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From "Nigel Daley (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-1677) improve semantics of the hadoop dfs command
Date Fri, 03 Aug 2007 17:36:53 GMT
improve semantics of the hadoop dfs command

                 Key: HADOOP-1677
                 URL: https://issues.apache.org/jira/browse/HADOOP-1677
             Project: Hadoop
          Issue Type: Improvement
          Components: dfs
            Reporter: Nigel Daley
            Priority: Minor

HADOOP-230 cover syntax changes.  Capturing here some DFS command line semantic comments between
Doug and I:

The goal for DFS should be "UNIX-like *when* possible".  The goals of HDFS are primarily to
be usable, scalable, reliable, high-performance, and, secondarily, not to be gratuitously
incompatible with UNIX.  So, when it's easy to be compatible, we certainly should.  But when
UNIX compatibility fights with one of those other goals, it may lose.

Two examples of incompatibilities with UNIX (that will need to be evaluated against the above
goal), are:

UNIX: cp foo bar succeeds if bar exists
DFS: dfs -put foo bar fails if bar exists. (same for dfs -cp).

UNIX: mkdir foo fails if foo exists
DFS: dfs -mkdir succeeds silently if foo exists and is a directory (if foo is a file than
it fails).

Many more such incompatibilities exist.

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