Setting file system Permissions
The Data Fabric file system permissions are similar to the POSIX permissions model. Each file and directory is associated with a user (the owner) and a group. You can set read, write, and execute permissions separately for:
- the owner of the file or directory.
- members of the group associated with the file or directory.
- all other users.
The permissions for a file or directory are called its mode. The mode of a file or directory can be expressed in two ways:
- Text - a string that indicates the presence of the read
(
r), write (w), and execute (x) permission or their absence (-) for the owner, group, and other users respectively. Example:rwxr-xr-x - Octal - three octal digits (for the owner, group, and other users),
that use individual bits to represent the three permissions. Example:
755
Both rwxr-xr-x and 755 represent the same mode; the owner
has all permissions, and the group and other users have read and execute permissions
only.
When you access the file system layer
over NFS, the file-level permissions are controlled through the Linux
interface by using the chmod (change mode) command or the
chown (change owner) command, as well as the hadoop fs
-chmod and hadoop fs -chown equivalents. For example:
chown jsmith /mapr/my.cluster.com/jsmith/fileA
hadoop -fs chown jsmith /mapr/my.cluster.com/jsmith/fileA
chmod 744 /mapr/my.cluster.com/jsmith/fileA
hadoop -fs chmod 744 /mapr/my.cluster.com/jsmith/fileAThese commands grant a user whose username is
jsmith the read, write, and execute privileges on
fileA.
Once you set file permissions, authorization checks are performed when a file is opened, and on every file access.