Configuring a Windows SMB share

How to set up a general purpose Server Message Block (SMB) share.

  18 minute read

SMB (also known as CIFS) is the native file sharing system in Windows. SMB shares can be connected to any major operating systems including Windows, MacOS, and Linux. SMB can be used in TrueNAS to share files with one user or device, or many.

SMB shares allow a wide range of permissions and security settings, and can support advanced permissions (ACLs) on Windows and other systems, as well as Windows Alternate Streams and Extended Metadata. SMB is suitable for the management and administration of large or small pools of data.

TrueNAS uses Samba to provide SMB services. There are multiple versions of the SMB protocol. An SMB client will typically negotiate the highest supported SMB protocol during SMB session negotiation. Industry-wide the usage of the SMB1 protocol (sometimes referred to as NT1) is in the process of being deprecated. This deprecation is largely due to security reasons, and for this reason most SMB clients support the SMB2/3 protocol even if it is not the default protocol used by the particular SMB client.

Please see the separate advisory for more information about the SMB1 protocol.

You will need a dataset with the data to share stored within it before creating an SMB share.

Requirements for a new SMB share

  1. Create a dataset. Typically, a new dataset should be created when creating a new SMB share. It is recommended to use the SMB Share Type preset for the ZFS dataset. This will set the ZFS dataset’s aclmode property to “restricted”, case sensitivity to “insensitive”, and apply a default ACL on the newly created dataset. The default ACL is restrictive and will only grant access to the dataset owner and group. Further modification of this default ACL may be required depending on intended usage of the share.

  2. Create a user. Although it is possible to grant anonymous or guest access to SMB shares, the support for this is in the process of being deprecated by major vendors of SMB clients. This is in part due to the fact that signing and encryption are not possible for guest sessions. It is therefore recommended to create one or more user accounts for SMB access. By default all new local users are members of a builtin SMB group “builtin users”. This group may be used as a simple control point to grant access to all local users on the server. Additional groups may be created to simplify assigning permissions to large numbers of users. User accounts that are built-in or do not have the ‘smb’ flag set may not be used for SMB access.

  3. Fine-tune dataset ACL as needed. In most circumstances for home users a reasonable step at this point is to add a new ACL entry to the ACL of the dataset created in (1) above that grants “FULL_CONTROL” to the group “builtin_users” with the flags set to “INHERIT”. See the Permissions article for more details about configuring dataset permissions.

Creating the SMB Share

To create a Windows SMB share, go to Sharing > Windows Shares (SMB) and click ADD.



The **Path** and **Name** of the SMB share define the absolute minimum amount of information required to create a new SMB share. The *Path* is the directory tree on the local filesystem that will be exported over the SMB protocol, and the *Name* is the name of the SMB share, which forms a part of the "full share pathname" when SMB clients perform an SMB tree connect. Because of the way that the *Name* is used in the SMB protocol, it must be less than or equal to 80 characters in length, and must not contain any invalid characters as specified in Microsoft documentation MS-FSCC section 2.1.6. If a *Name* is not supplied, then the last component of the *Path* will be used as the share name.

You can set a share Purpose to apply and lock pre-defined Advanced Options for the share. To retain full control over all the share Advanced Options, choose No presets. The following table shows the preset options for the different Purposes and if those options are locked. An [x] indicates the option is enabled, [ ] means the option is disabled, and [text] indicates a specific value:

