From any node in a Hadoop cluster, what is the command to
identify the running namenode?
identify all running datanodes?
I have looked through the commands manual and have not found this.
Use the dfsadmin command:
bin/hadoop dfsadmin -report
Update (2015):
bin/hdfs dfsadmin -report
Try this:
hdfs getconf -namenodes
hdfs getconf -secondaryNamenodes
Try This. For dfsadmin not every user has permission.
hdfs getconf -confKey fs.defaultFS
hdfs://XYZ
2016 update, following Tejas answer:
hadoopuser#gsamaras:~/hadoop/bin$ ./hdfs dfsadmin -report
Related
I upgrade to the latest version of cloudera.Now I am trying to create directory in HDFS
hadoop fs -mkdir data
Am getting the following error
Cannot Create /user/cloudera/data Name Node is in SafeMode.
How can I do this?
When you start hadoop, for some time limit hadoop stays in safemode. You can either wait (you can see the time limit being decreased on Namenode web UI) until the time limit or You can turn it off with
hadoop dfsadmin -safemode leave
The above command turns off the safemode of hadoop
In addition to Ramesh Maharjan answer, By default, cloudera machine(Cloudera Quick Start#5.12) doesn't allow to SET OFF safe mode, it's required to specify the -u options as shown below:
sudo -u hdfs hdfs dfsadmin -safemode leave
For me, I was immediately using hive command to go into hive shell after starting hadoop using start-all.sh. I re-tried using hive command after waiting for 10-20 seconds.
Might need the full path to hdfs command
/usr/local/hadoop/bin/hdfs dfsadmin -safemode leave
root# bin/hadoop fs -mkdir t
mkdir: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /user/root/t. Name node is in safe mode.
not able to create anything in hdfs
I did
root# bin/hadoop fs -safemode leave
But showing
safemode: Unknown command
what is the problem?
Solution: http://unmeshasreeveni.blogspot.com/2014/04/name-node-is-in-safe-mode-how-to-leave.html?m=1
In order to forcefully let the namenode leave safemode, following command should be executed:
bin/hadoop dfsadmin -safemode leave
You are getting Unknown command error for your command as -safemode isn't a sub-command for hadoop fs, but it is of hadoop dfsadmin.
Also after the above command, I would suggest you to once run hadoop fsck so that any inconsistencies crept in the hdfs might be sorted out.
Update:
Use hdfs command instead of hadoop command for newer distributions. The hadoop command is being deprecated:
hdfs dfsadmin -safemode leave
hadoop dfsadmin has been deprecated and so is hadoop fs command, all hdfs related tasks are being moved to a separate command hdfs.
try this, it will work
sudo -u hdfs hdfs dfsadmin -safemode leave
The Command did not work for me but the following did
hdfs dfsadmin -safemode leave
I used the hdfs command instead of the hadoop command.
Check out http://ask.gopivotal.com/hc/en-us/articles/200933026-HDFS-goes-into-readonly-mode-and-errors-out-with-Name-node-is-in-safe-mode- link too
safe mode on means (HDFS is in READ only mode)
safe mode off means (HDFS is in Writeable and readable mode)
In Hadoop 2.6.0, we can check the status of name node with help of the below commands:
TO CHECK THE name node status
$ hdfs dfsadmin -safemode get
TO ENTER IN SAFE MODE:
$ hdfs dfsadmin -safemode enter
TO LEAVE SAFE mode
~$ hdfs dfsadmin -safemode leave
If you use Hadoop version 2.6.1 above, while the command works, it complains that its depreciated. I actually could not use the hadoop dfsadmin -safemode leave because I was running Hadoop in a Docker container and that command magically fails when run in the container, so what I did was this. I checked doc and found dfs.safemode.threshold.pct in documentation that says
Specifies the percentage of blocks that should satisfy the minimal
replication requirement defined by dfs.replication.min. Values less
than or equal to 0 mean not to wait for any particular percentage of
blocks before exiting safemode. Values greater than 1 will make safe
mode permanent.
so I changed the hdfs-site.xml into the following (In older Hadoop versions, apparently you need to do it in hdfs-default.xml:
<configuration>
<property>
<name>dfs.safemode.threshold.pct</name>
<value>0</value>
</property>
</configuration>
Try this
sudo -u hdfs hdfs dfsadmin -safemode leave
check status of safemode
sudo -u hdfs hdfs dfsadmin -safemode get
If it is still in safemode ,then one of the reason would be not enough space in your node, you can check your node disk usage using :
df -h
if root partition is full, delete files or add space in your root partition and retry first step.
