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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4044) Create symbolic links in HDFS
Date Mon, 06 Oct 2008 17:37:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12637147#action_12637147

Doug Cutting commented on HADOOP-4044:

> I prefer the name symlink instead of link.

Hmm.  'Symbolic link' is the marked case in unix, the exception, where 'link' alone refers
to a hard link.  The reason is historic, symbolic links were not added to unix until 4.2 BSD.
 The term 'link' was already used to describe hard links and so had to be qualified, even
though symbolic links are now more commonly used than hard links.  In Hadoop I argue we should
make hard links the marked case, and that the default understanding of 'link' in Hadoop, as
on the web, should be like unix's symbolic link.  If we ever add support for hard links, then
they would become the marked case in Hadoop, requiring qualification, like server-side redirects.
 However I would not veto this if the majority prefer a longer name here.

> the method next() suggests that one follows the path to the next symbolic link. It does
not strictly.

Can you elaborate?  Each time this is called a link is resolved, returning a path that may
contain more links, following a chain of links, no?  Also, 'doOperation()' is next to meaningless.
 So if 'next' is indeed inappropriate we should replace it with something more specific, not
something generic.

> 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, symLink1.patch, symLink4.patch, symLink5.patch,
symLink6.patch, symLink8.patch, symLink9.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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