What is hadoop.tmp.dir ?

Question

As per documentation, hadoop.tmp.dir is `"A base for other temporary directories." I presume, this path refers to a local file system.

I set this value to /mnt/Hadoop-tmp/hadoop-${user.name}. After formatting the namenode and starting all services, I see the same path created on HDFS.

Does this mean, hadoop.tmp?dir refers to a temporary location on HDFS?

Answer 1

hadoop.tmp.dir act as the base for temporary directories locally, and also in HDFS.

The mapred.system.dir is by default put in to "$/mapred/system", and this describes the path on the HDFS where the Map/Reduce framework stores system files.

If you need these to not be tied together, you can edit your mapred-site.xml such that the definition of mapred.system.dir is something that's not tied to ${hadoop.tmp.dir}