Can't open /tmp/mapr-hadoop/mapred/local/taskTracker/root/jobcache//jobToken for output - File exists

If you hit this error on any task attempt :

Can't open /tmp/mapr-hadoop/mapred/local/taskTracker/root/jobcache/job_201402140511_0001/jobToken for output - File exists

Eg.

14/02/14 06:07:09 INFO mapred.JobClient: Task Id : attempt_201402140511_0001_r_000001_0, Status : FAILED on node nmk-centos-60-3
Error initializing attempt_201402140511_0001_r_000001_0 java.io.IOException: Job initialization failed (255). with output: Reading task controller config from /opt/mapr/hadoop/hadoop-0.20.2/conf/taskcontroller.cfg
number of groups = 8
main : command provided 0
main : user is root
number of groups = 7
Can't open /tmp/mapr-hadoop/mapred/local/taskTracker/root/jobcache/job_201402140511_0001/jobToken for output - File exists
failed to copy credential file

at org.apache.hadoop.mapred.LinuxTaskController.initializeJob(LinuxTaskController.java:195)
at org.apache.hadoop.mapred.TaskTracker$4.run(TaskTracker.java:1564)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)
at org.apache.hadoop.mapred.TaskTracker.initializeJob(TaskTracker.java:1540)
at org.apache.hadoop.mapred.TaskTracker.localizeJob(TaskTracker.java:1425)
at org.apache.hadoop.mapred.TaskTracker$6.run(TaskTracker.java:3802)
Caused by: org.apache.hadoop.util.Shell$ExitCodeException:
at org.apache.hadoop.util.Shell.runCommand(Shell.java:322)
at org.apache.hadoop.util.Shell.run(Shell.java:249)
at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:442)
at org.apache.hadoop.mapred.LinuxTaskController.initializeJob(LinuxTaskController.java:188)

Chances are that you have either of the two issues :

1) Different UID GID mapping for the same user on the nodes in the cluster 

2) Incorrect credentials for /tmp/mapr-hadoop folder on the tasktracker where the job failed.

The simple fix for that is :

Stop tasktracker
Remove /tmp/mapr-hadoop/
Start TT again
Run job