16.1 Features and Benefits

The Distributed File System (DFS) provides a means of separating the logical view of files and directories that users see from the actual physical locations of these resources on the network. It allows for higher availability, smoother storage expansion, load balancing, and so on.

For information about DFS, refer to the Microsoft documentation ^[1] . This document explains how to host a DFS tree on a UNIX machine (for DFS-aware clients to browse) using Samba.

^[1] http://www.microsoft.com/NTServer/nts/downloads/winfeatures/NTSDistrFile/AdminGuide.asp

To enable SMB-based DFS for Samba, configure it with the --with- msdfs option. Once built, a Samba server can be made a DFS server by setting the global Boolean host msdfs parameter in the smb.conf file. You designate a share as a DFS root using the Share Level Boolean msdfs root parameter. A DFS root directory on Samba hosts DFS links in the form of symbolic links that point to other servers. For example, a symbolic link junction->msdfs:storage1\share1 in the share directory acts as the DFS junction. When DFS-aware clients attempt to access the junction link, they are redirected to the storage location (in this case, \\storage1\share1 ).

DFS trees on Samba work with all DFS-aware clients ranging from Windows 95 to 200x. Example 16.1 shows how to setup a DFS tree on a Samba server. In the /export/dfsroot directory, you set up your DFS links to other servers on the network.

 root# cd /export/dfsroot root# chown root /export/dfsroot root# chmod 755 /export/dfsroot root# ln -s msdfs:storageA\\shareA linka root# ln -s msdfs:serverB\\share,serverC\\share linkb 

Example 16.1 smb.conf with DFS configured

  [global]   netbios name = GANDALF   host msdfs = yes   [dfs]   path = /export/dfsroot   msdfs root = yes  

You should set up the permissions and ownership of the directory acting as the DFS root so that only designated users can create, delete or modify the msdfs links. Also note that symlink names should be all lowercase. This limitation exists to have Samba avoid trying all the case combinations to get at the link name. Finally, set up the symbolic links to point to the network shares you want and start Samba.

Users on DFS-aware clients can now browse the DFS tree on the Samba server at \\samba\dfs. Accessing links linka or linkb (which appear as directories to the client) takes users directly to the appropriate shares on the network.