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Re: [Xen-users] xen kernel can't boot up! it say: VFS: Cannot open root

To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] xen kernel can't boot up! it say: VFS: Cannot open root device "sda4" or unknown-block(0, 0)
From: "youhongyu" <youhongyu@xxxxxxxxxxxxxxx>
Date: Wed, 30 May 2007 12:54:08 +0800
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thanks very much! finally i boot it up! 

I did following: 
    cd build-linux-2.6.18-xen_x86_32 
    make menuconfig 
    (add all module about ext3 and ide hdd....) 
    cd .. 
    make dist 
    ("make world" is bad, it will clear all .o and .ko, cost much time to 
compile) 
    make install 
    cd /lib/module 
    depmod 
    mkinitrd xen.new.img 2.6.18-xen 
    mv xen.new.img /boot 

my grub.conf: 
title Xen 3.0 / XenLinux 2.6 
         root (hd0,0) 
         kernel /xen-3.gz dom0_mem=262144 
         module /vmlinuz-2.6-xen root=/dev/hdc3 ro console=tty0 
         module /xen.new.img 

and reboot it. hope to be a hint to others who encounter the same problem. 

----- Original Message ----- 
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
To: "youhongyu" <youhongyu@xxxxxxxxxxxxxxx>; <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, May 30, 2007 12:42 AM
Subject: RE: [Xen-users] xen kernel can't boot up! it say: VFS: Cannot open 
root device "sda4" or unknown-block(0,0)




> -----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
> Sent from the Xen - User mailing list archive at Nabble.com.
> 
> 
> _______________________________________________
> Xen-users mailing list
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> 
> 
> 

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