This page describes most of the steps necessary to migrate an existing system into a Xen domainU. The process is still a bit rough around the edges. This example is based on a CentOS-3 system, but should be more-or-less applicable to others.
In this environment LVM is used for the virtual disks, and this fact determines the need to prepare the virtual disk prior to cloning. In a file-backed virtual disk environment, shortcuts could be made but at the cost of performance.
First create the storage (e.g. /dev/mapper/vg01/vol08 or /path/to/some/file) then run mkfs.ext3 on it and mount it as /mnt/disk
Prepwork (on srchost)
- Unmount any NFS or other network mounts e.g. smbfs
- package cleanup (optional)
- kernels - remove older unused kernels (e.g. rpm -qa | grep kernel ...)
- folder cleanup, look in /usr/src/, /usr/local/src/, /var/tmp/
- run yum clean or aptitude autoclean
- dry-run the rsync command below (-n) and redirect the output into /tmp/report
- review the report for any gotchas.
- look for any throw-away folders which can be added to the exclude file (to save disk space and time)
Create a file named XenCloneExlude containing these entries:
proc/* tmp/* lost+found/ etc/mtab
Now perform the rsync command as shown. This is just a test (dry) run.
rsync -av -e ssh -n \ #dry run -S \ # handle sparse files -H \ # Preserve hard links -W \ # copy files whole -D \ # also get device files --exclude-from="XenCloneExclude" \ root@srchost:/ /mnt/tmp
Or, more succintly...
rsync -av -e ssh -n -S -H -W -D --exclude-from="XenCloneExclude" root@srchost:/ /mnt/tmp
- fix up /etc/sysconfig/network-scripts/ifcfg-eth0 to use a different IP or to use PROTO=DHCP.
- Remake Devices? (oops - MAKEDEV is in /dev on redhat fix by scp'ing MAKEDEV over)
scp root@srchost:/dev/MAKEDEV /mnt/disk/dev/ cd /dev; ./MAKEDEV null random urandom console zero
- Fix /etc/fstab - because original is no longer valid!!!
First run as guest
Now you can exit the chroot and try to boot the vm.
This might be a good time to pull the plug on the old system 8)
Run this command to start the guest with a console attached
xm create newname -c
(Red Hat et al.) kudzu should run, remove all old devices
mv /lib/tls /lib/tls.disabled
Consider reviewing the network configuration.