hadoop cluster boot sequenceZookeepeer->hadoop->hbase
Hadoop cluster shutdown sequenceHbase->hadoop->zookeepeer
Hadoop Primary and Standby node Status View and manual switchover$HADOOP _home/bin/hdfs haadmin-getservicestate nn1
Note: The nn1 here is the name of the Namenode service configured in Hdfs-site.xml.
$HADOOP _home/bin/hdfs haadmin-failover--forcefence--forceactive nn2 nn1
Note: The order of "Nn2 nn1" here indicates that the active state is converted from NN2 to NN1 (although NN2 can also be standby before conversion).
Safe ModeDfsadmin-safemode value to operate the Safe mode, the parameter value is described as follows:
Enter-Enter Safe mode
Leave-Force Namenode to leave Safe mode
Get-Returns information about whether Safe mode is turned on
Wait-waits until the end of safe mode.
Block Loss RepairFiles damaged by using Hadoop fsck/list corrupted files cannot be recovered, only corrupted files can be deleted Hadoop fsck-delete
Slow when Namenode file information is large and affects Hadoop performance usage:hadoop fsck <path> [-list-corruptfileblocks | [-move |-delete |-openforwrite] [-files [-blocks [-locations |-racks]]
<path> Check the starting directory
-move to move corrupted files to/lost+found
-delete Deleting corrupted files
-files Print out all the checked files
-openforwrite print out files that are being written
-list-corruptfileblocks print out list of missing blocks and files they belong to
-blocks Print out the Block report
-locations print out the location of each block
-racks Print out the Data-node network topology
By default, fsck ignores files that are being written, and uses-openforwrite to report such files
