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Date: Thu, 24 Sep 2009 10:23:16 -0700 (PDT)
From: "Allen Wittenauer (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-245) Create symbolic links in HDFS
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    [ https://issues.apache.org/jira/browse/HDFS-245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12759184#action_12759184 ] 

Allen Wittenauer commented on HDFS-245:
---------------------------------------

bq. What is the new options for fsck to report dangling links? What does the output look like?

Why should fsck report this at all?  Since symlinks take the form of a URL, fsck would need to make call outs to a potentially remote system to verify.  Over a large file system with many symlinks, this could be a tremendous amount of network bandwidth.  IIRC, no other OS has a "report all broken symlinks" functionality.  The reality is, is that very few symlinks are "important" enough to have that much scrutiny. Instead, there is a  reliance upon savvy admins to write scripts using find to locate symlinks and verify.  [But since we have no find ... ]

bq. access control properties of links are ignored, checks are always performed against the link target (if it resides in an HDFS file system). The ch* operations should operate directly on the target.

I disagree. We need chown -h (POSIX) and  chown -H, chown -L, and chown -P (SVID?) for the same reasons that those OSes support them.

We also need test -h and test -L supported.

> Create symbolic links in HDFS
> -----------------------------
>
>                 Key: HDFS-245
>                 URL: https://issues.apache.org/jira/browse/HDFS-245
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: 4044_20081030spi.java, designdocv1.txt, HADOOP-4044-strawman.patch, symlink-0.20.0.patch, symLink1.patch, symLink1.patch, symLink11.patch, symLink12.patch, symLink13.patch, symLink14.patch, symLink15.txt, symLink15.txt, symlink16-common.patch, symlink16-hdfs.patch, symlink16-mr.patch, symlink17-common.txt, symlink17-hdfs.txt, 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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