Idmap config autorid

Introduction

The autorid back end works similar to the rid ID mapping back end, but can automatically assign IDs for different domains. This enables you to use the autorid back end:

• For the * default domain and additional domains, without the need to create ID mapping configurations for each of the additional domains.
• Only for specific domains.

For alternatives, see Identity Mapping Back Ends.

ID mapping back ends are not supported in the smb.conf file on a Samba Active Directory (AD) domain controller (DC).
For details, see Failure to Access Shares on Domain Controllers If idmap config Parameters Set in the smb.conf File.

Benefits and Drawbacks

Benefits:

• All domain users and groups whose calculated UID and GID is within the configured range are automatically available on the domain member.
• You do not need to manually assign IDs, home directories, and login shells.
• No duplicate IDs, even if multiple objects in a multi-domain environment have the same RID.

Drawbacks:

• User and group IDs are not equal across Samba domain members.
• All domain users get the same login shell and home directory assigned. However, you can use variables.
• You can not exclude individual users or groups from being available on the domain member, except the calculated UID or GID is outside of the configured range.

Configuring the autorid Back End

To configure a Samba domain member to use the autorid ID mapping back end for the * default domain:

• Edit the [global] section in your smb.conf file

If you use autorid for the default domain, adding additional ID mapping configurations for domains is optional.

• Enable the autorid ID mapping back end for the * default domain:

idmap config * : backend = autorid

• Set a range that is big enough to assign IDs for all existing and future objects. For example:

idmap config * : range = 10000-24999999

Samba ignores users and groups whose calculated IDs in this domain are not within the range. For details about how the back end calculated IDs, see the THE MAPPING FORMULAS in the idmap_autorid(8) man page.

After you set the range and Samba started using it, you can only increase the top end of the range. Any other change on the range can result in new ID assignments, and thus in loosing file ownerships.

• Optionally, set a range size. For example:

idmap config * : rangesize = 200000

Samba assigns this number of continuous IDs for each domain's object until all IDs from the range set in the idmap config * : range parameter are taken. For further details, see the rangesizeparameter description in the idmap_autorid(8) man page.

• Set a shell and home directory path that will be assigned to all mapped users. For example:

template shell = /bin/bash
template homedir = /home/%U

For details about variable substitution, see the VARIABLE SUBSTITUTIONS section in the smb.conf(5) man page.

• Optionally, add additional ID mapping configurations for domains. If no configuration for an individual domain is available, Samba calculates the ID using the autorid back end settings in the previously configured * default domain.

If you configure additional back ends for individual domain, the ranges for all ID mapping configurations must not overlap.

• Reload the Samba configuration:

# smbcontrol all reload-config

Additional Resources

• idmap_autorid(8) man page

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