Server Message Block (SMB)

  5 minute read

Server Message Block shares, also known as Common Internet File System (CIFS) shares, are accessible by Windows, macOS, Linux, and BSD computers. Access is slower than an NFS share due to the single-threaded design of Samba. SMB provides more configuration options than NFS and is a good choice on a network for Windows or Mac systems. However, it is a poor choice if the CPU on the TrueNAS system is limited. If it is maxed out, upgrade the CPU or consider a different type of share.

TrueNAS uses Samba to share pools using Microsoft’s SMB protocol. SMB is built into the Windows and macOS operating systems and most Linux and BSD systems pre-install the Samba client in order to provide support for SMB. If the distro did not, install the Samba client using the distro software repository.

The SMB protocol supports many different types of configuration scenarios, ranging from the simple to complex. The complexity of the scenario depends upon the types and versions of the client operating systems that will connect to the share, whether the network has a Windows server, and whether Active Directory is being used. Depending on the authentication requirements, it might be necessary to create or import users and groups.

Samba supports server-side copy of files on the same share with clients from Windows 8 and higher. Copying between two different shares is not server-side. Windows 7 clients support server-side copying with Robocopy.

SMB Tips and Tricks shows helpful hints for configuring and managing SMB networking.

These videos help clarify setting up permissions on SMB shares:


Another helpful reference is Methods For Fine-Tuning Samba Permissions.

Samba disables NTLMv1 authentication by default for security. Standard configurations of Windows XP and some configurations of later clients like Windows 7 will not be able to connect with NTLMv1 disabled. Security guidance for NTLMv1 and LM network authentication has information about the security implications and ways to enable NTLMv2 on those clients. If changing the client configuration is not possible, NTLMv1 authentication can be enabled by selecting the NTLMv1 auth option in the SMB service configuration screen

To view all active SMB connections and users, enter smbstatus in the TrueNAS Shell.

Most configuration scenarios require each user to have their own user account and to authenticate before accessing the share. This allows the administrator to control access to data, provide appropriate permissions to that data, and to determine who accesses and modifies stored data. A Windows domain controller is not needed for authenticated SMB shares, which means that additional licensing costs are not required. However, because there is no domain controller to provide authentication for the network, each user account must be created on the TrueNAS system. This type of configuration scenario is often used in home and small networks as it does not scale well if many user accounts are needed.

Shadow Copies, also known as the Volume Shadow Copy Service (VSS) or Previous Versions, is a Microsoft service for creating volume snapshots. Shadow copies can be used to restore previous versions of files from within Windows Explorer. Shadow Copy support is built into Vista and Windows 7. Windows XP or 2000 users need to install the Shadow Copy client.

When a periodic snapshot task is created on a ZFS pool that is configured as a SMB share in TrueNAS, it is automatically configured to support shadow copies.

Before using shadow copies with TrueNAS, be aware of the following caveats:

  • If the Windows system is not fully patched to the latest service pack, Shadow Copies may not work. If no previous versions of files to restore are visible, use Windows Update to ensure the system is fully up-to-date.

  • Shadow copy support only works for ZFS pools or datasets. This means that the SMB share must be configured on a pool or dataset, not on a directory.

  • Datasets are filesystems and shadow copies cannot traverse filesystems. To see the shadow copies in the child datasets, create separate shares for them.

  • Shadow copies will not work with a manual snapshot. Creating a periodic snapshot task for the pool or dataset being shared by SMB or a recursive task for a parent dataset is recommended.

  • The periodic snapshot task should be created and at least one snapshot should exist before creating the SMB share. If the SMB share was created first, be sure to restart the SMB service.

  • Appropriate permissions must be configured on the pool or dataset being shared by SMB.

  • Users cannot delete shadow copies on the Windows system due to the way Samba works. Instead, the administrator can remove snapshots from the TrueNAS web interface. The only way to disable shadow copies completely is to remove the periodic snapshot task and delete all snapshots associated with the SMB share.

macOS includes the Time Machine feature which performs automatic backups. TrueNAS supports Time Machine backups for both SMB and AFP shares.

Configuring a quota for each Time Machine share helps prevent backups from using all available space on the TrueNAS system. Time Machine waits two minutes before creating a full backup. It then creates ongoing hourly, daily, weekly, and monthly backups. The oldest backups are deleted when a Time Machine share fills up, so make sure that the quota size is large enough to hold the desired number of backups. Note that a default installation of macOS is over 20 GiB.

Configure a global quota using the instructions in Set up Time Machine for multiple machines with OSX Server-Style Quotas or create individual share quotas.

See vfs_fruit(8) and the Apple documentation for detailed Time Machine configuration instructions.


Last modified August 31, 2020: Update SMB-references.md (b96306e4)