RE: [Xen-users] xen kernel can't boot up! it say: VFS: Cannot open root device "sda4" or unknown-block(0,0)

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of youhongyu
> Sent: 29 May 2007 17:35
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] xen kernel can't boot up! it say: VFS: 
> Cannot open root device "sda4" or unknown-block(0,0)
> 
> 
> hi all,
> 
> I am really need help!
> My case: fedora 3, hdc1 is /boot, hdc2 is swap, hdc3 is / .
> I download xen barball and follow the README in it to 
> compile, but when I
> turn to boot xen-kernel, I got this:
>   VFS: Cannot open root device "sda4" or unknown-block(0,0)
>   Please append a correct "root=" boot option

Natural, if you don't have a "/dev/sda4" in the first place...  

> or
>   VFS: Cannot open root device "/dev/hdc3" or unknown-block(0,0)
>   Please append a correct "root=" boot option

Most likely because you don't have a (correct) initrd file. 

"mkinitrd /boot/<something> 2.6.18-xen" or something similar should work
here. 

> or
>   VFS: Cannot open root device "LABEL=/" or unknown-block(0,0)
>   Please append a correct "root=" boot option

I'm sure "LABEL" can be made to work, but if you know which disk is your
root disk, it works just as well to give it "/dev/hdc3" or some such -
it really is just a way to link the device and to a "name". 


> why? and i am also wonder why install program will give 
> /dev/sda4 to my
> grub? 

Because it's stupid??? What install program did you use?


> Following may be needed to spot my fault. Can anybody help 
> me? I had stop at
> here for a few days!
> thanks very much.

Perhaps the next problem is that the install program built a initrd
based on you having a "scsi" type disk to boot from? Try using
"mkinitrd" manuallay as above. 

--
Mats
> 
> youhongyu
> 
> --------------------------------------------------------------
> 
> [root@localhost xen-install]# fdisk -l
> 
> Disk /dev/hdc: 80.0 GB, 80026361856 bytes
> 255 heads, 63 sectors/track, 9729 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/hdc1   *           1          13      104391   83  Linux
> /dev/hdc2              14         144     1052257+  82  Linux swap
> /dev/hdc3             145        9729    76991512+  83  Linux
> 
> --------------------------------------------------------------
> 
> [root@localhost xen-install]# df -lh
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/hdc3              73G  4.4G   65G   7% /
> /dev/hdc1              99M   29M   65M  31% /boot
> none                  249M     0  249M   0% /dev/shm
> 
> --------------------------------------------------------------
> 
> [root@localhost xen-install]# cat /proc/partitions 
> major minor  #blocks  name
> 
>   22     0   78150744 hdc
>   22     1     104391 hdc1
>   22     2    1052257 hdc2
>   22     3   76991512 hdc3
>   
> --------------------------------------------------------------
> [root@localhost xen-install]# cat /etc/fstab
> # This file is edited by fstab-sync - see 'man fstab-sync' for details
> #/dev/hdc3                 /                       ext3    
> defaults        1
> 1
> LABEL=/                 /                       ext3    
> defaults        1 1
> #/dev/hdc1             /boot                   ext3    
> defaults        1 2
> LABEL=/boot             /boot                   ext3    
> defaults        1 2
> none                    /dev/pts                devpts  
> gid=5,mode=620  0 0
> none                    /dev/shm                tmpfs   
> defaults        0 0
> none                    /proc                   proc    
> defaults        0 0
> none                    /sys                    sysfs   
> defaults        0 0
> #/dev/hdc2         swap                    swap    defaults        0 0
> LABEL=SWAP-hdc2         swap                    swap    
> defaults        0 0
> /dev/hdd                /media/cdrom            auto   
> pamconsole,ro,exec,noauto,managed 0 0
>   
> --------------------------------------------------------------
> 
> /boot/grub/grub.conf:
> default=0
> timeout=8
> splashimage=(hd0,0)/grub/splash.xpm.gz
> hiddenmenu
> title Fedora Core (2.6.9-1.667)
>         root (hd0,0)
>         kernel /vmlinuz-2.6.9-1.667 ro root=LABEL=/ rhgb quiet
>         initrd /initrd-2.6.9-1.667.img
> 
> title Xen 3.0 / XenLinux 2.6
>         root (hd0,0)
>         kernel /xen-3.gz dom0_mem=262144
> #       module /vmlinuz-2.6-xen ro root=LABEL=/
> #       module /vmlinuz-2.6-xen root=/dev/sda4 ro console=tty0
>         module /vmlinuz-2.6-xen root=/dev/hdc3 ro console=tty0
>         module /xen.new.img
> --------------------------------------------------------------
> 
> -- 
> View this message in context: 
> http://www.nabble.com/xen-kernel-can%27t-boot-up%21-it-say%3A-
> VFS%3A-Cannot-open-root-device-%22sda4%22-or-unknown-block%280
> %2C0%29-tf3835072.html#a10857713
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> 
> 
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