On Fri, Nov 11, 2011 at 10:28 AM, Benjamin Weaver
<
benjamin.weaver@xxxxxxxxxxxxx<mailto:
benjamin.weaver@xxxxxxxxxxxxx>>
wrote:
I am running xen 4.0.1 with debian squeeze (kernel:
Linux version 2.6.32-5-xen-amd64 (Debian 2.6.32-38).
Below is output indicating the problem.
My vms are Ubuntu (lucid). I cannot save and restore my
vms properly. A lucid vm works fine when first created
by xm create. But then, when I save (xm save hostname
filename), and restore from that file (xm restore
filename). I get a vm that lets me login, but then
freezes its prompt.
This problem with lucid vms surfaced only a few weeks
ago, before which I was running linux-base 2.6.32-35.
The problem is related to Bug #644604 (
http://lists.debian.org/debian-kernel/2011/10/msg00183.html).
I had gotten some good suggestions on how and whether to
compile a kernel version later than Squeeze, but had
some difficulties compiling and in any event would like
to get a stable release to run my vms.
MY GUESS AT THE PROBLEM: I have since come to suspect a
problem of communication between Xen Virtual Block
Devices, Xen drivers (frontend and backend) and dom0
drivers that I thought be fixable.
Please confirm if so; any suggestions as to how to fix
this problem would be greatly appreciated!
Output (see below)
I notice a couple of things:
1. a.when the lucid vm is created a df command shows
only xvda2 showing up as a filesystem; b. an lsmod shows
only xen_blkfront and xen_netfront. This is all in
contrast to output from the same commands regarding a
hardy or lenny vm. In these cases, df shows several
active file systems, and lsmod shows several modules,
ipv6, jbd, etc., in fact several things except
xen_blkfront and xen_netfront.
2. after the lucid vm is saved no reads or writes are
being done to its VBDs.
# df command on lenny
Filesystem 1K-blocks Used Available Use%
Mounted on
/dev/xvda2 2064208 392684 1566668 21%
/
varrun 262252 28 262224 1%
/var/run
varlock 262252 0 262252 0%
/var/lock
udev 262252 12 262240 1%
/dev
devshm 262252 0 262252 0%
/dev/shm
root@lucidxentest3:~#
# df command on lucid
Filesystem 1K-blocks Used Available Use%
Mounted on
/dev/xvda2 2064208 545596 1413756 28%
/
none 240380 120 240260 1%
/dev
none 252152 0 252152 0%
/dev/shm
none 252152 28 252124 1%
/var/run
none 252152 0 252152 0%
/var/lock
none 252152 0 252152 0%
/lib/init/rw
root@lucidxentest:~#
# lsmod on lucid vm
Module Size Used by
xen_netfront 17890 0
xen_blkfront 10665 2
root@lucidxentest:~#
# lsmod on hardy vm
Module Size Used by
ipv6 313960 10
evdev 15360 0
ext3 149520 1
jbd 57256 1 ext3
mbcache 11392 1 ext3
root@lucidxentest3:~#
Before xm save, VBDs on lucid vm show read/write
activity with non-zero values.
After save, xm top shows lucid vm VBDs with zeroed-out
values for read/write. That is, values of 0 under the
following columns of xm top output:
VBD_OO VBD_RD VBD_WR VBD_RSECT VBD_WSECT.
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