Hudson wasn't generating the backup file. The permissions on /var/hudson/ didn't allow writes. Hudson/Backup Plugin didn't provide any notice of this, nor did it cancel the operation. Before I noticed the permissions were wrong I tried to add a comment to http://issues.jenkins-ci.org/browse/JENKINS-5669, and cloned the bug expecting an option to append text. I Fail'd it. http://issues.jenkins-ci.org/browse/JENKINS-6320 can be closed.

The next problem:

[ INFO] Backup started at [04/20/10 22:40:06] [ INFO] Setting hudson in shutdown mode to avoid files corruptions. [ INFO] Waiting all jobs end... [ INFO] Number of running jobs detected : 0
[ INFO] All jobs finished. [ INFO] Full backup file name : /var/hudson/backup_20100420_2240.tar.bz2
[ERROR] org.codehaus.plexus.archiver.ArchiverException: Failed to read filesystem attributes for: /home/fldbuild/.hudson/war/images/16x16/red_anime.gif org.jvnet.hudson.plugins.backup.BackupException: java.io.IOException: Unable to add war/images/16x16/red_anime.gif at org.jvnet.hudson.plugins.backup.utils.BackupEngine.doBackup(BackupEngine.java:115) at org.jvnet.hudson.plugins.backup.utils.BackupTask.run(BackupTask.java:125) at java.lang.Thread.run(Thread.java:619) Caused by: java.io.IOException: Unable to add war/images/16x16/red_anime.gif at org.jvnet.hudson.plugins.backup.utils.BackupEngine.handleFile(BackupEngine.java:90) at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:367) at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364) at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364) at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364) at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:335) at org.jvnet.hudson.plugins.backup.utils.BackupEngine.doBackup(BackupEngine.java:113) ... 2 more [ INFO] Cancel hudson shutdown mode [ INFO] Backup end at [04/20/10 22:40:56] [ INFO] [49.631s]