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Patched SAMBA+ packages are now available to address the Netlogon protocol change introduced by Microsoft’s latest updates to Windows Active Directory Domain Controllers.

Following our initial announcement, the updates from Microsoft introduce a critical change that may impact Samba installations in certain configurations. To ensure compatibility, fixed SAMBA+ packages have been released for the following branches:

• SAMBA+ 4.21
• SAMBA+ 4.22

If you are still using an older release branch, we strongly recommend migrating to 4.21 or 4.22 to receive the necessary fix.

Who needs the update?
You only need to install the patched packages if:

• Samba is configured as a member server, and
• you're using the idmap backend ad

Other Samba setups are not affected.

For full technical details, please refer to the official Samba release notes:
Samba 4.21.7 Release Notes
Samba 4.22.3 Release Notes

If you need help updating your installation or have questions about compatibility, feel free to contact us – we’re happy to support you.

Debian 13 "Trixie" has not yet been officially released, but SAMBA+ packages are already available. Starting with version 4.22, SerNet provides prebuilt SAMBA+ packages for the upcoming Debian release. Supported architectures are amd64 and arm64, in line with Debian’s decision to discontinue 32-bit variants.

By offering early access to these packages, the SAMBA+ team ensures that administrators and IT professionals can plan and test ahead. This proactive approach supports smooth transitions and secure operations in demanding environments.

Built from the official Samba source code, SAMBA+ packages offer more than just compatibility. They include extended testing, continuous security updates and the option for enterprise-grade support directly from SerNet.

All supported platforms, including the new Trixie packages, are listed in our overview. Technical setup instructions and repository details are available in the How-to Section. 

For questions, feel free to contact us at sales@remove-this.sernet.com

(Last Update: July 7)

On July 8, Microsoft will release an important security update for Active Directory Domain Controllers for Windows Server versions prior to 2025.

This update modifies the Microsoft RPC Netlogon protocol to improve security by tightening access checks for a set of RPC requests. Samba running as domain members in these environments will be impacted by this change if a specific configuration is used. See below for details on the affected configurations.

Windows Server version 2025 is already equipped with these specific security hardenings. Microsoft plans to deploy them to all supported Windows Server versions down to Windows Server 2008. 

Who is affected?
Samba installations that act as member servers in Windows AD domains will be affected if they are configured to use the 'ad' idmapping backend. Samba servers that do not use this configuration will not be affected by the change – at least according to our current knowledge and understanding – and no further action is required.

However, current versions of Samba with the affected configuration will no longer function correctly once the Microsoft update has been applied. Users will not be able to connect to the SMB service provided by Samba for any domain that uses the ‘ad’ idmapping backend.

What is SerNet doing?
The SAMBA+ team at SerNet, along with other members of the international Samba team, has been collaborating with Microsoft. Changes to Samba are currently being developed and tested to ensure full compatibility between Samba and Microsoft products. The Samba team aims to release updated packages on Monday evening (UTC+2).

Updated SAMBA+ packages, which will restore full compatibility, are planned to be made available before Microsoft's rollout.

What you should do:

• Check your configuration if you’re running Samba in a Windows AD environment.
• Watch out for new SAMBA+ package updates early next week (starting July 7th) .
• Apply the update before Microsoft’s rolls out the patch.

All SAMBA+ updates are included in active subscriptions.

If you do not yet have a subscription, visit the SAMBA+ shop (EUR) or SAMBA+ shop (USD) for access.

For any questions or individual support, feel free to contact us directly – our team is here to help.

With Samba version 4.22, support for “reflink copies” has been extended. Reflink stands for Reference Links: a feature that significantly speeds up the copying of large files by creating only references to data blocks on supporting file systems.

The feature was developed by the Samba team at SerNet GmbH in close cooperation with storage manufacturer FAST LTA, who commissioned the implementation. The aim was to fulfill an essential step so that storage systems such as FAST LTA's Silent Bricks can also support Veeam's Fast Clone feature for SMB access under Linux.

