[linux-lvm] shrink pv without pvresize (FC3 LVM)

[linux-lvm] shrink pv without pvresize (FC3 LVM)

[Ilya Goldin]

I did something stupid, and I need help.

The goal is to have a single hard drive with four partitions: NTFS,
FAT32 (/home), swap, and LVM ext3 (/). What I have now is NTFS, Swap,
and one LVM VG that contains both / and /home, and both are ext3.

First,

# pvresize
Command not implemented yet.

Is there a workaround (short of writing pvresize)?

Second, I had a feeble hope that Windows XP (booted off the NTFS
partition) would deign to see a FAT32 LV under LVM. That is, if I change
/home to be FAT32, Windows might see it, so I figured I'd give it a
shot. (Is this futile?)

# mkdosfs -F 32 /dev/VolGroup00/LogVol02
mkdosfs 2.8 (28 Feb 2001)
mkdosfs: Unable to get drive geometry for '/dev/VolGroup00/LogVol02'

Why can't it get the geometry? Does LVM support FAT32 LVs? Does mkdosfs
support LVM?

Thanks!

Re: [linux-lvm] shrink pv without pvresize (FC3 LVM)

[Alasdair G Kergon]

On Fri, Dec 10, 2004 at 05:55:09PM -0500, Ilya Goldin wrote:
> # pvresize
 
> Is there a workaround (short of writing pvresize)?
 
Yes - vgcfgbackup, edit backup file, vgcfgrestore.

The field you need to edit to change the size is pe_count
according to:

  pe_start + pe_count * extent_size <= dev_size

i.e.
  pe_count <= (dev_size - pe_start) / extent_size

You can find out the current device size with:
  pvs -o +dev_size --units s

[The units used in the file are sectors of 512 bytes]

Only change pe_count for the PV you're resizing and nothing else!

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] shrink pv without pvresize (FC3 LVM)

[Alasdair G Kergon]

On Sun, Dec 12, 2004 at 05:24:29PM +0000, Alasdair G Kergon wrote:
> Only change pe_count for the PV you're resizing and nothing else!
 
And I forgot to say the obvious: if you're shrinking a PV, be sure
to pvmove any data off the part you're removing first:-)

If you've only one PV, you might need 'pvmove --alloc anywhere' to
do this.

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] shrink pv without pvresize (FC3 LVM)

[Alasdair G Kergon]

On Fri, Dec 10, 2004 at 05:55:09PM -0500, Ilya Goldin wrote:
> Why can't it get the geometry? Does LVM support FAT32 LVs? Does mkdosfs
> support LVM?
 
ioctl(3, HDIO_GETGEO, 0xbffffa8c)       = -1 ENOTTY (Inappropriate ioctl for device)

Something probably needs to make up a geometry.

Alasdair
-- 
agk@redhat.com