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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4044) Create symbolic links in HDFS
Date Wed, 10 Sep 2008 22:36:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12630015#action_12630015

dhruba borthakur commented on HADOOP-4044:

I would like to propose that the symbolic links point only to files (and not to directories).
Why this restriction:

1. Symbolic links that point to directories are more like mount-points.
2. My current use-case (HADOOP-4058) does not require symbolic links to point to directories.
3. Directories in HDFS are more like object-references to file(s), they do not yet have all
POSIX semantics associated with them. The clients do not parse components of the directory
path, instead sends the entire pathname to the server for a lookup.
4. Avoiding symbolic links that point to directories keeps the code simple (till we really
need it). An open(/foo/bar/zoo) where bar is a symbolic link does not arise.

In this proposal, a symbolic link can still be relative or absolute. No kickback (via exception
or otherwise) is needed to implement this proposal. Also, this proposal does not preclude
implementing the "symbolic links to directories" in the future.

> Create symbolic links in HDFS
> -----------------------------
>                 Key: HADOOP-4044
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4044
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: symLink1.patch
> HDFS should support symbolic links. A symbolic link is a special type of file that contains
a reference to another file or directory in the form of an absolute or relative path and that
affects pathname resolution. Programs which read or write to files named by a symbolic link
will behave as if operating directly on the target file. However, archiving utilities can
handle symbolic links specially and manipulate them directly.

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