Default share parametersMulti-user time machineMulti-protocol (AFP/SMB) sharesMulti-protocol (NFSv3/SMB) sharesPrivate SMB Datasets and SharesFiles become readonly of SMB after 5 minutes
[x] Enable ACL (locked)[x] Enable ACL (unlocked)[x] Enable ACL (locked)[ ] Enable ACL (locked)[ ] Enable ACL (unlocked)[ ] Enable ACL (unlocked)
[ ] Export Read Only (locked)[ ] Export Read Only (unlocked)[ ] Export Read Only (unlocked)[ ] Export Read Only (unlocked)[ ] Export Read Only (unlocked)[ ] Export Read Only (unlocked)
[x] Browsable to Network Clients (locked)[x] Browsable to Network Clients (unlocked)[x] Browsable to Network Clients (unlocked)[x] Browsable to Network Clients (unlocked)[x] Browsable to Network Clients (unlocked)[x] Browsable to Network Clients (unlocked)
[ ] Allow Guest Access (unlocked)[ ] Allow Guest Access (unlocked)[ ] Allow Guest Access (unlocked)[ ] Allow Guest Access (unlocked)[ ] Allow Guest Access (unlocked)[ ] Allow Guest Access (unlocked)
[ ] Access Based Share Enumeration (locked)[ ] Access Based Share Enumeration (unlocked)[ ] Access Based Share Enumeration (unlocked)[ ] Access Based Share Enumeration (unlocked)[ ] Access Based Share Enumeration (unlocked)[ ] Access Based Share Enumeration (unlocked)
[ ] Hosts Allow (locked)[ ] Hosts Allow (unlocked)[ ] Hosts Allow (unlocked)[ ] Hosts Allow (unlocked)[ ] Hosts Allow (unlocked)[ ] Hosts Allow (unlocked)
[ ] Hosts Deny (locked)[ ] Hosts Deny (unlocked)[ ] Hosts Deny (unlocked)[ ] Hosts Deny (unlocked)[ ] Hosts Deny (unlocked)[ ] Hosts Deny (unlocked)
[ ] Use as Home Share (locked)[ ] Use as Home Share (unlocked)[ ] Use as Home Share (unlocked)[ ] Use as Home Share (unlocked)[ ] Use as Home Share (unlocked)[ ] Use as Home Share (unlocked)
[ ] Time Machine (locked)[ ] Time Machine (unlocked)[ ] Time Machine (unlocked)[ ] Time Machine (unlocked)[ ] Time Machine (unlocked)[ ] Time Machine (unlocked)
[x] Enable Shadow Copies (locked)[x] Enable Shadow Copies (unlocked)[x] Enable Shadow Copies (unlocked)[x] Enable Shadow Copies (unlocked)[x] Enable Shadow Copies (unlocked)[x] Enable Shadow Copies (unlocked)
[ ] Export Recycle Bin (locked)[ ] Export Recycle Bin (unlocked)[ ] Export Recycle Bin (unlocked)[ ] Export Recycle Bin (unlocked)[ ] Export Recycle Bin (unlocked)[ ] Export Recycle Bin (unlocked)
[ ] Use Apple-style Character Encoding (locked)[ ] Use Apple-style Character Encoding (unlocked)[x] Use Apple-style Character Encoding (locked)[x] Use Apple-style Character Encoding (unlocked)[x] Use Apple-style Character Encoding (unlocked)[x] Use Apple-style Character Encoding (unlocked)
[x] Enable Alternate Data Streams (locked)[x] Enable Alternate Data Streams (unlocked)[x] Enable Alternate Data Streams (locked)[ ] Enable Alternate Data Streams (locked)[ ] Enable Alternate Data Streams (unlocked)[ ] Enable Alternate Data Streams (unlocked)
[x] Enable SMB2/3 Durable Handles (locked)[x] Enable SMB2/3 Durable Handles (unlocked)[ ] Enable SMB2/3 Durable Handles (locked)[ ] Enable SMB2/3 Durable Handles (locked)[ ] Enable SMB2/3 Durable Handles (unlocked)[ ] Enable SMB2/3 Durable Handles (unlocked)
[ ] Enable FSRVP (locked)[ ] Enable FSRVP (unlocked)[ ] Enable FSRVP (locked)[ ] Enable FSRVP (unlocked)[ ] Enable FSRVP (unlocked)[ ] Enable FSRVP (unlocked)
[ ] Path Suffix (locked)[%U] Path Suffix (locked)[%U] Path Suffix (unlocked)[%U] Path Suffix (unlocked)[%U] Path Suffix (locked)[ ] Path Suffix (locked)
[ ] Auxiliary Parameters (unlocked)[ ] Auxiliary Parameters (unlocked)[ ] Auxiliary Parameters (unlocked)[ ] Auxiliary Parameters (unlocked)[ ] Auxiliary Parameters (unlocked)[ ] Auxiliary Parameters (unlocked)

An optional Description can be specified to help explain the purpose of the share.