Namenode enters into safemode when there is shortage of memory. As a result the HDFS becomes readable only. That means one can not create any additional directory or file in the HDFS. To come out of the safemode, the following command is used:
hadoop dfsadmin -safemode leave
If you are using cloudera manager:
go to >>Actions>>Leave Safemode
But it doesn't always solve the problem. The complete solution lies in making some space in the memory. Use the following command to check your memory usage.
free -m
If you are using cloudera, you can also check if the HDFS is showing some signs of bad health. It probably must be showing some memory issue related to the namenode. Allot more memory by following the options available. I am not sure what commands to use for the same if you are not using cloudera manager but there must be a way. Hope it helps! :)
Run the command below using the HDFS OS user to disable safe mode:
sudo -u hdfs hadoop dfsadmin -safemode leave
use below command to turn off the safe mode
$> hdfs dfsadmin -safemode leave
I used following property for reduce dead node timeout.
Propertyname : dfs.heartbeat.recheck.interval
value : 1
But when I remove datanode from cluster this details not removed from hadoop cluster.It is in dead node state only in that cluster.
Please suggest any way to remove removed datanode details from hadoop cluster.
You can view the live nodes or dead nodes alone by using the below HDFS commands
hdfs dfsadmin -report -live
hdfs dfsadmin -report -dead
You can get the live node name or any other particular details using the below HDFS command
hdfs dfsadmin -report -live | grep Name:
Hope it helps.
used Sudo jps to see the daemons running. and found node manager not running.
So tried, sudo service hadoop master stop to stop and when I tried to restart it got restarted. However, when I'm giving this command hadoop dfsadmin -safemode leave its saying its deprecated. I tried this as well hadoop hdfsadmin -safemode leave
But, getting
Error: Could not find or load main class hdfsadmin
hadoop dfsadmin is depricated, however it should work. Correct usage is hdfs dfsadmin -safemode leave
hadoop dfsadmin is depricated, however it should work. Correct usage is hdfs dfsadmin -safemode leave
Safe mode is OFF
First switch from user to root and su - hdfs .
1) hdfs dfsadmin -safemode leave
Result : safe mode is OFF
I tried copying files from my local disk to hdfs . At first it gave SafeModeException. While searching for solution I read that the problem does not appear if one executes same command again. So I tried again and it didn't gave exception.
hduser#saket:/usr/local/hadoop$ bin/hadoop dfs -copyFromLocal /tmp/gutenberg/ /user/hduser/gutenberg
copyFromLocal: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /user/hduser/gutenberg. Name node is in safe mode.
hduser#saket:/usr/local/hadoop$ bin/hadoop dfs -copyFromLocal /tmp/gutenberg/ /user/hduser/gutenberg
Why is this happening?. Should I keep safemode off by using this code?
hadoop dfs -safemode leave
NameNode is in safemode until configured percent of blocks reported to be online by the data nodes. It can be configured by parameter dfs.namenode.safemode.threshold-pct in the hdfs-site.xml
For small / development clusters, where you have very few blocks - it makes sense to make this parameter lower then its default 0.9999f value. Otherwise 1 missing block can lead to system to hang in safemode.
Go to the hadoop path into bin(in my system /usr/local/hadoop/bin/),
cd /usr/local/hadoop/bin/
Check there is a file hadoop,
hadoopuser#arul-PC:/usr/local/hadoop/bin$ ls
the o/p will be,
hadoop hadoop-daemons.sh start-all.sh start-jobhistoryserver.sh stop-balancer.sh stop-mapred.sh
hadoop-config.sh rcc start-balancer.sh start-mapred.sh stop-dfs.sh task-controller
hadoop-daemon.sh slaves.sh start-dfs.sh stop-all.sh stop-jobhistoryserver.sh
Then you have to off safe mode by using command ./hadoop dfsadmin -safemode leave,
hadoopuser#arul-PC:/usr/local/hadoop/bin$ ./hadoop dfsadmin -safemode leave
you will get response as,
Safe mode is OFF
Note: I created Hadoop user with the name of hadoopuser.