[linux-lvm] addtag
Clay Gerrard
clay.gerrard at gmail.com
Thu Apr 26 15:09:12 UTC 2012
On Ubuntu Oneiric the man page for lvm describes the use of tags, with
an addendum about tagging snapshots:
--addtag tag
Add the tag tag to a PV, VG or LV. A tag is a word that can be
used to group LVM2 objects of the same type together. Tags can
be given on the command line in place of PV, VG or LV arguments.
Tags should be prefixed with @ to avoid ambiguity. Each tag is
expanded by replacing it with all objects possessing that tag
which are of the type expected by its position on the command
line. PVs can only possess tags while they are part of a Volume
Group: PV tags are discarded if the PV is removed from the VG.
As an example, you could tag some LVs as database and others as
userdata and then activate the database ones with lvchange -ay
@database. Objects can possess multiple tags simultaneously.
Only the new LVM2 metadata format supports tagging: objects
using the LVM1 metadata format cannot be tagged because the on-
disk format does not support it. **Snapshots cannot
be tagged.**
Characters allowed in tags are: A-Z a-z 0-9 _ + . -
Specifically I'm concerned about "Snapshots cannot be tagged."
It seems that tagging of snapshots *is* supported?
root at myhost:~# lvcreate myvg -n vol1 -L 100M
Logical volume "vol1" created
root at myhost:~# lvcreate myvg/vol1 -s -n mysnap -L 100M
Logical volume "mysnap" created
root at myhost:~# lvchange --addtag mytag myvg/mysnap
Logical volume "mysnap" changed
root at myhost:~# lvs @mytag
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
mysnap myvg swi-a- 100.00m vol1 0.01
Can I rely on this feature being supported for snapshots despite the
man page's statement to the contrary?
Best Regards,
-clayg
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