One node is Black listed in CDH 5.4.2 12 node Cloudera Hadoop cluster .
Reason for Black list : 27 failures on the tracker
Please help to find out the resolution.
This article from Stack Overflow may be helpful.
In general a blacklisted node can be brought back online by cleaning up the errors. You will need to look at the task tracker logs to see what was causing the failures. Let me know what happens.