Enabled allows this path to be shared when the SMB service is activated. Unsetting Enabled disables the share without deleting the configuration.

Advanced Options

To fine-tune the share configuration, click ADVANCED OPTIONS.



Options are divided into Access and Other Options groups. Access options control various settings for allowing systems or users to access or modify the shared data.

SettingValueDescription
Enable ACLcheckboxSet to add Access Control List (ACL) support to the share. Unsetting disables ACL support and will delete any existing ACL for the share.
Export Read OnlycheckboxProhibits writes to the share. Unset to allow writes to the share.
Browsable to Network ClientscheckboxDetermine whether this share name is included when browsing shares. Home shares are only visible to the owner regardless of this setting.
Allow Guest AccesscheckboxPrivileges are the same as the guest account. Guest access is disabled by default in Windows 10 version 1709 and Windows Server version 1903. Additional client-side configuration is required to provide guest access to these clients.

MacOS clients: Attempting to connect as a user that does not exist in FreeNAS does not automatically connect as the guest account. The Connect As: Guest option must be specifically chosen in MacOS to log in as the guest account. See the Apple documentation for more details.
Access Based Share EnumerationcheckboxSetting this restricts share visibility to users with read or write access to the share. See the smb.conf manual page.
Hosts AllowstringEnter a list of allowed hostnames or IP addresses. Separate entries by pressing Enter. A more detailed description with examples can be found here.
Hosts DenystringEnter a list of denied hostnames or IP addresses. Separate entries by pressing Enter.

The Hosts Allow and Hosts Deny fields work together to produce different situations:

  • If neither Hosts Allow or Hosts Deny contains an entry, then SMB share access is allowed for any host.
  • If there is a Hosts Allow list but no Hosts Deny list, then only allow hosts on the Hosts Allow list.
  • If there is a Hosts Deny list but no Hosts Allow list, then allow all hosts that are not on the Hosts Deny list.
  • If there is both a Hosts Allow and Hosts Deny list, then allow all hosts that are on the Hosts Allow list. If there is a host not on the Hosts Allow and not on the Hosts Deny list, then allow it.

The Other Options have settings for improving Apple software compatibility, ZFS snapshot features, and other advanced features.

SettingValueDescription
Use as Home SharecheckboxAllows the share to host user home directories. Each user is given a personal home directory when connecting to the share which is not accessible by other users. This allows for a personal, dynamic share. Only one share can be used as the home share. See the configuring Home Share article for detailed instructions.
Time MachinecheckboxEnables Apple Time Machine backups on this share.
Enable Shadow CopiescheckboxExport ZFS snapshots as Shadow Copies for Microsoft Volume Shadow Copy Service (VSS) clients.
Export Recycle BincheckboxFiles that are deleted from the same dataset are moved to the Recycle Bin and do not take any additional space. Deleting files over NFS will remove the files permanently. When the files are in a different dataset or a child dataset, they are copied to the dataset where the Recycle Bin is located. To prevent excessive space usage, files larger than 20 MiB are deleted rather than moved. Adjust the Auxiliary Parameter crossrename:sizelimit= setting to allow larger files. For example, crossrename:sizelimit=50 allows moves of files up to 50 MiB in size. This means files can be permanently deleted or moved from the recycle bin. This is not a replacement for ZFS snapshots.
Use Apple-style Character EncodingcheckboxBy default, Samba uses a hashing algorithm for NTFS illegal characters. Enabling this option converts NTFS illegal characters in the same manner as MacOS SMB clients.
Enable Alternate Data StreamscheckboxAllows multiple NTFS data streams. Disabling this option causes MacOS to write streams to files on the filesystem.
Enable SMB2/3 Durable HandlescheckboxAllow using open file handles that can withstand short disconnections. Support for POSIX byte-range locks in Samba is also disabled. This option is not recommended when configuring multi-protocol or local access to files.
Enable FSRVPcheckboxEnable support for the File Server Remote VSS Protocol (FSVRP). This protocol allows Remote Procedure Call (RPC) clients to manage snapshots for a specific SMB share. The share path must be a dataset mountpoint. Snapshots have the prefix fss- followed by a snapshot creation timestamp. A snapshot must have this prefix for an RPC user to delete it.
Path SuffixstringAppends a suffix to the share connection path. This is used to provide unique shares on a per-user, per-computer, or per-IP address basis. Suffixes can contain a macro. See the smb.conf manual page for a list of supported macros. The connectpath must be preset before a client connects.
Auxiliary ParametersstringAdditional smb.conf settings.

