LVM and loop device : Bad magic number

[Vincent Schultz]

Hello all,

I wanted to test LVM with loopdevice, but I experience some problems.
Here there are :

# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume
group
# dd if=/dev/zero of=/tmp/vdisk0 bs=50M count=1
# losetup /dev/loop0 /tmp/vdisk0

# pvcreate /dev/loop0
pvcreate -- physical volume "/dev/loop0" successfully created

# vgcreate VG_home /dev/loop0
vgcreate -- INFO: using default physical extent size 4 MB
vgcreate -- INFO: maximum logical volume size is 255.99 Gigabyte
vgcreate -- doing automatic backup of volume group "VG_home"
vgcreate -- volume group "VG_home" successfully created and activated

[root at satellite root]# lvcreate -L40M -n LV_admins VG_home
lvcreate -- doing automatic backup of "VG_home"
lvcreate -- logical volume "/dev/VG_home/LV_admins" successfully created

[root at satellite root]# mke2fs -j /dev/VG_home/LV_admins
mke2fs 1.34 (25-Jul-2003)
Filesystem label=
[...]
Writing inode tables: done
Creating journal (4096 blocks): done

[root at satellite root]# dumpe2fs /dev/VG_home/LV_admins
dumpe2fs 1.34 (25-Jul-2003)
dumpe2fs: Bad magic number in super-block while trying to open
/dev/VG_home/LV_admins
Couldn't find valid filesystem superblock.

Impossible to mount the FS too!

I am using a 2.4.22-1.2174.nptl on a Fedora Core 1.& lvm-1.0.3-13
=
I read that it should be a good idea to upgrade lvm, so I installed 
lvm-1.0.5-1.i386.rpm for Red Hat Contrib, but it still the same.

Do you have an idea ? Where I went wrong ?

Thanks for your help,

Vincent