Software Update: Samba 4.2.0

Version 4.2 of Samba has been released. This program runs on Unix, BSD and Linux servers, and is an open source implementation of the smb/cifsnetwork protocol† Since version 3, Samba can offer file and print services to Windows clients and is able to act as a domain controller. Extensive documentation, including practical how-tos for a slightly older version, can be found at this page are being found. With this release, support for version 3 of Samba has officially ended. The most important changes in version 4.2 are listed below.

Transparent File Compression
Samba 4.2.0 adds support for the manipulation of file and folder compression flags on the Btrfs filesystem. With the Btrfs Samba VFS module enabled, SMB2+ compression flags can be set remotely from the Windows Explorer File->Properties->Advanced dialog. Files flagged for compression are transparently compressed and uncompressed when accessed or modified.

Previous File Versions with Snapper
The newly added Snapper VFS module exposes snapshots managed by Snapper for use by Samba. This provides the ability for remote clients to access shadow-copies via Windows Explorer using the “previous versions” dialog.

Winbindd/Netlogon improvements
The whole concept of maintaining the netlogon secure channel to (other) domain controllers was rewritten in order to maintain global state in a netlogon_creds_cli.tdb. This is the proper fix for a large number of bugs:

In addition a strong session key is now required by default, which means that communication to older servers or clients might be rejected by default.

For the client side we have the following new options: “require strong key” (yes by default), “reject md5 servers” (no by default). Eg for Samba 3.0.37 you need “require strong key = no” and for NT4 DCs you need “require strong key = no” and “client NTLMv2 auth = no”,

On the server side (as domain controller) we have the following new options: “allow nt4 crypto” (no by default), “reject md5 client” (no by default). Eg in order to allow Samba Winbindd use on the Samba AD DC
Winbindd is now used on the Samba AD DC by default, replacing the partial rewrite used for winbind operations in Samba 4.0 and 4.1.

This allows more code to be shared, more options to be honored, and paves the way for support for trusted domains in the AD DC.

If required the old internal winbind can be activated by setting ‘server services = +winbind -winbindd’. Upgrading users with a server services parameter specified should ensure they change ‘winbind’ to ‘winbindd’ to obtain the new functionality.

The ‘samba’ binary still manages the starting of this service, there is no need to start the winbindd binary manually.

Winbind now requires secured connections
To improve protection against rogue domain controllers we now require that when we connect to an AD DC in our forest, that the connection be signed using SMB Signing. Set ‘client signing = off’ in the smb.conf to disable.

Also and DCE/RPC pipes must be sealed, set ‘require strong key = false’ and ‘winbind sealed pipes = false’ to disable.

Finally, the default for ‘client ldap sasl wrapping’ has been set to ‘sign’, to ensure the integrity of LDAP connections. Set ‘client ldap sasl wrapping = plain’ to disable.

Larger IO sizes for SMB2/3 by default
The default values ​​for “smb2 max read”, “smb2 max write” and “smb2 max trans” have been changed to 8388608 (8MiB) in order to match the default of Windows 2012R2.

SMB2 leases
The SMB2 protocol allows clients to aggressively cache files locally above and beyond the caching allowed by SMB1 and SMB2 oplocks.

Called SMB2 leases, this can greatly reduce traffic on an SMB2 connection. Samba 4.2 now implements SMB2 leases.

It can be turned on by setting the parameter “smb2 leases = yes” in the [global] section of your smb.conf. This parameter is set to off by default until the SMB2 leasing code is declared fully stable.

Improved DCERPC man in the middle detection
The DCERPC header signing has been implemented in addition to the dcerpc_sec_verification_trailer protection.

Overhauled “net idmap” command
The command line interface of the “net idmap” command has been made systematic, and subcommands for reading and writing the autorid idmap database have been added. Note that the writing commands should be used with great care. See the net(8) manual page for details.

tdb improvements
The tdb library, our core mechanism to store Samba-specific data on disk and share it between processes, has been improved to support process shared robust mutexes on Linux. These mutexes are available on Linux and Solaris and significantly reduce the overhead involved with tdb. To enable mutexes for tdb, set
dbwrap_tdb_mutexes:* = yes
in the [global] section of your smb.conf.

