I had a XenServer that wouldn’t list the NICs in the XenServer configuration at all. Linux saw the NICs just fine but you couldn’t ifup the NICs itself.

There are articles out there telling you to change your network-scripts directories. Never do this according to a Citrix rep.

Run xe host-is-in-emergency-mode to check if it is in emergency mode… If it is then runxe pool-emergency-reset-master if you are on the master. If you are on a host then run xe pool-emergency-reset-master master address=address-of-the-pool-master. If you master is dead and you want to promote a host then run xe pool-emergency-transition-to-master to recover the machine.

The command sounds dangerous but if you are only recovering a non-master host, then it really just resets the emergency mode and re syncs with the master. I’ve had to do it a couple of times now.

Read the snippet below.

2.6.2. Master failures

Every member of a Resource Pool contains all the information necessary to take over the role of master if required. When a master node fails, the following sequence of events occurs:

  1. The slaves realize that communication has been lost and each retry for sixty seconds
  2. Each slave then puts itself into emergency mode, whereby the slave XenServer Hosts will now accept only the pool-emergency commands (xe pool-emergency-reset-masterand xe pool-emergency-transition-to-master).

If the master comes back up at this point, it will reestablish communication with its slaves, they will leave emergency mode, and operation will return to normal.

If the master is really dead, though, you should choose one of the slaves and issue to it the command xe pool-emergency-transition-to-master. Once it has become the master, issue the command xe pool-recover-slaves and the slaves will now point to the new master.

If you repair or replace the server that was the original master, you can simply bring it up, install the XenServer Host software, and add it to the pool. Since the XenServer Hosts in the pool are enforced to be homogeneous, there is no real need to make the replaced server the master.

When a slave host is transitioned to being a master, you should also check that the default pool storage repository is set to an appropriate value. This can be done using the xe pool-param-list command and verifying that the default-SR is pointing to a valid storage repository.