I updated a server running SLES11 from SP2 to SP3, and in the 24 hours since I did this the server has rebooted twice for no apparent reason. Running SP2, the uptime was at least one year. Does anyone have any suggestions as to how to find out the reason for this instability? I have of course looked in the logs but I cannot find anything that explains this behaviour. In both cases, /var/log/messages contained nothing for at least 5 minutes before times of the reboots.
The update procedure was routine: I applied all pending patches for SP2, and then used wagon to apply SP3. No errors or difficulties were encountered during this process.
The server is hosting several virtual machines (qemu-kvm), and the behaviour of libvirtd is the only other odd thing that I have noticed. After starting or restarting the libvirtd service, "virsh list" appears to hang, although after several minutes it does start responding as normal. Also virt-manager now takes several minutes after opening a connection before the guests are displayed. I do not know if this is connected with the server reboots.
The other thing that I can think of that may be relevant is that for historical reasons we have disabled IPv6 on this system, although if this is likely to be a source of problems we could reconsider this.
I would be very grateful for any hints or suggestions.