Tdb file space management has also been made more efficient. This will lead to smaller and less fragmented databases.

Messaging improvements
Our internal messaging subsystem, used for example for things like oplock break messages between smbds or setting a process debug level dynamically, has been rewritten to use unix domain datagram messages.

Clustering support
Samba’s file server clustering component CTDB is now integrated in the Samba tree. This avoids the confusion of compatibility of Samba and CTDB versions as existed previously.

To build the Samba file server with cluster support, use the configure command line option –with-cluster-support. This will build clustered file server against the in-tree CTDB and will also build CTDB. Building clustered samba with previous versions of CTDB is no longer supported.

Samba Registry Editor
The utility to browse the samba registry has been overhauled by our Google Summer of Code student Chris Davis. Now samba-regedit has a Midnight-Commander-like theme and UI experience. You can browse keys and edit the different value types. For a data value type a hexeditor has been implemented.

Bad Password Lockout in the AD DC
Sambas AD DC now implements bad password lockout (on a per-DC basis).

That is, incorrect password attempts are tracked, and accounts locked out if too many bad passwords are submitted. There is also a grace period of 60 minutes on the previous password when used for NTLM authentication (matching Windows 2003 SP1:

The relevant settings can be seen using ‘samba-tool domain passwordsettings show’ (the new settings being highlighted):
Password informations for domain ‘DC=samba,DC=example,DC=com’
Password complexity: on
Store plaintext passwords: off
Password history length: 24
Minimum password length: 7
Minimum password age (days): 1
Maximum password age (days): 42
* Account lockout duration (mins): 30 *
* Account lockout threshold (attempts): 0 *
* Reset account lockout after (mins): 30 *
These values ​​can be set using ‘samba-tool domain passwordsettings set’.

Correct defaults in the smb.conf manpages
The default values ​​for smb.conf parameters are now correctly specified in the smb.conf manpage, even when they refer to build-time specified paths. Provided Samba is built on a system with the right tools (xsltproc in particular) required to generate our man pages, then these will be built with the exact same embedded paths as used by the configuration parser at runtime. Additionally, the default values ​​read from the smb.conf manpage are checked by our test suite to match the values ​​seen in testparm and used by the running binaries.

Consistent behavior between samba-tool testparm and testparm
With the exception of the registry backend, which remains only available in the file server, the behavior of the smb.conf parser and the tools ‘samba-tool testparm’ and ‘testparm’ is now consistent, particularly with regard to default values. Except with regard to registry shares, it is no longer needed to use one tool on the AD DC, and another on the file server.

VFS WORM module
A VFS module for basic WORM (Write once read many) support has been added. It allows an additional layer on top of a Samba share, that provides a basic set of WORM functionality on the client side, to control the writeability of files and folders.

As the module is simply an additional layer, share access and permissions work like expected – only WORM functionality is added on top. Removing the module from the share configuration, removes this layer again. The filesystem ACLs are not affected in any way from the module and treated as usual.

The module does not provide complete WORM functions, like some archiving products do! It is not audit-proof, because the WORM function is only available on the client side, when accessing a share through SMB! If the same folder is shared by other services like NFS, the access only depends on the underlying filesystem ACLs. Equally if you access the content directly on the server.

For additional information, see

vfs_fruit, a VFS module for OS X clients
A new VFS module that provides enhanced compatibility with Apple SMB clients and interoperability with a Netatalk 3 AFP fileserver.

The module features enhanced performance with reliable named streams support, interoperability with special characters commonly used by OS X client (eg ‘*’, ‘/’), integrated file locking and Mac metadata access with Netatalk 3 and enhanced performance by implementing Apple’s SMB2 extension codenamed “AAPL”.

The modules behavior is fully configurable, please refer to the manpage vfs_fruit for further details.

smbclient archival improvements
Archive creation and extraction support in smbclient has been rewritten to use libarchive. This fixes a number of outstanding bugs in Samba’s previous custom tar implementation and also adds support for the extraction of zipped archives. smbclient archive support can be enabled or disabled at build time with corresponding –with[out]-lib archive configure parameters.

Version number 4.2.0
Release status Final
Operating systems Linux, BSD, Solaris, UNIX
Website samba
File size


License type GPL