Monday, May 28, 2012

Hadoop: "Format aborted" Error Message

I have recently started playing around with hadoop. I went through a bunch of tutorials and docs and installed it on a Centos 6 box. When I tried to start the namenode, it gave me an error informing that my namenode dir is not formatted. Fair enough but whenever I tried to format it, it used to get aborted. I checked all the configs, user, group, permissions and what not. I read and reread the docs to figure out if I am missing anything but no luck. Every time I got the following error:

-bash-4.1$ hadoop namenode -format
12/05/28 07:33:42 INFO namenode.NameNode: STARTUP_MSG:
STARTUP_MSG: Starting NameNode
STARTUP_MSG:   host =
STARTUP_MSG:   args = [-format]
STARTUP_MSG:   version = 0.20.2-cdh3u4
STARTUP_MSG:   build = file:///data/1/tmp/topdir/BUILD/hadoop-0.20.2-cdh3u4 -r 214dd731e3bdb687cb55988d3f47dd9e248c5690; compil
ed by 'root' on Mon May  7 14:01:59 PDT 2012
Re-format filesystem in /data/namenode ? (Y or N) y
Format aborted in /data/namenode
12/05/28 07:33:46 INFO namenode.NameNode: SHUTDOWN_MSG:
SHUTDOWN_MSG: Shutting down NameNode at

There were no logs or messages to analyze. Every things looked in order then what was the issue?

Turned out that when the CLI asked me "Re-format filesystem in /data/namenode ? (Y or N)" I was supposed to hit upper case Y and not y. I found this quite bad and un-intuitive on developers' part that they did not implement case-insensitivity or gave out a message about hitting upper case when a lower case was entered. I just hope that this post might save someone some time.


  1. Thank you for posting this. I had the exact same problem.

  2. Oh God, I spent one day trying to figure this out... Thanks!

  3. Had the same problem, thanks for the post!

  4. thank you so much! i was going nuts. would've never figured that out.

  5. You've got to be kidding me, why didn't the developers just add half a line of code? I also spent a few hours on this. Thanks for the fix!

  6. Thanks mate, I facepalmed myself after reading this.