In manner of providing a quick byte, /tmp folder( check hadoop.tmp.dir) is only temporarily used by MR process and they are ideally cleaned up after the job has finished execution on cleanup/abort. MR is a process which loads/stores data in HDFS. Most of your queries relate to knowing your default hdfs location. You can find that by "hadoop dfs -ls".The path preceding .Trash is your default hdfs location.
HTH, / On 4/5/10 4:24 PM, "psdc1978" <[email protected]> wrote: Hi, When I run an MapReduce example, I've noticed that some temporary directories are buit in /tmp directory. In my case, in the /tmp/hadoop directory it was created the following file directory during the execution of wordcount example: job_201004041803_0002/ |-- attempt_201004041803_0002_m_000000_0_0_m_0 | |-- job.xml | |-- output | | |-- file.out | | `-- file.out.index | |-- pid | `-- split.dta 1 - In the map attempt task it exists a file.out and split.dta file.The split.dta is the map output produced by the map and that will be fetched by the reducer? 2 - What's the file.out and file.out.index? 3 - Is this data were written by MR anything related to HDFS? 4 - I'm a bit confused to differentiate between the files that are written in /tmp directory during the execution of my example, and the place where the files are written with the command "bin/hadoop dfs -copyFromLocal". a) When I execute the "bin/hadoop dfs -copyFromLocal <from> <to>" command, where's the destination folder? b) Is it in memory or is physically in my HD? c) If the files are written in the HD, in wich directory are they? d) What is the difference between the data written win the command -copyFromLocal and the data written in the /tmp directory? 5 - The output of a reducer example comes in the form part_0000 that is written in gutenberg-output. Where is this file? Is it in my HD? Thank you,
