[Xen-bugs] [Bug 1001] New: Xen auto feature does not save and restore correctly.

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http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1001

           Summary: Xen auto feature does not save and restore correctly.
           Product: Xen
           Version: 3.0.3
          Platform: x86-64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Guest-OS
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: JohnWmAustin@xxxxxxxxx


I have two guest systems that I have been using for about a week with no
problems.

When I created links to them in /etc/xen/auto, they started up correctly the
first time I restarted the system. 

On subsequent system restarts, these DomU guests were not restarted. On
examination of the logs it appears that the system is failing to save the
images.

I note that the XendCheckpoint.py module reports this error as:

[2007-06-19 23:32:47 xend 3129] ERROR (XendCheckpoint:106) Save failed on
domain CC_test (4).
Traceback (most recent call last):
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendCheckpoint.py", line
100, in save
    forkHelper(cmd, fd, saveInputHandler, False)
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendCheckpoint.py", line
227, in forkHelper
    raise XendError("%s failed" % string.join(cmd))
XendError: /usr/lib64/xen/bin/xc_save 21 4 0 0 0 failed

If you take the time to examine the Python code, you may notice that the error
code is not reported. There is one message for a specific error condition and a
generic message that omits the cause for any other conditions. This is a minor
error that probably contributes to the couple of dozen similar reports you have
about this problem.

    status = child.wait()
    if status >> 8 == 127:
        raise XendError("%s failed: popen failed" % string.join(cmd))
    elif status != 0:
        raise XendError("%s failed" % string.join(cmd))

I have been able to circumvent the problem by deleting the save files after a
successful system restart. This allows Xen to save the guests to new image
files that it can use to restore them after the reboot. If these files are not
deleted, subsequent save operations (initiated by a normal shutdown) will fail.

Two things need to be done:

1) delete the save files after they have been used to restart the associated
DomUs (or delete before saving).

2) think about writing better error messages in the Python code.

Thank you.


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