Technical background

“Reflink copies” use features of modern file systems such as Btrfs, XFS, ZFS, or ReFS to make data duplication more efficient. With SMB-based access, clients can use SMB protocol features for “reflink copies,” provided that the server and its file system support this. Previously, support in Samba was limited to the Btrfs file system.

In Samba 4.22, general support is now enabled for all file systems that support the “reflink copies” functionality – by using the generic Linux ioctl FICLONERANGE. This enables the use of backup software such as Veeam, which regularly creates complete or differential copies of large amounts of data, with file systems other than Btrfs, ZFS, and XFS. Thanks to the extension in Samba, Linux-based SMB backends – such as those provided by FAST LTA with the Silent Bricks storage system – can now also support Veeam's Fast Clone. This significantly improves performance for so-called “forever incremental” and “synthetic full” backups. The result is a reduction in storage requirements, I/O load, and backup times.

Upstream tops proprietary

The technical implementation was carried out by the Samba team at SerNet lead by Ralph Böhme, who has been working on central components of the project for many years as a member of the Samba Core Team. The code has been fully integrated upstream and is now part of the official Samba release series 4.22.

“For us, it is an important signal when manufacturers such as FAST LTA specifically focus on the further development of open source components,” says Ralph Böhme. “Such contributions not only strengthen the functionality of individual systems, but also the sustainability and openness of the overall architecture.”

Christian Rogg, lead developer at FAST LTA, is enthusiastic about the collaboration with SerNet: “It started out as just an idea. The implementation with SerNet was extremely professional, and the results are impressive. Veeam users now save up to 50% in storage capacity and backup time with Fast Clone Support with Silent Bricks.”

Joint development initiatives

As part of its development services, SerNet offers specific enhancements and customizations of Samba – especially for manufacturers, OEMs, and operators of complex infrastructures. The aim of such collaborations is to combine individual requirements with open source practice: Developments are designed transparently, implemented with technical expertise, and merged into the official Samba source code base for the benefit of Samba users worldwide

Contact us for more development opportunities with SerNet!

What is probably the world's first productive setup of Samba and Linux clients with SMB3 UNIX Extensions is now up and running at Frankfurt University of Applied Sciences (UAS). Björn Jacke from the SerNet Samba team recently worked with colleagues from the university's IT department to equip the Samba server and connected Linux clients with this new feature for academic purposes.  

Frankfurt UAS had consciously decided not to use dual protocols SMB and NFS. Instead, it now relies on uniform integration with SMB3: Samba's rights and sharing management offers much greater flexibility and easier administration. Without the Unix Extensions, students using Linux workstations were previously restricted in that symlinks or Unix commands such as chmod did not behave as they would on a typical POSIX/Linux system. The operations could not be mapped directly via the SMB protocol. Jacke: “With the new SMB3 UNIX Extensions, Linux clients now work perfectly with SMB mounts from Samba servers, enabling optimal integration without compromise. This makes studying at Frankfurt University even more enjoyable for students.”

Samba 4.22 with SMB3 Unix Extensions

The SMB3 UNIX Extensions feature is available since Samba version 4.22, which was released in April 2025. The topic also dominated this year's sambaXP and can be reviewed in several recordings published on the SAMBA+ YouTube channel.

SerNet has already incorporated some additional features into the current SAMBA+ packages, which will only be part of Samba from version 4.23 onwards in fall 2025.

SerNet: Worldwide partner for Samba projects

Support – remote or directly onsite – is part of the core business of SerNet's Samba team. The team supports companies and organizations in setting up, maintaining, and optimizing Samba infrastructures. The project implementation in Frankfurt shows how practical know-how and technological development come together at the customer's site.

How can we assist you with your Samba environment?

SerNet offers professional assistance with all questions relating to Samba, SMB, and Active Directory – from planning and implementation to ongoing support and development projects. Find out more about our services or contact us directly.