[linux-lvm] Question re: deleting an LV...

[Tanstaafl]

Hello,

Due to a misunderstanding about how LVM snapshots work when I set up
this system, I now need to delete an LV I had created to use for this
purpose (I thought I had to pre-create the LV).

Currently I have:

# lvscan
ACTIVE '/dev/vg/tmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/log' [5.00 GiB] inherit
ACTIVE '/dev/vg/vtmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/var' [700.00 GiB] inherit
ACTIVE '/dev/vg/snaps' [4.00 GiB] inherit

I just need to delete the /dev/vg/snaps LV, so that that 4GB is
available for my LVM snapshots.

Am I correct that all I have to do is:

# umount /dev/vg/snaps
# lvremove /dev/vg/snaps

Then remove this line from fstab?

This would then result in my VG having 4GB available for taking LVM
snapshots?

Thanks

[Tanstaafl]

Post by Tanstaafl
Hello,
Due to a misunderstanding about how LVM snapshots work when I set up
this system, I now need to delete an LV I had created to use for this
purpose (I thought I had to pre-create the LV).
# lvscan
ACTIVE '/dev/vg/tmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/log' [5.00 GiB] inherit
ACTIVE '/dev/vg/vtmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/var' [700.00 GiB] inherit
ACTIVE '/dev/vg/snaps' [4.00 GiB] inherit
I just need to delete the /dev/vg/snaps LV, so that that 4GB is
available for my LVM snapshots.
# umount /dev/vg/snaps
# lvremove /dev/vg/snaps
Then remove this line from fstab?
This would then result in my VG having 4GB available for taking LVM
snapshots?

Would appreciate a confirmation that I don't have to do anything else to
totally eliminate the snaps LV...

I unmounted it, and commented that line in fstab. lvscan still shows the
same as above, but lvs shows the snaps with a slightly different attribute:

# lvs
LV VG Attr LSize
log vg -wi-ao---- 5.00g
snaps vg -wi-a----- 4.00g
tmp vg -wi-ao---- 5.00g
var vg -wi-ao---- 700.00g
vtmp vg -wi-ao---- 5.00g

So again - is lvremove /dev/vg/snaps the correct way - and the only
thing I need to do - to remove that LV as if it had never been created?

Thanks

[Guy Rouillier]

Post by Tanstaafl

Post by Tanstaafl
Hello,
Due to a misunderstanding about how LVM snapshots work when I set up
this system, I now need to delete an LV I had created to use for this
purpose (I thought I had to pre-create the LV).
# lvscan
ACTIVE '/dev/vg/tmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/log' [5.00 GiB] inherit
ACTIVE '/dev/vg/vtmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/var' [700.00 GiB] inherit
ACTIVE '/dev/vg/snaps' [4.00 GiB] inherit
I just need to delete the /dev/vg/snaps LV, so that that 4GB is
available for my LVM snapshots.
# umount /dev/vg/snaps
# lvremove /dev/vg/snaps
Then remove this line from fstab?
This would then result in my VG having 4GB available for taking LVM
snapshots?

Would appreciate a confirmation that I don't have to do anything else to
totally eliminate the snaps LV...
I unmounted it, and commented that line in fstab. lvscan still shows the
# lvs
LV VG Attr LSize
log vg -wi-ao---- 5.00g
snaps vg -wi-a----- 4.00g
tmp vg -wi-ao---- 5.00g
var vg -wi-ao---- 700.00g
vtmp vg -wi-ao---- 5.00g
So again - is lvremove /dev/vg/snaps the correct way - and the only
thing I need to do - to remove that LV as if it had never been created?

Yes. This page has a definition of the attributes:
http://man7.org/linux/man-pages/man8/lvs.8.html. "o" in position 6
means device open; since you've unmounted it, it is no longer open.

I learned via this mailing list that lvremove just updates metadata to
make the space available again, but doesn't remove the filesystem in the
LV. So if you were to recreate the exact same LV you just removed, the
filesystem would still be there. My situation was unusual, and you
probably won't encounter this. But if you want to avoid that minor
possibility, use "wipefs -a /dev/vg/snaps" before lvremove.

[Tanstaafl]

Post by Guy Rouillier
I learned via this mailing list that lvremove just updates metadata to
make the space available again, but doesn't remove the filesystem in the
LV. So if you were to recreate the exact same LV you just removed, the
filesystem would still be there. My situation was unusual, and you
probably won't encounter this. But if you want to avoid that minor
possibility, use "wipefs -a /dev/vg/snaps" before lvremove.

Thanks for the reply Guy...

I don't think this is necessary, as this space

a) never had anything written to it, and

b) will be used for LVM snapshots, so even if it had, it would get
overwritten very soon.

Anyway, thanks... looking forward to getting my email rsnapshot backups
working using LVM snapshots (for consistency - no more 'file vanished'
messages during backups)...

Thx again

Charles

[Mauricio Tavares]

Post by Tanstaafl

Post by Tanstaafl
Hello,
Due to a misunderstanding about how LVM snapshots work when I set up
this system, I now need to delete an LV I had created to use for this
purpose (I thought I had to pre-create the LV).
# lvscan
ACTIVE '/dev/vg/tmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/log' [5.00 GiB] inherit
ACTIVE '/dev/vg/vtmp' [5.00 GiB] inherit
ACTIVE '/dev/vg/var' [700.00 GiB] inherit
ACTIVE '/dev/vg/snaps' [4.00 GiB] inherit
I just need to delete the /dev/vg/snaps LV, so that that 4GB is
available for my LVM snapshots.
# umount /dev/vg/snaps
# lvremove /dev/vg/snaps
Then remove this line from fstab?
This would then result in my VG having 4GB available for taking LVM
snapshots?

Would appreciate a confirmation that I don't have to do anything else to
totally eliminate the snaps LV...
I unmounted it, and commented that line in fstab. lvscan still shows the
# lvs
LV VG Attr LSize
log vg -wi-ao---- 5.00g
snaps vg -wi-a----- 4.00g
tmp vg -wi-ao---- 5.00g
var vg -wi-ao---- 700.00g
vtmp vg -wi-ao---- 5.00g
So again - is lvremove /dev/vg/snaps the correct way - and the only
thing I need to do - to remove that LV as if it had never been created?

http://man7.org/linux/man-pages/man8/lvs.8.html. "o" in position 6 means
device open; since you've unmounted it, it is no longer open.
I learned via this mailing list that lvremove just updates metadata to make
the space available again, but doesn't remove the filesystem in the LV. So
if you were to recreate the exact same LV you just removed, the filesystem
would still be there. My situation was unusual, and you probably won't
encounter this. But if you want to avoid that minor possibility, use
"wipefs -a /dev/vg/snaps" before lvremove.

Going a bit on a tangent, thanks for the info. I need to add
that to my notes because sometimes when I want a lv to go away, I
really really want it to go

--
Guy Rouillier
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