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Last active Aug 29, 2015
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XenServer Notes

Citrix Xenserver

Citrix Xenserver is a beautiful open source (from 6.2 edition and later) hypervisor that tries to grab as much as possible market share on virtualization/cloud world. It carries many years of development efforts by Citrix, many well established implementations and a broad support community. XenMotion, High Availability and all the great features of Xenserver are available on the licensed and unlicensed versions of the hypervisor.

Applying Hotfixes

The licensed version includes automated patches and updates through XenCenter console and 24×7 Citrix Technical Support. On the unlicensed version, the administrator should apply the xenserver patches by himself through an ssh console. XenCenter still notifies the availability of new patches.

So, on XenCenter when you goto Tools – Install Updates, you get grayed out options. To manually apply the updates, first of all we should download the new patches from Citrix webserver, XenCenter will help you to do so. Then unzip the contents of the downloaded files and secure ftp them on XenServer.

I use filezilla to sftp the updates to XenServer in binary transfer mode and upload them to /var/tmp directory. Then ssh to XenServer (I use putty utility to do so but you can use anything you are comfortable with). Login as root and run the following command

xe patch-upload file-name=/var/tmp/<update file>

this command produces a uuid alphanumeric string. Copy it to the clipboard and on XenCenter notice the yellow down icons that appear, indicating that a hotfix or update exists but has not been applied. XenCenter warning icon

xe patch-pool-apply uuid=<uuid>

pasting the uuid string. You may verify the applied patches by running

xe patch-list

If the update has been successful, the hosts field should contain the uuids of all the hosts in the pool. Finally, run

xe-toolstack-restart

to reload the toolstack on all hosts, you may loose the connection if you run it on Pool Master. Applying Patches

Now, your XenServer is patched!

Ubuntu / Debian Linux Regenerate OpenSSH Host Keys

To regenerate keys you need to delete old files and reconfigure openssh-server. It is also safe to run following commands over remote ssh session. Your existing session shouldn't be interrupted.

  1. Delete old ssh host keys

Login as the root and type the following command:

# rm /etc/ssh/ssh_host_*
  1. Reconfigure OpenSSH Server

Now create a new set of keys, enter:

# dpkg-reconfigure openssh-server
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