[linux-lvm] Identifying useable block devices
Marius Vollmer
marius.vollmer at redhat.com
Wed Jan 15 08:19:33 UTC 2014
Hi,
when looking at the udev properties of a device mapper node, how can I
decide whether this is a block device that the user can use for creating
filesystems on, etc?
For example, when creating a thinly provisioned logical volume with these
steps
# vgcreate TEST /dev/loop1
# lvcreate TEST --thinpool pool -L 80
# lvcreate -T TEST/pool -n thin -V 100
I end up with a lot of devices:
# ls /dev/mapper/TEST-*
/dev/mapper/TEST-pool /dev/mapper/TEST-pool_tmeta /dev/mapper/TEST-thin
/dev/mapper/TEST-pool_tdata /dev/mapper/TEST-pool-tpool
How can a program tell that only /dev/mapper/TEST-thin can really be
used as a block device, and the rest should be ignored?
Is there a way to do this by looking at "udevadm info", for example?
(What seems to work is skipping all nodes that have
DM_UDEV_IGNORE_DISK_RULES_FLAG set to true. Is this maybe even
documented somewhere?)
Thanks!
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