Clicking Submit creates the share and adds it to the Sharing > Windows Shares (SMB) list. You can also choose to enable the SMB service at this time.

Share Management

After the SMB share is created, additional management options are available by going to Sharing > Windows Shares (SMB) and clicking   for a share entry:

  • Edit: Opens the share creation screen to reconfigure the share or disable it.
  • Edit Share ACL: Opens a screen to configure an Access Control List (ACL) for the share. This is separate from filesystem permissions, and applies at the level of the entire SMB share. Permissions defined here are not interpreted by clients of other filesharing protocols or other SMB shares that export the same share Path. The default is open. This ACL is used to determine the browse list if Access Based Share Enumeration is enabled.
  • Edit Filesystem ACL: Opens a screen to configure an Access Control List (ACL) for the path defined in the share Path.
  • Delete: Remove the share configuration from TrueNAS. Data that was being shared is unaffected.

Configure Share ACL

Open the share options ()  and click Edit Share ACL to see options for the Share ACL.



The Share Name is shown, but cannot be changed. ACL Entries are listed as a block of settings. To add a new entry, click ADD.

SettingValueDescription
SIDstringWho this ACL entry (ACE) applies to, shown as a Windows Security Identifier. Either a SID or a Domain and Name is required for the ACL.
DomainstringDomain for the user Name. Required when a SID is not entered. Local users have the SMB server NetBIOS name: truenas\\smbusers.
Permissiondrop downPredefined permission combinations:
Read: Read access and Execute permission on the object (RX).
Change: Read access, Execute permission, Write access, and Delete object (RXWD).
Full: Read access, Execute permission, Write access, Delete object, change Permissions, and take Ownership (RXWDPO).

For more details, see smbacls(1).
NamestringWho this ACL entry applies to, shown as a user name. Requires adding the user Domain.
Typedrop downHow permissions are applied to the share. Allowed denies all permissions by default except those that are manually defined. Denied allows all permissions by default except those that are manually defined.

Clicking SAVE stores the share ACL and applies it to the share immediately.

Configure Filesystem ACL

Open the share options ()  and click Edit Filesystem ACL to see options for the dataset ACL.



This ACL is used to define the user accounts or groups that own or have specific permissions to the dataset that is being shared. The options in this screen are detailed in the Permissions article. This section will outline how to choose a preset ACL and add an ACL entry (ACE) for a specific TrueNAS user account.

The User and Group values show which accounts “own”, or have full permissions to, the dataset. If you want to change these settings, be sure to set the Apply option before saving any changes.

There are some standard ACLs that can be applied to the dataset by clicking SELECT AN ACL PRESET and choosing an preconfigured ACL to apply. This will overwrite any current ACL entries.

To define permissions for a specific user account or group, click ADD ACL ITEM. Open the Who drop down, select User or Group, and choose the specific User or Group in the new drop down that appears. Continue to define how the settings are applied to the account then choose which permissions to apply to that account. For example, to only allow the tmoore user permission to view dataset contents but not make changes, set the ACL Type to Allow and Permissions to Read.

