Unable to change the replication factor from 3 to 2

[#1]

Hi Guys,
I have been trying to change the replication factor from "3" to "2". but failed.
Here the steps :
1. First I check the replication factor from Ambari server. it is "3".
2. Then i go to shell and check the replication factor by wrote the commands :
"cd /etc/hadoop/conf" :

"View hdfs-site.xml"
replication factor is "3" also here.
3. Then i go to Ambari server and Change the replication factor from "3" to "2" and final it by click the "Lock" button and then Save.
4. and then i have restart the all services.
after these steps Ambari server show me replication factor "2" . BUT when i go to shell and write the command :
"View hdfs-site.xml"
it show me replication factor still "3" .
What thing i did wrong ?
Thanks

[#2 · Accepted solution]

Hi @Mudassar Hussain

Did you put namenode safemode and save the namespace?

sudo su hdfs -l -c 'hdfs dfsadmin -safemode enter'
sudo su hdfs -l -c 'hdfs dfsadmin -saveNamespace'

restart sevices and see hdfs-site.xml

cat /etc/hadoop/conf/hdfs-site.xml
<property>
 <name>dfs.replication</name>
 <value>2</value>
</property>

You can also check that Ambari Dashboard HDFS Disk Usage is decreased.

[#3]

Thanks @Erkan ŞİRİN
when i write the above command it give me an error. Please see the image :

and is it right that Replication-Factor change effect apply on new file not on old file ?

[#4]

Hi, please give the command with root user.

[root@namenode~]# sudo su hdfs -l -c 'hdfs dfsadmin -safemode enter'
[root@namenode~]# sudo su hdfs -l -c 'hdfs dfsadmin -saveNamespace'

[#5]

Thanks a lot @Erkan ŞİRİN this works 🙂
Now how i put the @NameNode into "Normal Mode" ?
and what the reason to put the @namenode in safeMode ?

[#6]

Thanks a lot @Erkan ŞİRİN it works 🙂 How i put the @namenode into normal mode ? and what is the reason to put the @namenode into safe mode ?

[#7]

It is because the way how namenode works. It merges namespace repo (fsimage) periodically with edit logs file. To prevent namespace inconsistency it stops changing namespace by entering safemode.

hdfs dfsadmin -safemode leave

should work.