[linux-lvm] vgscan fails to find volume groups

["Jason A. Fager" <jafager@jafager.com>]

I have been attempting to get LVM set up on a freshly-installed
Slackware 8.0 system (custom 2.4.18 monolithic kernel, LVM 1.0.3,
no kernel patches).  It works fine in multi-user mode, it works
fine in single-user mode, however I set up the single-user init
script like this:

(/ is mounted read only at this point)
mount -o remount,rw /
vgscan
vgchange -a y
mount -o remount,ro /
(stock Slackware fsck and mount bits)

The only volume group I have contains one physical volume
(/dev/sdb, on an Adaptec 7xxx controller).  For some reason,
vgscan doesn't pick up the volume group.  The exit code is 0,
and looking at the debug output it hits /dev/sdb and spits out
the same messages as when it hits all the other devices.

As an experiment I put a call to sulogin before the vgscan and
tried running it by hand; same thing happened.  I tried running
pvcreate (on the whole disk, and after creating an LVM partition
/dev/sdb1) and it failed with error code 7.

As another experiment, I tried setting up a loopback filesystem
on a file in the root directory.  That worked perfectly; vgscan
picked it up, vgchange activated it, and the rest of the init
script ran fsck and mounted it.  Other than setting up the
loopback file the only thing I did was add a call to losetup
before the vgscan.

Not sure if this is a problem with the kernel (i.e. SCSI driver)
or a problem with LVM, or some boneheaded thing I'm doing wrong.
Any advice you can give would be appreciated -- let me know if
I can provide more information.

thanks,
jafager