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Bug 795127

Summary: pre-migration hook needed at destination
Product: Red Hat Enterprise Linux 6 Reporter: Dan Kenigsberg <danken>
Component: libvirtAssignee: Jiri Denemark <jdenemar>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.2CC: abaron, acathrow, dallan, dyuan, fsimonce, mshao, mzhan, rwu, weizhan, whuang, zhpeng
Target Milestone: rcKeywords: FutureFeature
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: libvirt-0.9.10-4.el6 Doc Type: Enhancement
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2012-06-20 06:48:39 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Dan Kenigsberg 2012-02-19 14:27:40 UTC 
Description of problem:
virDomainMigrateURI2() lets the client play with the domxml at the destination host. However, more common than not, the client does not (or should not) know about specifics of the destination host (where storage is mounted there, name of network interface, ...).

I would like to be able to tweak incoming domxml at the destination host before `qemu -incoming` is started. This would let a complex client application mount storage, activate LVs, create local cdrom image for vm-specific data (and much more) before the VM starts.
Comment 1 Jiri Denemark 2012-02-28 21:52:17 UTC 
Initial patches sent upstream for review: https://www.redhat.com/archives/libvir-list/2012-February/msg01146.html
Comment 2 Jiri Denemark 2012-02-29 13:14:05 UTC 
In POST: http://post-office.corp.redhat.com/archives/rhvirt-patches/2012-February/msg01599.html
Comment 4 weizhang 2012-03-06 12:23:45 UTC 
Hi Jiri,

What should I write on qemu hooks on source and target host?
Comment 5 Jiri Denemark 2012-03-06 13:35:27 UTC 
The hook will only be called on target host as

    /etc/libvirt/hooks/qemu DOMAIN migrate begin -

with the DOMAIN's XML sent to stdin of the script. So you need to do something in the script when $2 is equal to "migrate". You can either do nothing (i.e, exit 0) or copy stdin to stdout (e.g., cat) to use the domain XML without any changes. Or you can try to change something in the input XML (using sed, for example).
Comment 8 xhu 2012-03-08 07:22:01 UTC 
Verify it with libvirt-0.9.10-4.el6.x86_64 and it passed:
1 setup migration env on both source and target machine
2 prepare /etc/libvirt/hooks/qemu script file on target machine:
# cat /etc/libvirt/hooks/qemu 
#! /bin/bash
echo "$0" "$@" >> /tmp/qemu.log
exit 0

# chmod +x /etc/libvirt/hooks/qemu
3 start migration
# virsh migrate ${guestname} qemu+ssh://${target_ip}/system --unsafe
4 check /tmp/qemu.log on target machine:
# cat /tmp/qemu.log 
/etc/libvirt/hooks/qemu kvm-rhel6-i386 migrate begin -
/etc/libvirt/hooks/qemu kvm-rhel6-i386 prepare begin -
/etc/libvirt/hooks/qemu kvm-rhel6-i386 start begin -
Comment 10 errata-xmlrpc 2012-06-20 06:48:39 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0748.html