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

[Mauricio Tavares]

On Mon, Jan 6, 2014 at 5:40 PM, Guy Rouillier <guy.rouillier at gmail.com> wrote:
> On 1/6/2014 7:59 AM, Tanstaafl wrote:
>>
>> On 2013-12-30 8:03 AM, Tanstaafl <tanstaafl at libertytrek.org> wrote:
>>>
>>> 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?
>>
>>
>> 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?
>
>
> 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.
>
      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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