Map Samba4 Users to Unix UID

Check Users UID

Check the users UID by examing the appropirate passwd file, or with the id command

[user@thesystem ~]$ id dorkus
uid=2013(dorkus) gid=1005(dorkus) groups=1005(dorkus)
[user@thesystem ~]$

Create a samba4 user (if the user doesn't exist already).

root@thesystem:~ # samba-tool user add dorkus
New Password: 
Retype Password: 
User 'dorkus' created successfully
root@thesystem:~ #

Use wbinfo to excract some information from the winbind daemon. To inspect the allocated user ID and SID of a user, use the following command:

root@nas-1:~ # wbinfo --name-to-sid dorkus
S-1-5-21-1002881701-2601196197-2352697156-3105 SID_USER (1)
root@nas-1:~ # wbinfo --sid-to-uid S-1-5-21-1002881701-2601196197-2352697156-3105
3000018
root@nas-1:~ #

Change the UID Mapping

If you want to change this mapping, then use ldbedit on the .../samba/private/idmap.ldb, as shown:

First locate the file, the following is from a FreeBSD system with samba4 installed out of the ports collection:

root@thesystem:~ # find /var | grep idmap.ldb                                         /var/db/samba4/private/idmap.ldb
root@thesystem:~ #

Edit the idmap database with the ldb editor referencing the SID from the user your changing. ldb is the database engine used in Samba4 and is described as a LDAP-like embedded database. This command will open up a record in your system's editor.

root@thesystem:~ # ldbedit -e vi -H /var/db/samba4/private/idmap.ldb objectsid=S-1-5-21-1002881701-2601196197-2352697156-3105

The raw record is displayed below. The xidNumber field represents the UID of the user.

# editing 1 records
# record 1
dn: CN=S-1-5-21-1002881701-2601196197-2352697156-3105
cn: S-1-5-21-1002881701-2601196197-2352697156-3105
objectClass: sidMap
objectSid: S-1-5-21-1002881701-2601196197-2352697156-3105
type: ID_TYPE_BOTH
xidNumber: 3000018
distinguishedName: CN=S-1-5-21-1002881701-2601196197-2352697156-3105

Change the xidNumber to the users UID, and save the file.

# editing 1 records
# record 1
dn: CN=S-1-5-21-1002881701-2601196197-2352697156-3105
cn: S-1-5-21-1002881701-2601196197-2352697156-3105
objectClass: sidMap
objectSid: S-1-5-21-1002881701-2601196197-2352697156-3105
type: ID_TYPE_BOTH
xidNumber: 2013   
distinguishedName: CN=S-1-5-21-1002881701-2601196197-2352697156-3105

Test

Check your work to make sure the edit took

root@thesystem:~ # wbinfo --sid-to-uid S-1-5-21-1002881701-2601196197-2352697156-3105 2013
root@thesystem:~ #

You should be able to consistenly access files from a samba share that is also a NFS export or a local fileystem on a UNIX-like OS without having to constantly adjust owners or use world readable and writable file persmissions.

Map Samba4 Users to thier UNIX UID

Topics

Check Users UID

Change the UID Mapping

Test