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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6165) "hdfs dfs -rm -r" is slightly different from the Unix "rm -r" for deleting an empty directory
Date Sun, 30 Mar 2014 22:00:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6165?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13954846#comment-13954846
] 

Yongjun Zhang commented on HDFS-6165:
-------------------------------------

Hi [~cnauroth], 

I revisited your comments at -28/Mar/14 16:47 and studied the POSIX spec,  and understood
your points better.

{quote}
rm: If the current file is a directory, rm shall perform actions equivalent to the rmdir()
...

The rmdir() function shall fail if:
[EACCES]
 Search permission is denied on a component of the path prefix, or write permission is denied
on the parent directory of the directory to be removed.
{quote}

As you pointed out, there is mention of permission on the component of the path prefix, but
there is no mention of permission on the directory to be removed.  What it meant seems to
be "empty dir's permission can be ignored" when other permissions described in the above quote
are satisfied. 
And my experiments show that the CentOs implementation does that. 

Maybe  the test results [~daryn] got on his Mac is also a "nicety of the shell utility" on
mac: it checks the read permission of dir even though it's empty.

I looked at "Advanced Programming in the UNIX Environment" textbook written by W. Richard
Stevens, it says:
{quote}
To delete an existing file, we need write permission and execute permission in the directory
containing the file, We do not need read permission or write permission for the file itself.
{quote}
He talks about delete existing file, but not existing directory.

The link I found http://wiki.dreamhost.com/Unix_File_Permissions says
{quote}
For a directory, ..., Write ("w") means that the grantee has permission to create new files
within that directory and to delete the directory (when empty).
{quote}

I wonder whether we should also ignore the empty dir's permissions in this case in HDFS.

Thanks you all again.



> "hdfs dfs -rm -r" is slightly different from the Unix "rm -r" for deleting an empty directory
> ---------------------------------------------------------------------------------------------
>
>                 Key: HDFS-6165
>                 URL: https://issues.apache.org/jira/browse/HDFS-6165
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.3.0
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>            Priority: Minor
>         Attachments: HDFS-6165.001.patch, HDFS-6165.002.patch, HDFS-6165.003.patch
>
>
> Given a directory owned by user A with permissions 0700 containing an empty directory
owned by user B, it is not possible to delete user B's directory. This is incorrect. Write
permission on the containing directory should be all that is needed to delete the child directory.
Here's a reproduction:
> {code}
> [root@vm01 ~]# hdfs dfs -ls /user/
> Found 4 items
> drwxr-xr-x   - userabc users               0 2013-05-03 01:55 /user/userabc
> drwxr-xr-x   - hdfs    supergroup          0 2013-05-03 00:28 /user/hdfs
> drwxrwxrwx   - mapred  hadoop              0 2013-05-03 00:13 /user/history
> drwxr-xr-x   - hdfs    supergroup          0 2013-04-14 16:46 /user/hive
> [root@vm01 ~]# hdfs dfs -ls /user/userabc
> Found 8 items
> drwx------   - userabc users          0 2013-05-02 17:00 /user/userabc/.Trash
> drwxr-xr-x   - userabc users          0 2013-05-03 01:34 /user/userabc/.cm
> drwx------   - userabc users          0 2013-05-03 01:06 /user/userabc/.staging
> drwxr-xr-x   - userabc users          0 2013-04-14 18:31 /user/userabc/apps
> drwxr-xr-x   - userabc users          0 2013-04-30 18:05 /user/userabc/ds
> drwxr-xr-x   - hdfs    users          0 2013-05-03 01:54 /user/userabc/foo
> drwxr-xr-x   - userabc users          0 2013-04-30 16:18 /user/userabc/maven_source
> drwxr-xr-x   - hdfs    users          0 2013-05-03 01:40 /user/userabc/test-restore
> [root@vm01 ~]# hdfs dfs -ls /user/userabc/foo/
> [root@vm01 ~]# sudo -u userabc hdfs dfs -rm -r -skipTrash /user/userabc/foo
> rm: Permission denied: user=userabc, access=ALL, inode="/user/userabc/foo":hdfs:users:drwxr-xr-x
> {code}
> The super user can delete the directory.
> {code}
> [root@vm01 ~]# sudo -u hdfs hdfs dfs -rm -r -skipTrash /user/userabc/foo
> Deleted /user/userabc/foo
> {code}
> The same is not true for files, however. They have the correct behavior.
> {code}
> [root@vm01 ~]# sudo -u hdfs hdfs dfs -touchz /user/userabc/foo-file
> [root@vm01 ~]# hdfs dfs -ls /user/userabc/
> Found 8 items
> drwx------   - userabc users          0 2013-05-02 17:00 /user/userabc/.Trash
> drwxr-xr-x   - userabc users          0 2013-05-03 01:34 /user/userabc/.cm
> drwx------   - userabc users          0 2013-05-03 01:06 /user/userabc/.staging
> drwxr-xr-x   - userabc users          0 2013-04-14 18:31 /user/userabc/apps
> drwxr-xr-x   - userabc users          0 2013-04-30 18:05 /user/userabc/ds
> -rw-r--r--   1 hdfs    users          0 2013-05-03 02:11 /user/userabc/foo-file
> drwxr-xr-x   - userabc users          0 2013-04-30 16:18 /user/userabc/maven_source
> drwxr-xr-x   - hdfs    users          0 2013-05-03 01:40 /user/userabc/test-restore
> [root@vm01 ~]# sudo -u userabc hdfs dfs -rm -skipTrash /user/userabc/foo-file
> Deleted /user/userabc/foo-file
> {code}



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