Eucalyptus Versions: 3.0 and above.
This article describes the scenario in which you might see the following (example) errors in nc.log on a Node Controller:
2014-02-20 16:00:34 ERROR | [i-347441BC] failed to remove some artifacts in /var/lib/eucalyptus/instances/work/AIDHTYISEIUBZHQTKQ7SA/i-347441BC 2014-02-20 16:00:34 WARN | [i-347441BC] failed to remove backing directory /var/lib/eucalyptus/instances/work/AIDHTYISEIUBZHQTKQ7SA/i-347441BC
These error messages indicate that upon termination of an instance the Node Controller was unable to remove some storage links and the directory used to store the instance artifacts (such a storage links, libvirt xml and console log).
This is mostly harmless but does leave behind a directory with some redundant files. If this error messages is seen you should perform the following steps:
1) Check the instance has indeed been terminated by running "virsh list" on the hypervisor (Node Controller)
2) Remove the backing directory mentioned in the log message together with the files inside.
This is a known issue and is being tracked in this bug ticket: https://eucalyptus.atlassian.net/browse/EUCA-9069