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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-245) Create symbolic links in HDFS
Date Thu, 24 Sep 2009 23:08:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12759312#action_12759312
] 

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

bq.(From the lstat(2) man page: "Unlike other filesystem objects, symbolic links do not have
an owner, group, access mode, times, etc. Instead, these attributes are taken from the directory
that contains the link. The only attributes returned from an lstat() that refer to the symbolic
link itself are the file type (S_IFLNK), size, blocks, and link count (always 1)." 

Danger! lstat() implementations differ between the various flavors! IEEE Std 1003.1, 2004
[http://www.opengroup.org/onlinepubs/009695399/functions/lstat.html] says:

{quote}
The lstat() function shall be equivalent to stat(), except when path refers to a symbolic
link. In that case lstat() shall return information about the link, while stat() shall return
information about the file the link references.
{quote}



> 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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