Re: [Xen-users] what's correct way of shrinking LVM based domU?

[Rudi Ahlers <Rudi@xxxxxxxxxxx>]

John Haxby wrote:
> Rudi Ahlers wrote:
> > Hi all
> >
> > I want to shrink one of my LVM based domU's, but don't quite know how 
> > to do it.
> > I have searched the Wiki  & HOWTO's, and they all show you how expand 
> > / enlarge a LVM based domU, but not shrinking it.
> It's the opposite, literally, of growing.
> > So, I stopped (destroyed) the domU, and then resized it as follows: 
> > lvresize /dev/data/cpanel1 -L10GB (It was 100GB), but when I a 
> > started it up again, I got some errors about the the disk being 
> > corrupt, and then a kernel panic.
> Looks like you missed out a vital step: you shrunk the logical volume 
> without first shrinking the file system within it.  Note that while 
> you can often grow a file system while it is on-line you almost always 
> need the file system off-line in order to shrink it.
> In this case, you need to shrink the file system, logical volume (if 
> any), physical volume (if any) and partition in the guest OS _before_ 
> you shrink the logical volume that contains them all in dom0.  Of 
> course, you can do all this from dom0 because the file system(s) 
> contain in the logical volume are all off-line.
> jch
ok, I don't know LVM at all. This is all a trail and error thing, since 
my previous installations have been image based and is difficult to resize.
So, what you're saying is that I should do this from the domU itself? 
But that then means it need to be running?
This is what I have:

[root@cPanel002 ~]# [root@HF-LINSRV01 ~]# lvscan
 ACTIVE            '/dev/data/cpanel002' [100.00 GB] inherit
 ACTIVE            '/dev/data/windows2003_web' [30.00 GB] inherit
 ACTIVE            '/dev/data/storage' [50.00 GB] inherit
 ACTIVE            '/dev/data/cacti' [20.00 GB] inherit
 ACTIVE            '/dev/data/cpanel2' [30.00 GB] inherit
 ACTIVE            '/dev/system/root' [39.06 GB] inherit
 ACTIVE            '/dev/system/swap' [9.75 GB] inherit


I need to resize the 100GB /dev/data/cpanel002

Do I enter the domU, and then resize it's partition first?

[root@HF-LINSRV01 ~]# xm console cPanel002
lvscan
 ACTIVE            '/dev/VolGroup00/LogVol00' [95.59 GB] inherit
 ACTIVE            '/dev/VolGroup00/LogVol01' [1.94 GB] inherit


Does this look right?

[root@cPanel002 ~]# lvresize /dev/VolGroup00/LogVol00  -L -80GB
 WARNING: Reducing active and open logical volume to 15.59 GB
 THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LogVol00? [y/n]:

I somehow don't trust this....



--

Kind Regards
Rudi Ahlers
CEO, SoftDux

Web:   http://www.SoftDux.com
Check out my technical blog, http://blog.softdux.com for Linux or other 
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