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A HDFS directory, when seen in Cloudera Hue, appears to have the following permission flags:
drwxrwxrwxt
I understand that it is a directory (d), that can be used in read/write mode (rw) by all users and that all users can access the children (x).
What does the last flag t mean ?
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Similarly, the HDFS file system also implements a set of permissions, for this Owner, Group, and Others. In Linux we use -rwx for permission to the specific user where r is read, w is for write or append and x is for executable.
The file or directory has separate permissions for the user that is the owner, for other users that are members of the group, and for all other users. For files, the r permission is required to read the file, and the w permission is required to write or append to the file.
Changing HDFS File Permissions You must be a super user or the owner of a file or directory to change its permissions. With the chgrp, chmod and chown commands you can specify the –R option to make recursive changes through the directory structure you specify.
The t flag is called a sticky bit. A sticky bit is a permission bit that is set on a directory that allows only the owner of the file within that directory or the root user to delete or rename the file. No other user has the needed privileges to delete the file created by some other user.
This is a security measure to avoid deletion of critical folders and their content (sub-directories and files), though other users have full permissions.
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