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LVM2 snapshots on root fs

linux-lvm Thomas Klaube 4 participants 4 messages Sep 7, 2004 – Sep 8, 2004

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Thomas Klaube

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Hi,

we are using lvm (lvm version 1) snapshots for backup purposes for some time without any problems.

Whenever I try to create a LVM (version 2) snapshot of the lvm containing the root fs my machine crashes. I am using SuSE 9.1 (kernel 2.6.5, lvm2-2.00.15, device-mapper-1.00.09), but I also tried a unpatched 2.6.8.1 kernel with the redhat lvm2-2.00.21 and device-mapper-1.00.19 rpms. Same result... I can't create snapshots of the lvm with the root fs, other lvm snapshots are ok.

Is this a known lvm2 problem? If it is a kernel issue, are there any patches?

Regards
Thomas Klaube

#1 lore raw
Quoted 2 lines · Thomas Klaube

Whenever I try to create a LVM (version 2) snapshot of the lvm containing the root fs my machine crashes. I am using SuSE 9.1 (kernel

We don't support pvmove or snapshots of volumes used by the tools themselves.

It is possible to snapshot the root volume, but the method is probably distribution-specific. Certain changes to the tools may make it easier to support: a general parameterised script might be possible.

Alasdair

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#2 lore raw
Quoted 2 lines · Alasdair G Kergon

We don't support pvmove or snapshots of volumes used by the tools themselves.

That seems rather limiting. Is this something that should change in the future?

Quoted 2 lines

It is possible to snapshot the root volume, but the method is probably distribution-specific.

Like what? Using a copy of the /sbin/lvm2 binary not living in the rootfs when you want to snapshot it? What about /lib/libdevmapper.so.*? Does it have the same problem?

b.

#3 lore raw
Quoted 8 lines · Brian J. Murrell
Quoted 2 lines · Alasdair G Kergon

It is possible to snapshot the root volume, but the method is probably distribution-specific.

Like what? Using a copy of the /sbin/lvm2 binary not living in the rootfs when you want to snapshot it? What about /lib/libdevmapper.so.*? Does it have the same problem?

Just copying /sbin/lvm2 to some other (non root) lvm does not do the job for me. Even if it worked it seems to be an ugly workaround.

The question is, if there are plans to change the snapshot capabilities of lvm2 in a way, that makes it possible to create snapshots even if the tools reside on the lvm.

Regards
Thomas Klaube