[Xen-users] Re: How to kown the DomU is up

[lei yang <yanglei.fage@xxxxxxxxx>]

Hi Pasi,

 

I find some of my concept is not clear.

 

After I boot domU, my domU root=/dev/sda1, I just have one hard disk and just one partition-->sda1

 and run

root@intel_5500_server:/root> service xend start &
[1] 2114
root@intel_5500_server:/root> mount: xenfs already mounted or /proc/xen busy
mount: according to mtab, none is already mounted on /proc/xen
Nothing to flush.
[   86.292484] xenbus_probe wake_waiting
[   86.296663] xenbus_probe wake_waiting
Traceback (most [   86.301310] XENBUS: Unable to read cpu state
recent call last[   86.307501] XENBUS: Unable to read cpu state
):
  File "/usr[   86.313693] XENBUS: Unable to read cpu state
/sbin/xend", lin[   86.320070] XENBUS: Unable to read cpu state
e 158, in <modul[   86.326362] XENBUS: Unable to read cpu state
e>
    sys.exit[   86.332740] XENBUS: Unable to read cpu state
(main())
  File[   86.339068] XENBUS: Unable to read cpu state
 "/usr/sbin/xend[   86.345378] XENBUS: Unable to read cpu state
", line 133, in [   86.351797] xenbus_probe_devices backend
main
    start_[   86.358882] xenbus_probe_devices failed xenbus_directory
[   86.364819] backend_probe_and_watch devices probed ok
blktapctrl()
  [   86.370770] backend_probe_and_watch watch add ok ok
[   86.377463] backend_probe_and_watch all done
[   86.382232] xenbus_probe_devices device
File "/usr/sbin/[   86.386832] xenbus_probe_devices failed xenbus_directory
[   86.394018] frontend_probe_and_watch devices probed ok
xend", line 108,[   86.400078] frontend_probe_and_watch watch add ok ok
[   86.406862] frontend_probe_and_watch all done
 in start_blktapctrl
    start_daemon("blktapctrl", "")
  File "/usr/sbin/xend", line 74, in start_daemon
    os.execvp(daemon, (daemon,) + args)
  File "/usr/lib/python2.5/os.py", line 354, in execvp
    _execvpe(file, args)
  File "/usr/lib/python2.5/os.py", line 392, in _execvpe
    func(fullname, *argrest)
OSError: [Errno 2] No such file or directory
root@intel_5500_server:/root>

I got above error, I don't know what cause it.

 then I find I don't have /dev/xvda in Dom0,

so I create it with

 

mknod /dev/xvda b 202 0
mknod /dev/xvda1 b 202 1

 

in dom0, question: do I need to create it in dom0? if not, where it can be create?

 

Then I create a image " dd if=/dev/zero of=domU.image bs=1M count=1000"

 

 

and my domU cfg file is

 

disk = ['file:/domU.image,xvda1,w']
kernel = "/vmlinuz-2.6.31.13"
vcpus=2
extra = "3 selinux=0 enforcing=0"
root = "/dev/xvda1 ro"        

 

(if I don't create /dev/xvda1 in dom0, it will tell me no /dev/xvda1 device)

does this file miss something?

 

I don't use initrd file for dom0 or domU, does it need for me?

 

then I boot domU with

xm create -f xx.cfg -c,

I got

 

[    0.266829] List of all partitions:
[    0.266841] ca01         1024000 xvda1 driver: vbd
[    0.266849] No filesystem could mount root, tried:  ext3 vfat msdos iso9660
[    0.266868] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(202,1)
[    0.266879] Pid: 1, comm: swapper Not tainted 2.6.31.13 #1

 

any idea?

 

Thanks

Lei

 

 

 

 

 

 

On Sat, May 15, 2010 at 2:35 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:

On Sat, May 15, 2010 at 02:00:10AM +0800, lei yang wrote:
>
>      I'm confused.. Are you trying to use the _same_ disk for the guest as
>      you use for dom0?
>      You can't do that.
>
>
>    my dom0 use /dev/sda1, can I use domU with  second partition /dev/sda2(may
>    be it correspond xvda2?)
>

Yes you can.

Or you can use a file in dom0 filesystem. Or you can create LVM volumegroup
and create an LVM volume for the guest.

>    if I can't use the second partition, hown do I use "an image file" , how
>    to produce a image file, and can I put it in /dev/sda1 to use
>

You can create an empty image file with "dd", for example, or with any another
normal unix/linux tool.

Usually the tool you use to install the guest OS can make guest image files for you.

>    Actually, I don't know what does mean by "disk = ['phy:/dev/sda,xvda,w' ]"
>    can you explan it for me
>

It means use xen "phy:" driver for the guest virtual disk, which requires you to
specify a 'physical' block device in dom0. The block device in question is "/dev/sda",
and it's mapped to be "/dev/xvda" in the guest. "w" means it's in read/write mode.

Another options is to use "file:" driver, which enables you to use image files instead of block devices.

>    does virtual disk use the phy disk space in fact?
>

Depends how you set it up.

Also I recommend you to start the guest with "xm create -f /etc/xen/<guest> -c",
which opens up the guest terminal immediately and allows you to see the
guest kernel boot process with all the messages.

-- Pasi

>    Thanks
>    Lei
>
>      You need to have another disk for the guest, or an image file, or lvm
>      volume..
>      >    4. I create the device by
>      >    mknod /dev/xvda b 202 0
>      >    mknod /dev/xvda1 b 202 1
>      >    when I mount -t ext3 /dev/xvda /
>      >
>      >    [5]root@intel_5500_server:/> mount -t ext3 /dev/xvda /
>      >    mount: /dev/xvda is not a valid block device
>      >    does it mean my xvda device driver is not loaded
>      >
>
>      xvda is the device name in the *guest*, which means the guest kernel
>      will see the virtual disk as /dev/xvda.
>      -- Pasi
>
>    --
>    "We learn from failure, not from success!"
>

> References
>
>    Visible links
>    1. mailto:pasik@xxxxxx

-- 
"We learn from failure, not from success!"
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