How to check if Hadoop daemons are running?

Question

What are simple commands to check if Hadoop daemons are running?

For example if I\'m trying to figure out why HDFS is not setup correctly I\'ll want to know a way to ch

Answer 1

If you see hadoop process is not running on ps -ef|grep hadoop, run sbin/start-dfs.sh. Monitor with hdfs dfsadmin -report:

[mapr@node1 bin]$ hadoop dfsadmin -report
Configured Capacity: 105689374720 (98.43 GB)
Present Capacity: 96537456640 (89.91 GB)
DFS Remaining: 96448180224 (89.82 GB)
DFS Used: 89276416 (85.14 MB)
DFS Used%: 0.09%
Under replicated blocks: 0
Blocks with corrupt replicas: 0
Missing blocks: 0

-------------------------------------------------
Datanodes available: 2 (2 total, 0 dead)

Name: 192.168.1.16:50010
Decommission Status : Normal
Configured Capacity: 52844687360 (49.22 GB)
DFS Used: 44638208 (42.57 MB)
Non DFS Used: 4986138624 (4.64 GB)
DFS Remaining: 47813910528(44.53 GB)
DFS Used%: 0.08%
DFS Remaining%: 90.48%
Last contact: Tue Aug 20 13:23:32 EDT 2013


Name: 192.168.1.17:50010
Decommission Status : Normal
Configured Capacity: 52844687360 (49.22 GB)
DFS Used: 44638208 (42.57 MB)
Non DFS Used: 4165779456 (3.88 GB)
DFS Remaining: 48634269696(45.29 GB)
DFS Used%: 0.08%
DFS Remaining%: 92.03%
Last contact: Tue Aug 20 13:23:34 EDT 2013

Answer 2

I did not find great solution to it, so I used

ps -ef | grep hadoop | grep -P  'namenode|datanode|tasktracker|jobtracker'

just to see if stuff is running

and

./hadoop dfsadmin -report

but last was not helpful until server was running.

Answer 3

In the shell type 'jps' (you might need a jdk to run jps). It lists all the running java processes and will list out the hadoop daemons that are running.