IDMAP_AUTORID(8) System Administration tools IDMAP_AUTORID(8)NAMEidmap_autorid - Samba's idmap_autorid Backend for Winbind
DESCRIPTION
The idmap_autorid backend provides a way to use an algorithmic mapping
scheme to map UIDs/GIDs and SIDs that is more deterministic than
idmap_tdb and easier to configure than idmap_rid.
The module works similar to idmap_rid, but it automatically configures
the range to be used for each domain, so there is no need to specify a
specific range for each domain in the forest, the only configuration
that is needed is the range of uid/gids that shall be used for
user/group mappings and an optional size of the ranges to be used.
The mappings of which domain is mapped to which range is stored in
autorid.tdb, thus you should backup this database regularly.
Due to the algorithm being used, it is the module that is most easy to
use as it only requires a minimal configuration.
IDMAP OPTIONS
rangesize = numberofidsperdomain
Defines the number of uids/gids available per domain range. The
minimum needed value is 2000. SIDs with RIDs larger than this value
will be mapped into extension ranges depending upon number of
available ranges. If the autorid backend runs out of available
ranges, mapping requests for new domains (or new extension ranges
for domains already known) are ignored and the corresponding map is
discarded.
Example: with rangesize set to 10000, users/groups with a RID up to
10000 will be put into the first range for the domain. When
attempting to map the an object with a RID of 25000, an extension
range will be allocated that will then be used to map all RIDs from
20000-29999.
One range will be used for local users and groups and for
non-domain well-known SIDs like Everyone (S-1-1-0) or Creator Owner
(S-1-3-0). A chosen list of well-known SIDs will be preallocated on
first start to create deterministic mappings for those.
Thus the number of local users and groups that can be created is
limited by this option as well. If you plan to create a large
amount of local users or groups, you will need set this parameter
accordingly.
The default value is 100000.
read only = [ yes | no ]
Turn the module into read-only mode. No new ranges will be
allocated nor will new mappings be created in the idmap pool.
Defaults to no.
ignore builtin = [ yes | no ]
Ignore any mapping requests for the BUILTIN domain. Defaults to no.
THE MAPPING FORMULAS
The Unix ID for a RID is calculated this way:
ID = REDUCED RID + IDMAP RANGE LOW VALUE + RANGE NUMBER * RANGE SIZE
where REDUCED RID = RID % RANGE_SIZE and a DOMAIN RANGE INDEX = RID /
RANGE_SIZE is used together with the domain sid to determine the RANGE
NUMBER (stored in the database).
Correspondingly, the formula for calculating the RID for a given Unix
ID is this:
RID = (ID - LOW ID) % RANGE SIZE + DOMAIN RANGE INDEX * RANGE SIZE
Where the DOMAIN RANGE INDEX is retrieved from the database along with
the domain sid by the RANGE NUMBER = (ID - LOW ID) / RANGE SIZE .
EXAMPLES
This example shows you the minimal configuration that will work for the
principial domain and 19 trusted domains / range extensions.
[global]
security = ads
workgroup = CUSTOMER
realm = CUSTOMER.COM
idmap config * : backend = autorid
idmap config * : range = 1000000-1999999
This example shows how to configure idmap_autorid as default for all
domains with a potentially large amount of users plus a specific
configuration for a trusted domain that uses the SFU mapping scheme.
Please note that idmap ranges and sfu ranges are not allowed to
overlap.
[global]
security = ads
workgroup = CUSTOMER
realm = CUSTOMER.COM
idmap config * : backend = autorid
idmap config * : range = 1000000-19999999
idmap config * : rangesize = 1000000
idmap config TRUSTED : backend = ad
idmap config TRUSTED : range = 50000 - 99999
idmap config TRUSTED : schema_mode = sfu
AUTHOR
The original Samba software and related utilities were created by
Andrew Tridgell. Samba is now developed by the Samba Team as an Open
Source project similar to the way the Linux kernel is developed.
Samba 4.0 10/20/2013 IDMAP_AUTORID(8)
