start xen error

#xm list

Error: Unable to connect to xend: No such file or directory. Is xend running?

log:

[2012-12-20 10:48:29 5573] INFO (SrvDaemon:332) Xend Daemon started
[2012-12-20 10:48:29 5573] INFO (SrvDaemon:336) Xend changeset: unavailable.
[2012-12-20 10:48:31 5573] DEBUG (XendNode:332) pscsi record count: 1
[2012-12-20 10:48:31 5573] DEBUG (XendCPUPool:747) recreate_active_pools
[2012-12-20 10:48:31 5573] ERROR (SrvDaemon:349) Exception starting xend ((19, 'No such device'))
Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/xen/xend/server/SrvDaemon.py", line 341, in run
    servers = SrvServer.create()
  File "/usr/lib/python2.6/dist-packages/xen/xend/server/SrvServer.py", line 258, in create
    root.putChild('xend', SrvRoot())
  File "/usr/lib/python2.6/dist-packages/xen/xend/server/SrvRoot.py", line 40, in __init__
    self.get(name)
  File "/usr/lib/python2.6/dist-packages/xen/web/SrvDir.py", line 84, in get
    val = val.getobj()
  File "/usr/lib/python2.6/dist-packages/xen/web/SrvDir.py", line 52, in getobj
    self.obj = klassobj()
  File "/usr/lib/python2.6/dist-packages/xen/xend/server/SrvNode.py", line 30, in __init__
    self.xn = XendNode.instance()
  File "/usr/lib/python2.6/dist-packages/xen/xend/XendNode.py", line 1181, in instance
    inst = XendNode()
  File "/usr/lib/python2.6/dist-packages/xen/xend/XendNode.py", line 163, in __init__
    self._init_cpu_pools()
  File "/usr/lib/python2.6/dist-packages/xen/xend/XendNode.py", line 382, in _init_cpu_pools
    XendCPUPool.recreate_active_pools()
  File "/usr/lib/python2.6/dist-packages/xen/xend/XendCPUPool.py", line 754, in recreate_active_pools
    uuid = xstransact.Read(path, 'uuid')
  File "/usr/lib/python2.6/dist-packages/xen/xend/xenstore/xstransact.py", line 307, in Read
    return complete(path, lambda t: t.read(*args))
  File "/usr/lib/python2.6/dist-packages/xen/xend/xenstore/xstransact.py", line 361, in complete
    t = xstransact(path)
  File "/usr/lib/python2.6/dist-packages/xen/xend/xenstore/xstransact.py", line 29, in __init__
    self.transaction = xshandle().transaction_start()
Error: (19, 'No such device')
[2012-12-20 10:48:31 5572] INFO (SrvDaemon:220) Xend exited with status 1.

resulovtion : Start /etc/init.d/xencommons before starting xend.