question Re: Namenode safe mode in Archives of Support Questions (Read Only)

Namenode safe mode

sreeviswa_athic — Tue, 14 Mar 2017 07:11:55 GMT

During maintenance of Cluster, we put Namenode into Safemode.

How to identify if Namenode is in safemode. I mean is there a command which tells us if Namenode is in safemode. Or what are the characteristics that determine Namenode is under Safe mode

Re: Namenode safe mode

sunile_manjee — Tue, 14 Mar 2017 07:14:40 GMT

Run hadoop dfsadmin -safemode get

[LAKE] [xxx@lake1 ~]# hadoop dfsadmin -safemode get
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.


Safe mode is OFF in xx.xx.xx.com/1xxxx5:8020
Safe mode is OFF in xx.xx.xx.com/1xxx:8020
[LAKE] [xxx@lake1 ~]#

Re: Namenode safe mode

namaheshwari — Tue, 14 Mar 2017 13:27:34 GMT

As per the documentation:

https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.3.0-Win/bk_HDP_Install_Win/content/ref-d4ba8d91-cfe7-4655-8181-0168cc6d2681.1.html

Safemode: Safemode is a state where no changes can be made to the blocks. HDFS cluster is in safemode state during start up because the cluster needs to validate all the blocks and their locations. Once validated, safemode is then disabled.

The options for safemode command are:

hdfs dfsadmin -safemode [enter | leave | get]

Please see the following commands:

root@mycluster:~# su - hdfs
hdfs@mycluster:~$ hdfs dfsadmin -safemode enter
Safe mode is ON
hdfs@mycluster:~$ hdfs dfsadmin -safemode get
Safe mode is ON
hdfs@mycluster:~$ hdfs dfsadmin -safemode leave
Safe mode is OFF
hdfs@mycluster:~$

Re: Namenode safe mode

rajsyrus — Tue, 14 Mar 2017 17:00:50 GMT

@Viswa

To check Namenode Safe mode status, Login to Namenode host and issue the below command,

[user@NNhost1 ~]$ hdfs dfsadmin -safemode get 
Safe mode is OFF in NNhost1/10.X.X.X:8020 
Safe mode is OFF in NNhost2/10.X.X.X:8020

If Safe mode is turned ON, please issue the below command to leave from safemode.
[user@NNhost1 ~]$ hdfs dfsadmin -safemode leave