Filesystem Operations on MapR-DB Tables
The MapR file system stores tables in the same namespace as files. You can move and delete
tables in much the same way as you can with files. All file system operations remain
accessible with the hadoop fs
command.
Volume properties, such as replication factor or rack topology, that apply to the specified
location also apply to tables stored at that location. You can move a table with the Linux
mv
command or the hadoop fs -mv
command.
When you use Direct Access NFS or the hadoop fs -ls
command to access a
MapR cluster, tables and files are listed together. Because the client's Linux commands are
not table-aware, other Linux file manipulation commands, notably file read and write
commands, are not available for MapR-DB tables.
This section describes the operations that you can perform on MapR-DB tables through a
Linux command line when you access the cluster through NFS or with the hadoop
fs
commands.
Setting Permissions
MapR-DB tables do not support setting user permissions through the UNIX
chmod
command or the hadoop fs -chmod
analogue.
Instead, MapR-DB table access is controlled with Access Control Expressions (ACEs). See
Enabling Table Authorizations with Access Control Expressions.
Read and Write
You cannot perform read or write operations on a MapR-DB table from a Linux file system
context. For example, you cannot use the cat
command to view the
content of a table or search through a table with the grep
command. MFS
returns an error when an application attempts to read or write to a MapR-DB table.
Move
You can move a MapR-DB table within a volume with the mv
command over
NFS or with the hadoop fs -mv
command. These moves are subject to the
standard permissions restrictions. Moves across volumes are not currently supported.
Remove
You can remove a table with the rm
command over NFS or with the
hadoop fs -rm
command. These commands remove the table from the
namespace and asynchronously reclaims the disk space. You can remove a directory that
includes both files and tables with the rm -r
or hadoop fs
-rmr
commands.
Copy and Recursive/Directory Copy
Table copying at the file-system level is not supported. See Migrating Between Apache HBase Tables and MapR-DB Tables for information on copying tables using the HBase shell.