Re: expanding virtual disk based on lvm

[Ross Boylan <ross@biostat.ucsf.edu>]

On Tue, 2012-08-28 at 14:15 -0700, Freddie Cash wrote:
> On Tue, Aug 28, 2012 at 1:26 PM, Ross Boylan <ross@biostat.ucsf.edu> wrote:
> > My vm launches with -hda /dev/turtle/VD0 -hdb /dev/turtle/VD1, where VD0
> > and VD1 are lvm logical volumes.  I used lvextend to expand them, but
> > the VM, started after the expansion, does not seem to see the extra
> > space.
> 
> You've increased the size of the hard drive, but you haven't changed
> the filesystem on top of the hard drive to use that extra space.
> 
> How you do that depends on whether the virtual disks are partitioned
> with filesystems in the partitions; or formatted with a filesystem
> directly.
The virtual disks are partitioned.
> 
> If they are partitioned, then you need to boot off a LiveCD, extend
> the partition, then extend the filesystem in the partition.
So I edit the parition table  directly?  I thought there might be some
meta-information that kvm used to establish the size of the physical
disk.

I'm not sure what the final sector number should be; I could get it
approximately from the size, but I'm not sure my calculation would be
just right.
> 
> If they are formatted directly, then (depending on the filesystem) you
> can grow the filesystem.  Some filesystems can't be extended live, so
> you have to boot to a LiveCD.
> 
> No fancy VM-related tools required.  Just think in terms of real,
> physical hardware, and it all becomes clear.  :)
My real physical disks have never grown spontaneously. :)  I also wasn't
sure how the kernel would react, and so I shut it down during the
growth.

Ross