[jira] [Resolved] (HDFS-3074) HDFS ignores group of a user when creating a file or a directory, and instead inherits

["Todd Lipcon (Resolved) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-3074?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon resolved HDFS-3074.
-------------------------------

    Resolution: Won't Fix

For whatever strange historic reason, Hadoop uses BSD semantics instead of Linux semantics for group ownership at creation. I filed this "bug" once, too :)
                
> HDFS ignores group of a user when creating a file or a directory, and instead inherits
> --------------------------------------------------------------------------------------
>
>                 Key: HDFS-3074
>                 URL: https://issues.apache.org/jira/browse/HDFS-3074
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.23.1
>            Reporter: Harsh J
>            Priority: Minor
>
> When creating a file or making a directory on HDFS, the namesystem calls pass {{null}} for the group name, thereby having the parent directory permissions inherited onto the file.
> This is not how the Linux FS works at least.
> For instance, if I have today a user 'foo' with default group 'foo', and I have my HDFS home dir created as "foo:foo" by the HDFS admin, all files I create under my directory too will have "foo" as group unless I chgrp them myself. This makes sense.
> Now, if my admin were to change my local accounts' default/primary group to 'bar' (but did not change so on my homedir on HDFS, and I were to continue writing files to my home directory or any subdirectory that has 'foo' as group, all files still get created with group 'foo' - as if the NN has not realized the primary group of the mapped shell account has already changed.
> On linux this is the opposite. My login session's current primary group is what determines the default group on my created files and directories, not the parent dir owner.
> If the create and mkdirs call passed UGI's group info (UserGroupInformation.getCurrentUser().getGroupNames()[0] should give primary group?) along into their calls instead of a null in the PermissionsStatus object, perhaps this can be avoided.
> Or should we leave this as-is, and instead state that if admins wish their default groups of users to change, they'd have to chgrp all the directories themselves?

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