Chapter 20. Stackable VFS modules
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## Chapter 20. Stackable VFS modules

### Jelmer R. Vernooij

The Samba Team

`<jelmer@samba.org>`

### John H. Terpstra

Samba Team

`<jht@samba.org>`

### Tim Potter

Samba Team

`<tpot@samba.org>`

### Simo Sorce

original vfs_skel README

### Alexander Bokovoy

original vfs_netatalk docs

### Stefan Metzmacher

Update for multiple modules

## 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 through 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 compiling 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 objects parameter where you can list one or more VFS modules by name. For example, to log all access to files and put deleted files in a recycle bin, see next configuration:

Example 20.1. smb.conf with VFS modules

`[audit]`
`comment = Audited /data directory`
`path = /data`
`vfs objects = audit recycle`
`writeable = yes`
`browseable = yes`

The modules are used in the order in which they are specified. Let's say that you want to both have a virus scanner module and a recycle bin module. It is wise to put the virus scanner module as the first one so that it is the first that get run an may detect a virus immediately, before any action is performed on that file. vfs objects = vscan-clamav recycle

Samba will attempt to load modules from the `/lib` directory in the root directory of the Samba installation (usually `/usr/lib/samba/vfs` or `/usr/local/samba/lib/vfs` ).

Some modules can be used twice for the same share. This can be done using a configuration similar to the one shown in the following example.

Example 20.2. smb.conf with multiple VFS modules

`[test]`
`comment = VFS TEST`
`path = /data`
`writeable = yes`
`browseable = yes`
`vfs objects = example:example1 example example:test`
`example1: parameter = 1`
`example: parameter = 5`
`test: parameter = 7`

## 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 files. The log level for this module is set in the `smb.conf` file.

Valid settings and the information that will be recorded are shown in the next table.

Table 20.1. Extended Auditing Log Information

Log Level | Log Details - File and Directory Operations
--- | ---
0 | Creation / Deletion
1 | Create / Delete / Rename / Permission Changes
2 | Create / 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, 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. Where used, unlink calls will be intercepted and files moved to the recycle directory instead of being deleted. This gives the same effect as the Recycle Bin on Windows computers.

The Recycle Bin will not appear in Windows Explorer views of the network file system (share) nor on any mapped drive. Instead, a directory called `.recycle` will be automatically created when the first file is deleted. Users can recover files from the `.recycle` directory. If the `recycle:keeptree` has been specified, deleted files will be found in a path identical with that from which the file was deleted.

Supported options for the recycle module are as follow:

recycle:repository

  Relative path of the directory where deleted files should be moved.

recycle:keeptree

  Specifies whether the directory structure should be kept or if the files in the directory that is being deleted should be kept separately in the recycle bin.

recycle:versions

  If this option is set, two files with the same name that are deleted will both be kept in the recycle bin. Newer deleted versions of a file will be called “Copy #x of `filename`”.

recycle:touch

  Specifies whether a file's access date should be touched when the file is moved to the recycle bin.

recycle:maxsize

  Files that are larger than the number of bytes specified by this parameter will not be put into the recycle bin.

recycle:exclude

  List of files that should not be put into the recycle bin when deleted, but deleted in the regular way.

recycle:exclude_dir

  Contains a list of directories. When files from these directories are deleted, they are not put into the recycle bin but are deleted in the regular way.

recycle:noversions

  Opposite of `recycle:versions`. If both options are specified, this one takes precedence.

### netatalk

A netatalk module will ease co-existence of Samba and netatalk file sharing services.

Advantages compared to the old netatalk module:

- Does not care about creating .AppleDouble forks, just keeps them in sync.

- If a share in `smb.conf` does not 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 do not 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 that 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,” and so on. I have since easily applied it to a student roster database.) 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, and so on. 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 course, Samba has to be compiled with VFS support. `samba-vscan` supports various virus scanners and is maintained by Rainer Link.

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