Re: [Xen-users] How do I resize a Physical Partition in a Dom U that's "on" a Logical Volume in the Dom 0?

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

Bob Linkonij wrote:

>  > I'm not clear here - did you partition /dev/xvdc and create a filesystem on
> >  /dev/xvdc1, or did you create a filesystem on /dev/xvdc ?
> I'm pretty foggy about the xvdc vs xvdc1 name differences but if I
> understand what you're asking I did the first type.  I'm not even sure
> how I'd do the latter, or if I should.
What does it say in /etc/fstab ?

If it has "/dev/xvdc" then the filesystem has been created in the 
whole disk, which I think is easiest.
If it has "/dev/xvdc1" then the virtual disk has been partitioned and 
the filesystem created inside the partition. How you would do that is 
you would simply treat the virtual disk the same way as a real disk 
and just partition it - from inside the guest.
> Anyway I used Suse SLED v10's auto-installation stuff to do it. The
> part of the script for the xvdc device was
>
> <partitioning config:type="list"><drive>
> <device>/dev/xvdc</device>
> <initialize config:type="boolean">false</initialize>
> <partitions config:type="list"><partition>
>  <create config:type="boolean">false</create>
>  <filesystem config:type="symbol">ext3</filesystem>
>  <format config:type="boolean">true</format>
>  <label>GUESTROOT</label>
>  <mount>/</mount>
>  <partition_id config:type="integer">131</partition_id>
>  <partition_nr config:type="integer">1</partition_nr>
>  <partition_type>primary</partition_type>
>  <size>max</size>
> </partition></partitions>
> <type config:type="symbol">CT_DISK</type>
> <use>all</use>
> </drive></partitioning>
Double dutch to me, but it does hint at having created a partition.

> >  If you create a filesystem on the disk device rather than partitioning it,
> >  then you can shutdown the guest, use resize2fs to enlarge the filesystem in
> >  it, and startup the guest.
> >
> >  If you created a partition, then you will need to deal with that. I think
> >  there was a discussion a while back on mounting partitions from a partition.
> >  You'll need to enlarge the partition to fill the disk, and then you can
> >  resize the filesystem in it. Other than doing it from within the guest I
> >  don't know how to do that. Once you shutdown and then start up (NOT reboot)
> >  the guest, it will see the new logical volume as a bigger disk - I don't
> >  know if there is any way to make this happen 'live'.
> So it sounds like the 1st one is simpler.  And can be done live or hot.
Actually, it can't be done live - you have to unmount the filesystem 
and fsck it before you can resize it. You'll struggle to unmount your 
root filesystem.
If you find that your root partition is /dev/xvdc1 then what I'd 
suggest is this :
shutdown the guest
boot up another guest with this LV attached as a disk. This can be an 
entirely different guest setup, or you could boot your current setup 
from one of the "live cd" distros such as Knoppix.
You'll now be able to use fdisk to alter the partition - so you'll do 
"fdisk /dev/xvdx" (where x is the current drive letter the LV gets 
mapped to). I can't remember the commands, but there is one to alter 
a partition, and you need to change the end of partition 1 (which 
should be the only one) to be the end of the disk.
use resize2fs to expand the filesystem to fill the partition.
shutdown the guest, return everything to normal, boot up your guest 
with the resized disk.
It's a lot easier to not use partitions in the guest. If you are 
happy doing that, you could consider re-installing without using 
partitions, but you may find it hard to persuade the installer to 
accept that. IIRC, in Debian (whose installer I was using only today) 
there isn't an option - but there may be a command line method to 
bypass the disk partitions step.
For Xen guests, I usually just clone a basic image that was created 
initially with debbootstrap - so I never use OS installers in a guest.
> Maybe I should just redo the whole thing to use the "create a
> filesystem on /dev/xvdc" way.
>
> Any pointers on that one?  I've tried to follow some of those
> discussions, and just get lost.  It seems like each message answers a
> question someone's not asking.
That's often the way.

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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