Chapter 20. Stackable VFS modules

Jelmer R. Vernooij

The Samba Team

John H. Terpstra

Samba Team

Alexander Bokovoy

Tim Potter

Simo Sorce

Table of Contents

Features and Benefits
Discussion
Included modules
audit
extd_audit
fake_perms
recycle
netatalk
VFS modules available elsewhere
DatabaseFS
vscan
Common Errors

Features and Benefits

Since Samba-3, there is support for stackable VFS(Virtual File System) modules. Samba passes each request to access the unix file system thru the loaded VFS modules. This chapter covers all the modules that come with the samba source and references to some external modules.

Discussion

If not supplied with your platform distribution binary Samba package you may have problems to compile these modules, as shared libraries are compiled and linked in different ways on different systems. They currently have been tested against GNU/Linux and IRIX.

To use the VFS modules, create a share similar to the one below. The important parameter is the vfs object parameter which must point to the exact pathname of the shared library objects. For example, to log all access to files and use a recycle bin:
[audit]
	comment = Audited /data directory
    path = /data
    vfs object = /path/to/audit.so /path/to/recycle.so
    writeable = yes
    browseable = yes

The modules are used in the order they are specified.

Further documentation on writing VFS modules for Samba can be found in the Samba Developers Guide.

Included modules

audit

A simple module to audit file access to the syslog facility. The following operations are logged:
share
connect/disconnect
directory opens/create/remove
file open/close/rename/unlink/chmod

extd_audit

This module is identical with the audit module above except that it sends audit logs to both syslog as well as the smbd log file/s. The loglevel for this module is set in the smb.conf file.

The logging information that will be written to the smbd log file is controlled by the log level parameter in smb.conf. The following information will be recorded:

Table 20.1. Extended Auditing Log Information

Log LevelLog Details - File and Directory Operations
0Creation / Deletion
1Create / Delete / Rename / Permission Changes
2Create / Delete / Rename / Perm Change / Open / Close

fake_perms

This module was created to allow Roaming Profile files and directories to be set (on the Samba server under Unix) as read only. This module will if installed on the Profiles share will report to the client that the Profile files and directories are writable. This satisfies the client even though the files will never be overwritten as the client logs out or shuts down.

recycle

A recycle-bin like module. When used any unlink call will be intercepted and files moved to the recycle directory instead of being deleted.

Supported options:
vfs_recycle_bin:repository

FIXME

vfs_recycle_bin:keeptree

FIXME

vfs_recycle_bin:versions

FIXME

vfs_recycle_bin:touch

FIXME

vfs_recycle_bin:maxsize

FIXME

vfs_recycle_bin:exclude

FIXME

vfs_recycle_bin:exclude_dir

FIXME

vfs_recycle_bin:noversions

FIXME

netatalk

A netatalk module, that will ease co-existence of samba and netatalk file sharing services.

Advantages compared to the old netatalk module:
it doesn't care about creating of .AppleDouble forks, just keeps them in sync
if a share in smb.conf doesn't contain .AppleDouble item in hide or veto list, it will be added automatically

VFS modules available elsewhere

This section contains a listing of various other VFS modules that have been posted but don't currently reside in the Samba CVS tree for one reason or another (e.g. it is easy for the maintainer to have his or her own CVS tree).

No statements about the stability or functionality of any module should be implied due to its presence here.

DatabaseFS

URL: http://www.css.tayloru.edu/~elorimer/databasefs/index.php

By Eric Lorimer.

I have created a VFS module which implements a fairly complete read-only filesystem. It presents information from a database as a filesystem in a modular and generic way to allow different databases to be used (originally designed for organizing MP3s under directories such as "Artists," "Song Keywords," etc... I have since applied it to a student roster database very easily). The directory structure is stored in the database itself and the module makes no assumptions about the database structure beyond the table it requires to run.

Any feedback would be appreciated: comments, suggestions, patches, etc... If nothing else, hopefully it might prove useful for someone else who wishes to create a virtual filesystem.

vscan

URL: http://www.openantivirus.org/

samba-vscan is a proof-of-concept module for Samba, which uses the VFS (virtual file system) features of Samba 2.2.x/3.0 alphaX. Of couse, Samba has to be compiled with VFS support. samba-vscan supports various virus scanners and is maintained by Rainer Link.

Common Errors

There must be some gotchas we should record here! Jelmer???