disk to get back.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.Make the current device number persistent for an existing volume
E.g. 'lvdisplay /dev/VGSYS/foo' outputs 'Block device 253:7'
Run the commands:
% umount /dev/VGSYS/foo
% lvchange -M y --major 253 --minor 7 /dev/VGSYS/foo

2. Create a snapshot
% lvcreate -s -L 32M -n foo_snap /dev/VGSYS/foo

3. Reboot

Actual Results:  The machine will hang during boot because of conflicting device numbers

Expected Results:  The snapshot should get an unused device number

Additional info:
Comment 1 Olle Liljenzin 2005-08-29 14:37:25 EDT
This bug would be less urgent if bug 166750 was fixed.
Comment 3 Olle Liljenzin 2005-08-30 12:50:34 EDT
Decreasing severity since bug 166750 was closed.

Still a bug though.
Comment 4 Alasdair Kergon 2005-08-30 14:29:37 EDT
See 166750 for how to avoid this.

I can't think of anything the tools could do differently that would help.

An option to drop the persistent device number if it was not available.  That
would be tricky to code and I doubt it's worth the effort.

Perhaps a warning message if you set a persistent minor number smaller than the
number of LVs on your system?
Comment 5 Alasdair Kergon 2005-09-21 15:58:59 EDT
Not going to anything about this directly, but the proposed enhancements to
snapshots should stop the system hanging if a snapshot can't be activated.

*** This bug has been marked as a duplicate of 164959 ***

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