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

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Sat, May 15, 2010 at 01:29:13PM +0800, lei yang wrote:
>    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
>

If using a pvops domU kernel then you shouldn't use sd* for the guest disk.
pvops kernels only support xvd* as a guest disk.


>     and run
>    [1]root@intel_5500_server:/root> service xend start &
>    [1] 2114
>    [2]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.

Have you read:
http://wiki.xensource.com/xenwiki/XenParavirtOps

Especially the troubleshooting sections? 


>    [   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
>    [3]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?
> 

The image file is empty, so it doesn't contain a filesystem that could be 
mounted in the guest.
You need to actually *INSTALL* a guest to the image file.

-- Pasi

>    Thanks
>    Lei
> 
> 
> 
> 
> 
> 
>    On Sat, May 15, 2010 at 2:35 AM, Pasi Kärkkäinen <[4]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:[5]pasik@xxxxxx
> 
>    --
>    "We learn from failure, not from success!"
> 
> References
> 
>    Visible links
>    1. mailto:root@intel_5500_server/root
>    2. mailto:root@intel_5500_server/root
>    3. mailto:root@intel_5500_server/root
>    4. mailto:pasik@xxxxxx
>    5. mailto:pasik@xxxxxx

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