[CentOS] LVM

David Goldsmith dgoldsmith at sans.org
Tue Mar 20 07:43:52 EDT 2012


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On 3/20/2012 5:25 AM, Markus Falb wrote:
> On 19.3.2012 10:14, Peter Kjellström wrote:
>> On Sunday 18 March 2012 19.40.21 Ray Van Dolson wrote:
>>> On Sun, Mar 18, 2012 at 08:04:14PM +0100, Markus Falb wrote:
> 
>>>> What filesystem? Assuming ext3, this cannot shrunk without
>>>> unmounting. I believe the following *should* work for ext3
>>>> 
>>>> $ umount /home $ e2fsck -f /dev/vg_web/lv_home $ resize2fs
>>>> /dev/vg_web/lv_home 150g $ lvresize -L 150g
>>>> /dev/vg_web/lv_home $ mount /home
>>>> 
>>>> I am not sure how safe it is. Take care!
> 
>> I'd like to add that it's probably good paranoia not to size the
>> lv down too tightly (should it happen to become smaller than the
>> fs then ooops). That is, I'd size the lv down to a comfortable
>> margin above the fs size (and then size the fs up to the device
>> size).
> 
> Hmm. I did that too a couple of times in the past. But why? What
> are the reasons for the paranoia?

I think he means don't resize/shrink the filesystem *and* the LVM LV
to the exact same size.  If the LVM lvresize command were to truncate
the end of the existing filesystem, now you have issues.

Instead do this: first shrink the filesystem a little smaller than you
want, then resize the LVM LV down to the desired size, then resize the
filesystem again to grow to use the remaining space.  This way you
ensure you don't snip of the end of the filesystem.

# umount /home
# e2fsck -f /dev/vg_web/lv_home
# resize2fs /dev/vg_web/lv_home 149g
# lvresize -L 150g /dev/vg_web/lv_home
# resize2fs /dev/vg_web/lv_home  (will default to the LV size of 150g)
# mount /home

- -- 
David Goldsmith
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