~ # xm list
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0      491     2 r-----     44.1
dt1                                        1      256     1 -b----      0.1
~ # cat /etc/xen/fbsd1.cfg 
kernel = "/opt/kernel-current"
memory = 256
name = "freebsd"
vif = [ '' ]
disk = [ 'file:/opt/mdroot-7.0,hda1,w' ]
#on_crash    = 'preserve'
extra = "boot_verbose"
extra += ",boot_single"
extra += ",kern.hz=100"
extra += ",vfs.root.mountfrom=ufs:/dev/xbd769a"
~ # ls -l /opt/kernel-current 
-rwxr-xr-x 1 root root 2874166 Jun 22 01:56 /opt/kernel-current
~ # ls -l /opt/mdroot-7.0 
-rwxr-xr-x 1 root root 536870912 Jun 22 01:40 /opt/mdroot-7.0
~ # xm create /etc/xen/fbsd1.cfg -c
Using config file "/etc/xen/fbsd1.cfg".
Error: (22, 'Invalid argument')
~ # xm create /etc/xen/fbsd1.cfg   
Using config file "/etc/xen/fbsd1.cfg".
Error: (22, 'Invalid argument')

=====================================

[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) XendDomainInfo.create(['vm', ['name', 'freebsd'], ['memory', 256], ['vcpus', 1], ['image', ['linux', ['kernel', '/opt/kernel-current'], ['args', 'boot_verbose,boot_single,kern.hz=100,vfs.root.mountfrom=ufs:/dev/xbd769a']]], ['device', ['vbd', ['uname', 'file:/opt/mdroot-7.0'], ['dev', 'hda1'], ['mode', 'w']]], ['device', ['vif']]])
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) parseConfig: config is ['vm', ['name', 'freebsd'], ['memory', 256], ['vcpus', 1], ['image', ['linux', ['kernel', '/opt/kernel-current'], ['args', 'boot_verbose,boot_single,kern.hz=100,vfs.root.mountfrom=ufs:/dev/xbd769a']]], ['device', ['vbd', ['uname', 'file:/opt/mdroot-7.0'], ['dev', 'hda1'], ['mode', 'w']]], ['device', ['vif']]]
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) parseConfig: result is {'shadow_memory': None, 'uuid': None, 'on_crash': None, 'on_reboot': None, 'localtime': None, 'image': ['linux', ['kernel', '/opt/kernel-current'], ['args', 'boot_verbose,boot_single,kern.hz=100,vfs.root.mountfrom=ufs:/dev/xbd769a']], 'on_poweroff': None, 'bootloader_args': None, 'cpus': None, 'name': 'freebsd', 'backend': [], 'vcpus': 1, 'cpu_weight': None, 'features': None, 'vcpu_avail': None, 'memory': 256, 'device': [('vbd', ['vbd', ['uname', 'file:/opt/mdroot-7.0'], ['dev', 'hda1'], ['mode', 'w']]), ('vif', ['vif'])], 'bootloader': None, 'cpu': None, 'maxmem': None}
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) XendDomainInfo.construct: None
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) XendDomainInfo.initDomain: 5 1.0
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) Balloon: 263020 KiB free; need 262144; done.
[2007-06-22 21:31:03 xend 2883] INFO (__init__:1072) buildDomain os=linux dom=5 vcpus=1
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) dom            = 5
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) image          = /opt/kernel-current
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) store_evtchn   = 1
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) console_evtchn = 2
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) cmdline        =  boot_verbose,boot_single,kern.hz=100,vfs.root.mountfrom=ufs:/dev/xbd769a
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) ramdisk        =
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) vcpus          = 1
[2007-06-22 21:31:03 xend 2883] DEBUG (__init__:1072) features       =
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] ERROR (__init__:1072) Domain construction failed
Traceback (most recent call last):
  File "/usr/lib/xen-3.0.3-1/lib/python/xen/xend/XendDomainInfo.py", line 195, in create
    vm.initDomain()
  File "/usr/lib/xen-3.0.3-1/lib/python/xen/xend/XendDomainInfo.py", line 1363, in initDomain
    raise VmError(str(exn))
VmError: (22, 'Invalid argument')
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) XendDomainInfo.destroy: domid=5
[2007-06-22 21:31:03 xend.XendDomainInfo 2883] DEBUG (__init__:1072) XendDomainInfo.destroyDomain(5)