When running OpenStack compute, using a shared filesystem or an automated configuration tool, you could encounter a situation where some files on your compute node are using the wrong UID or GID. This causes a raft of errors, such as being unable to live migrate, or start virtual machines.
The following is a basic procedure run on nova-compute hosts, based on the KVM hypervisor, that could help to restore the situation:
First,make sure you don't use numbers that are already used for some other user/group.
Set the nova uid in /etc/passwd to the same number in all hosts (e.g. 112)
Set the libvirt-qemu uid in /etc/passwd to the same number in all hosts (e.g. 119)
Set the nova group in /etc/group file to the same number in all hosts (e.g. 120)
Set the libvirtd group in /etc/group file to the same number in all hosts (e.g. 119)
Stop the services on the compute node
Change all the files owned by nova or group by nova, e.g.
find / -uid 108 -exec chown nova {} \; # note the 108 here is the old nova uid before the change find / -gid 120 -exec chgrp nova {} \;Repeat the steps for the libvirt-qemu owned files if those were needed to change
Restart the services
Following this, you can run the find command to verify that all files using the correct identifiers.
