Citrix XenServer XAPI Not running

Issue

A XenServer node is not available in the pool - all VM's running on the server have stopped/migrated to other nodes.

When logging into the server via the DRAC card the following message is displayed:

"The XenA API xapi is not running. This console will have reduced functionality."

Resolution - lifted from http://support.citrix.com/article/CTX128316

•  The most common cause is that the XenServer disk has ran out of space.  Usually because a log file has grown especially large.
• Open the console via Putty/any SSH terminal (The server will not be available in XenCenter)
• Typr df in the console - this will show you the current disk use - you will see a "Use%" listed as the 5th column, if this shows at or very near 100% then disk space is probably the issue

My usage is at 54%

• The most common cause of disk space being used is the logs in /var/log so do the following:
• cd /var/log
• Run the following command to see the size of all the files in the current directory; narrow down your search by specifying one file, if needed:
• du –ksh *.*
• If you see an excessively large file, run the following command to delete the file:
• rm <filename>.log.
• Restart the XenServer to recreate the log file and it restarts XAPI automatically.