Dear HDFS Issues, Hopefully this is the right place for my query. Today we migrated our Namenode to a new server as the old server was short on memory. We stopped the namenode service, copied its meta-data to the new server and started it on the new server. In between, we changed the hostname and IP address of the new server to be the same as the old server so that we wouldn't need to reconfigure all the cluster nodes to point to the new server.
Interestingly, when the new server booted the namenode service, it seems to have changed the ownership of a number of directories on the HDFS. We only noticed this when we came to run some jobs through Oozie and many of the jobs failed because the directories were now no longer owned by the Oozie user. We are now also seeing lots of warnings in the logs such as: > org.apache.hadoop.security.ShellBasedUnixGroupsMapping: got exception trying > to get groups for user webuser > org.apache.hadoop.util.Shell$ExitCodeException: id: webuser: No such user for this user and a few other users which were present on the old server and not on the new server. We can trivially re-create the users on the new server, but I'm not sure why that would cause some of the directories on HDFS to change ownership and not all of them. The only possible other explanation may be that when we booted the Namenode service for the first time, it started initially with the default blank configuration and not the configuration copied from the previous server. We stopped it before it got passed the merging of edits into the fsimage, so we're not entirely sure what the cause might be. Any further pointers as to what the cause might be would be gratefully received. We are using CDH3u3, however I don't think it's an issue specifically related to Cloudera's distribution. Thanks, Jamie
