Is there any way to change the replication of files on HDFS after they are already written to HDFS?

Hadoop - Interview Questions

Yes, the following are ways to change the replication of files on HDFS :

We can change the dfs.replication value to a particular number in the $HADOOP_HOME/conf/hadoop-site.xml file, which will start replicating to the factor of that number for any new content that comes in.

If you want to change the replication factor for a particular file or directory, use :

$HADOOP_HOME/bin/Hadoop dfs –setrep –w4 /path of the file

Example : $HADOOP_HOME/bin/Hadoop dfs –setrep –w4 /user/temp/test.csv