LVM Object Tags

An LVM tag is a word that can be used to group LVM2 objects of the same type together. Tags can be attached to objects such as physical volumes, volume groups, and logical volumes. Tags can be attached to hosts in a cluster configuration. Snapshots cannot be tagged.

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.

As of the Red Hat Enterprise Linux 6.1 release, LVM tags are strings of up to 1024 characters (for earlier releases the upper length limit was 128 characters). LVM tags cannot start with a hyphen.

A valid tag can consist of a limited range of characters only. For the Red Hat Enterprise Linux 6.0 release, the allowed characters are [A-Za-z0-9_+.-]. As of the Red Hat Enterprise Linux 6.1 release, the list of allowed characters has been extended, and tags can contain the "/", "=", "!", ":", "#", and "&" characters.

Only objects in a volume group can be tagged. Physical volumes lose their tags if they are removed from a volume group; this is because tags are stored as part of the volume group metadata and that is deleted when a physical volume is removed. Snapshots cannot be tagged.

The following command lists all the logical volumes with the database tag.

lvs @database

C.1. Adding and Removing Object Tags

To add or delete tags from physical volumes, use the --addtag or --deltag option of the pvchange command.

To add or delete tags from volume groups, use the --addtag or --deltag option of the vgchange or vgcreate commands.

To add or delete tags from logical volumes, use the --addtag or --deltag option of the lvchange or lvcreate commands.

As of the Red Hat Enterprise Linux 6.1 release, you can specify multiple --addtag and --deltag arguments within a single pvchange, vgchange, or lvchange command. For example, the following command deletes the tags T9 and T10 and adds the tags T13 and T14 to the volume group grant.

vgchange --deltag T9 --deltag T10 --addtag T13 --addtag T14 grant