Just wanted to share some success I had moving some Xen guests from one server to another.
Problem Recap We had Xen host on a single core 32-bit CentOS 5.4 installation on an AMD Athlon 2.1 GhZ system that was giving hard drive errors and needed to move the LVM-backed Xen images to another server. The replacement server was a quad-core AMD Phenom system running 64-bit CentOS 5.4.
Our original plan was to use LVM snapshots so that we wouldn't need a maintenance window. This worked fine in test, but we decided to bring down the Xen guests after all. After shutting down the systems we backed up the LVMs.
To show the backing LV: lvdisplay /dev/rootvg/xm_c32_001
From this, we grabbed the "Current LE" field and LV Size. We used LV
Size to create a temporary mount point. We used the "Current LE" parameter to create an identically sized LV on the replacement server .
On the failing server: dd if=/dev/rootvg/xm_c32_001 of=/mnt/backup/xm_c32_001.out
We gzip'ed the resulting .out file and saved it as a backup.
+++Footnote BTW, there are many recommendations to do the following on the virtual machine: dd if=/dev/zero bs=1024 count=xxxx of=/partition.out rm partition.out
By creating the large empty file on each partition *in the guest istance* (/var, /, /home, etc.), it will improve the image compression. Space was not much of a concern and we were worried about blowing out a production system, so we opted not to do this. +++Footnote
Once the backing LVM was created, we created the LV on the replacement server: lvcreate -l xxx -n xm_c32_001 rootvg
Then used dd to recreate the file: dd if=xm_c32_001.out of=/dev/rootvg/xm_c32_001
Next, we copied the /etc/xen/xm_c32_001 configuration file to the replacement server. We generated a new UUID using the "uuidgen" utility. We also created a new MAC address. Finally, we started the instance:
xm create xm_c32_001
Everything came up, but no network. From the root console we logged in then edited the /etc/sysconfig/network-scripts/ifcfg-eth0. Xen had apparently renamed the script and put in a DHCP configuration. We just renamed the backup file and commented out the MAC address line and restarted networking, *and* ifdown eth0 then ifup eth0.
It took a few seconds for the network to properly discover the new MAC address. Once that was done, everything worked beautifully.
Next, we copied the /etc/xen/xm_c32_001 configuration file to the replacement server. We generated a new UUID using the "uuidgen" utility. We also created a new MAC address. Finally, we started the instance:
Since you moved your virtual machine, you wouldn´t have to create a new UUID and no new MAC address. This is only required if you copy a virtual machine and if you want both up at the same time.
xm create xm_c32_001
Everything came up, but no network. From the root console we logged in then edited the /etc/sysconfig/network-scripts/ifcfg-eth0. Xen had apparently renamed the script and put in a DHCP configuration. We just renamed the backup file and commented out the MAC address line and restarted networking, *and* ifdown eth0 then ifup eth0.
This is because you changed the MAC address. If you would have left it at the original value, the network would have started right away with the old config.
Henry
Thanks Henry...
On Tue, Mar 2, 2010 at 2:10 AM, henry ritzlmayr centos@rc0.at wrote:
Next, we copied the /etc/xen/xm_c32_001 configuration file to the replacement server. We generated a new UUID using the "uuidgen" utility. We also created a new MAC address. Finally, we started the instance:
Since you moved your virtual machine, you wouldn´t have to create a new UUID and no new MAC address. This is only required if you copy a virtual machine and if you want both up at the same time.
Yes.. It's possible that we may have multiple copies of these systems.. Also, I un
xm create xm_c32_001
Everything came up, but no network. From the root console we logged in then edited the /etc/sysconfig/network-scripts/ifcfg-eth0. Xen had apparently renamed the script and put in a DHCP configuration. We just renamed the backup file and commented out the MAC address line and restarted networking, *and* ifdown eth0 then ifup eth0.
This is because you changed the MAC address. If you would have left it at the original value, the network would have started right away with the old config.
:D
Yes.. My error caused by re-using a script that autogenerated the config file. I had been playing with VMWare Lab Manager recently and was looking to emulate the template functionality in Xen.
On Mon, Mar 01, 2010 at 02:47:23PM -0500, Kwan Lowe wrote:
Just wanted to share some success I had moving some Xen guests from one server to another.
Problem Recap We had Xen host on a single core 32-bit CentOS 5.4 installation on an AMD Athlon 2.1 GhZ system that was giving hard drive errors and needed to move the LVM-backed Xen images to another server. The replacement server was a quad-core AMD Phenom system running 64-bit CentOS 5.4.
Our original plan was to use LVM snapshots so that we wouldn't need a maintenance window. This worked fine in test, but we decided to bring down the Xen guests after all. After shutting down the systems we backed up the LVMs.
To show the backing LV: lvdisplay /dev/rootvg/xm_c32_001
From this, we grabbed the "Current LE" field and LV Size. We used LV
Size to create a temporary mount point. We used the "Current LE" parameter to create an identically sized LV on the replacement server .
On the failing server: dd if=/dev/rootvg/xm_c32_001 of=/mnt/backup/xm_c32_001.out
We gzip'ed the resulting .out file and saved it as a backup.
