Failure to start Hadoop after having stopped a running (and working) instance before, because Datanode says that the directory is locked - hadoop

Question

I have a cluster running Hadoop 1.2.1 with Giraph on top. The server runs ok, but when I stop it, I am unable to make it run again. In the datanode log I get the following error: ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Cannot lock storage /pathToFolder/data/datanode. The directory is already locked.
I have tried many solutions that I found online:
Checking permissions of folders.
Checking equal versions of VERSION file for namenode and datanode.
Checking configuration files (core-site, hdfs-site, mapred-site, master, slaves, ...)
Deleting / Changing the namenode and datanode data folders
Removing hadoop temporary files
Bottomline is, everything seems fine, but it is still failing to start the datanode. A complete log file for the datanode is the following:
2020-06-24 11:23:46,624 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: STARTUP_MSG:
/********************
STARTUP_MSG: Starting DataNode
STARTUP_MSG: host = XXXX
STARTUP_MSG: args = []
STARTUP_MSG: version = 1.2.1
STARTUP_MSG: build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2 -r 1503152; compiled by 'mattf' on Mon Jul 22 15:23:09 PDT 2013
STARTUP_MSG: java = 1.8.0_212
********************/
2020-06-24 11:23:46,719 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties
2020-06-24 11:23:46,725 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source MetricsSystem,sub=Stats registered.
2020-06-24 11:23:46,726 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 second(s).
2020-06-24 11:23:46,726 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: DataNode metrics system started
2020-06-24 11:23:46,791 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source ugi registered.
2020-06-24 11:23:46,794 WARN org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Source name ugi already exists!
2020-06-24 11:23:46,903 INFO org.apache.hadoop.hdfs.server.common.Storage: Cannot lock storage /users/lahdak/rojas/AppHadoop/data/datanode. The directory is already locked.
2020-06-24 11:23:47,004 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Cannot lock storage /users/lahdak/rojas/AppHadoop/data/datanode. The directory is already locked.
at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.lock(Storage.java:599)
at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.analyzeStorage(Storage.java:452)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:111)
at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:414)
at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:321)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1712)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1651)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1669)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1795)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1812)
2020-06-24 11:23:47,004 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: SHUTDOWN_MSG:
/********************
SHUTDOWN_MSG: Shutting down DataNode at XXXX
********************/

Answer 1

Still haven't managed to get rid of the problem (Datanode not shutting down correctly), but I found a workaround to the situation. I used lsof +D /pathto detect active processes and killed them. The weird part is that this process was invisible to top and jps commands.