After upgrading from 1.415 to 1.421 the symlinks for builds/$(buildNumber}, lastSuccessful and lastStable are not created. The relevant lines from the build output are

ln -s 2011-07-20_18-21-48 /var/lib/jenkins/jobs/ps-indexer/builds/877 failed: -1

at the beginning of the build and

ln -s builds/2011-07-20_18-21-48 /var/lib/jenkins/jobs/ps-indexer/builds/../lastSuccessful failed: -1
ln -s builds/2011-07-20_18-21-48 /var/lib/jenkins/jobs/ps-indexer/builds/../lastStable failed: -1

at the end.

This used to work before the update and no other changes were made in the system.

We worked around this issue by adding

-Dhudson.Util.symlinkEscapeHatch=true

to JAVA_ARGS in /etc/default/jenkins.

BTW: Util.createSymlink produces ambiguous logging output for failures. It logs "ln -s ..." even though JNA or PosixAPI may have been used. Furthermore, the PosixAPI fall-back branch does not clear the errmsg variable such the strerror value from JNA gets mixed up with the result code from PosixAPI. Last but not least, it mixes string paths with file objects. It would make sense to move the logging code into the branch for each method (JNA, PosixAPI and LocalProc) and log the actual parameters passed.