+++Footnote BTW, there are many recommendations to do the following on the virtual machine: dd if=/dev/zero bs=1024 count=xxxx of=/partition.out rm partition.out
By creating the large empty file on each partition *in the guest istance* (/var, /, /home, etc.), it will improve the image compression. Space was not much of a concern and we were worried about blowing out a production system, so we opted not to do this. +++Footnote
Once the backing LVM was created, we created the LV on the replacement server: lvcreate -l xxx -n xm_c32_001 rootvg
Then used dd to recreate the file: dd if=xm_c32_001.out of=/dev/rootvg/xm_c32_001
Next, we copied the /etc/xen/xm_c32_001 configuration file to the replacement server. We generated a new UUID using the "uuidgen" utility. We also created a new MAC address.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Finally, we started the instance:
xm create xm_c32_001
Everything came up, but no network. From the root console we logged in then edited the /etc/sysconfig/network-scripts/ifcfg-eth0. Xen had apparently renamed the script and put in a DHCP configuration.
It's not Xen renaming the script :) You changed the MAC address, so the centos network init scripts will rename the ifcfg file, and generate new default one (with dhcp).
rhel/centos ifcfg-eth* are based on MAC addresses.
-- Pasi
We just renamed the backup file and commented out the MAC address line and restarted networking, *and* ifdown eth0 then ifup eth0.
It took a few seconds for the network to properly discover the new MAC address. Once that was done, everything worked beautifully. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On Tue, Mar 2, 2010 at 4:14 AM, Pasi Kärkkäinen pasik@iki.fi wrote:
It's not Xen renaming the script :) You changed the MAC address, so the centos network init scripts will rename the ifcfg file, and generate new default one (with dhcp).
rhel/centos ifcfg-eth* are based on MAC addresses.
Thanks Pasi... Pretty cool feature... I was overly enthusiastic in trying to figure out why I couldn't see the vm after I booted it. If I'd waited or re-arp'ed it would have worked without my meddling. Chalk a point up for CentOS :P
The network should not have been an issue, are you sure you used the same vm config on both hosts? That means the mac address would stay the same, and their should not be any L2 related issues, that are related to vm anyway.
Ted
On Mar 1, 2010, at 2:47 PM, Kwan Lowe wrote:
Just wanted to share some success I had moving some Xen guests from one server to another.
Problem Recap We had Xen host on a single core 32-bit CentOS 5.4 installation on an AMD Athlon 2.1 GhZ system that was giving hard drive errors and needed to move the LVM-backed Xen images to another server. The replacement server was a quad-core AMD Phenom system running 64-bit CentOS 5.4.
Our original plan was to use LVM snapshots so that we wouldn't need a maintenance window. This worked fine in test, but we decided to bring down the Xen guests after all. After shutting down the systems we backed up the LVMs.
To show the backing LV: lvdisplay /dev/rootvg/xm_c32_001
From this, we grabbed the "Current LE" field and LV Size. We used LV
Size to create a temporary mount point. We used the "Current LE" parameter to create an identically sized LV on the replacement server .
On the failing server: dd if=/dev/rootvg/xm_c32_001 of=/mnt/backup/xm_c32_001.out
We gzip'ed the resulting .out file and saved it as a backup.
+++Footnote BTW, there are many recommendations to do the following on the virtual machine: dd if=/dev/zero bs=1024 count=xxxx of=/partition.out rm partition.out
By creating the large empty file on each partition *in the guest istance* (/var, /, /home, etc.), it will improve the image compression. Space was not much of a concern and we were worried about blowing out a production system, so we opted not to do this. +++Footnote
Once the backing LVM was created, we created the LV on the replacement server: lvcreate -l xxx -n xm_c32_001 rootvg
Then used dd to recreate the file: dd if=xm_c32_001.out of=/dev/rootvg/xm_c32_001
Next, we copied the /etc/xen/xm_c32_001 configuration file to the replacement server. We generated a new UUID using the "uuidgen" utility. We also created a new MAC address. Finally, we started the instance:
xm create xm_c32_001
Everything came up, but no network. From the root console we logged in then edited the /etc/sysconfig/network-scripts/ifcfg-eth0. Xen had apparently renamed the script and put in a DHCP configuration. We just renamed the backup file and commented out the MAC address line and restarted networking, *and* ifdown eth0 then ifup eth0.
It took a few seconds for the network to properly discover the new MAC address. Once that was done, everything worked beautifully. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On Tue, Mar 2, 2010 at 11:07 PM, Ted Kaczmarek tedkaz@gmail.com wrote:
The network should not have been an issue, are you sure you used the same vm config on both hosts? That means the mac address would stay the same, and their should not be any L2 related issues, that are related to vm anyway.
It appears to have been my error and the vmware config didn't need to be changed. I'd originally copied the file unchanged, but on the new host the network did not seem to be working. If I'd have waited a few more minutes the switches probably would have caught up.
-
henry ritzlmayr -
Kwan Lowe -
Pasi Kärkkäinen -
Ted Kaczmarek