For more information on Managing ACLs, read the Dataset Management documentation.

SMB Service

Connecting to an SMB share does not work when the related system service is not activated. To turn the SMB service on, go to Services and click the toggle for SMB. If you want the service to activate whenever TrueNAS boots, set Start Automatically.

The SMB service is configured by clicking . Unless a specific setting is needed or configuring for a specific network environment, it is recommended to use the default settings for the SMB service.



SettingValueDescription
NetBIOS NamestringAutomatically populated with the original hostname of the system. This name is limited to 15 characters and cannot be the Workgroup name.
NetBIOS AliasstringEnter any aliases, separated by spaces. Each alias can be up to 15 characters long.
WorkgroupstringMust match the Windows workgroup name. When this is unconfigured and Active Directory or LDAP are active, TrueNAS will detect and set the correct workgroup from these services.
DescriptionstringThis allows entering any notes or descriptive details about the service configuration.
Enable SMB1 supportcheckboxAllow legacy SMB1 clients to connect to the server. Note that SMB1 is being deprecated and it is advised to upgrade clients to operating system versions that support modern versions of the SMB protocol.
NTLMv1 AuthcheckboxWhen set, smbd attempts to authenticate users with the insecure and vulnerable NTLMv1 encryption. This setting allows backward compatibility with older versions of Windows, but is not recommended and should not be used on untrusted networks.

Advanced Options

Clicking ADVANCED OPTIONS adds a new section of Other Options for fine-tuning the service.

SettingValueDescription
UNIX Charsetdrop downCharacter set used internally. UTF-8 is standard for most systems as it supports all characters in all languages.
Log Leveldrop downRecord SMB service messages up to the specified log level. By default, error and warning level messages are logged. It is not recommended to use a log level above MINIMUM for production servers.
Use Syslog OnlycheckboxSet to log authentication failures in /var/log/messages instead of the default /var/log/samba4/log.smbd.
Local MastercheckboxSet to determine if the system participates in a browser election. Unset when the network contains an AD or LDAP server, or when Vista or Windows 7 machines are present.
Enable Apple SMB2/3 Protocol ExtensionscheckboxThese protocol extensions can be used by macOS to improve the performance and behavioral characteristics of SMB shares. This is required for Time Machine support.
Administrators Groupdrop downMembers of this group are local administrators and automatically have privileges to take ownership of any file in an SMB share, reset permissions, and administer the SMB server through the Computer Management MMC snap-in.
Guest Accountdrop downAccount to be used for guest access. Default is nobody. The chosen account is required to have permissions to the shared pool or dataset. To adjust permissions, edit the dataset Access Control List (ACL), add a new entry for the chosen guest account, and configure the permissions in that entry. If the selected Guest Account is deleted the field resets to nobody.
File MaskintegerOverrides default file creation mask of 0666 which creates files with read and write access for everybody.
Directory MaskintegerOverrides default directory creation mask of 0777 which grants directory read, write and execute access for everybody.
Bind IP Addressesdrop downStatic IP addresses which SMB listens on for connections. Leaving all unselected defaults to listening on all active interfaces.
Auxiliary ParametersstringStores additional smb.conf. Auxiliary parameters may be used to override the default SMB server configuration, but such changes may adversely affect SMB server stability or behavior.

Some users have experienced issues in the Windows 10 v2004 release where network shares can’t be accessed. The problem appears to come from a bug in gpedit.msc, the Local Group Policy Editor. Unfortunately, setting the “Allow insecure guest logon” flag value to “Enabled” in Computer Configuration > Administrative Templates > Network > Lanman Workstation appears to have no effect on the configuration. To work around the issue, you will need to edit the registry. Use Regedit and go to HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters. The DWORD AllowInsecureGuestAuth will be set to the incorrect value 0x00000000. Changing this value to 0x00000001 (Hexadecimal 1) allows adjusting the settings in gpedit.msc. This can be applied to a fleet of Windows machines with a Group Policy Update.


Last modified January 20, 2021: fixed typo (f6c130cb)