Hi all!

Doing some tests with CentOS 5.5 on a KVM virtual machine, after doing the installation, I added a second disk. But when trying to boot from it, I get the following error:

--------------------------------------------------------------------- root (hd1,0)

Error 21: Selected disk does not exist ---------------------------------------------------------------------

The two disks are Virtio devices that are recognized when booting from the first disk:

--------------------------------------------------------------------- [root@localhost ~]# fdisk -l /dev/vda

Disco /dev/vda: 10.7 GB, 10737418240 bytes 255 heads, 63 sectors/track, 1305 cylinders Unidades = cilindros de 16065 * 512 = 8225280 bytes

Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/vda1 * 1 1174 9430123+ fd Linux raid autodetect /dev/vda2 1175 1305 1052257+ fd Linux raid autodetect [root@localhost ~]# [root@localhost ~]# [root@localhost ~]# fdisk -l /dev/vdb

Disco /dev/vdb: 10.7 GB, 10737418240 bytes 255 heads, 63 sectors/track, 1305 cylinders Unidades = cilindros de 16065 * 512 = 8225280 bytes

Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/vdb1 * 1 1174 9430123+ fd Linux raid autodetect /dev/vdb2 1175 1305 1052257+ fd Linux raid autodetect ---------------------------------------------------------------------

The idea of these tests is to set up software RAID1 on a running system, since, as I said in another thread, it seems that Anaconda does not support installation on degraded RAID.

But I'm not sure if this is a problem of Virtio or that GRUB is not recognizing the second disk.

I made sure to modify /boot/grub/device.map with the entry for the new disk:

--------------------------------------------------------------------- [root@localhost grub]# cat /boot/grub/device.map # this device map was generated by anaconda (hd0) /dev/vda (hd1) /dev/vdb ---------------------------------------------------------------------

And the reconfiguration of GRUB on both disks did not give problems:

--------------------------------------------------------------------- [root@localhost grub]# grub --device-map=/boot/grub/device.map

GNU GRUB version 0.97 (640K lower / 3072K upper memory)

[ Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists the possible completions of a device/filename.] grub> root (hd0,0) root (hd0,0) Filesystem type is ext2fs, partition type 0xfd grub> setup (hd0) setup (hd0) Checking if "/boot/grub/stage1" exists... yes Checking if "/boot/grub/stage2" exists... yes Checking if "/boot/grub/e2fs_stage1_5" exists... yes Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded. succeeded Running "install /boot/grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded Done. grub> root (hd1,0) root (hd1,0) Filesystem type is ext2fs, partition type 0xfd grub> setup (hd1) setup (hd1) Checking if "/boot/grub/stage1" exists... yes Checking if "/boot/grub/stage2" exists... yes Checking if "/boot/grub/e2fs_stage1_5" exists... yes Running "embed /boot/grub/e2fs_stage1_5 (hd1)"... 15 sectors are embedded. succeeded Running "install /boot/grub/stage1 (hd1) (hd1)1+15 p (hd1,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded Done. grub> quit quit ---------------------------------------------------------------------

Any idea what may be causing the problem?

Thanks in advance for your replies.

Regards, Daniel