[Samba] Corrupted idmap...

[Alex Crow]

Yes, this does not make sense.

If I have member file servers, and I want to be in control of which
groups can access what, surely winbind needs to be able to get a GID
from AD?

It may be different in our case as we migrated from classic Samba, but
every non-builtin group we have has a GID assigned and it works
perfectly. Indeed, if I create a new group without assigning a Unix GID,
it is not even visible on the member file servers, so IMHO the advice
you've been given is not correct. Your non-builtin groups that you use
for file access controls must have a GID number if you're using rfc idmap.

I understand that idmap configuration is not usable on a DC.

Cheers

Alex


On 19/01/17 13:32, Ryan Ashley via samba wrote:
> OK, so since it appears our only recourse is to build a new domain from
> scratch, how can we prevent this from happening again? We have several
> Gentoo workstations, a bunch of Windows 7 workstations, and a few NAS
> devices which run Linux of some flavor. How do we use NIS attributes
> without killing our domain? The Samba guide even has instructions for
> using ADUC to set the UID/GID for users and groups. You stated I should
> only set a GID for "Domain Users", but what about other AD security
> groups we create? This is a tad confusing since I thought NIS was needed
> for our Linux systems and the NAS devices.
>
> Lead IT/IS Specialist
> Reach Technology FP, Inc
>
> On 01/17/2017 10:57 AM, Rowland Penny via samba wrote:
>> On Tue, 17 Jan 2017 10:04:23 -0500
>> Ryan Ashley via samba <samba at lists.samba.org> wrote:
>>
>> Firstly , 'gencache_notrans.tdb' is a cache file and is recreated when
>> Samba is restarted.
>>
>>> Rowland, I was just reading over another thread on this list about the
>>> inability to access group policy from client machines. The user did
>>> not have the symlinks setup (I do) but one thing you mentioned was
>>> using the NIS attributes to set UID/GID numbers for the domain. You
>>> said we should not do this for certain users and groups, but there is
>>> no mention of this in the guides to setting up an AD DC, so I have
>>> always done it. We do this to make our Linux-based NAS devices work.
>> The only only windows group that needs a gidNumber attribute is Domain
>> Users and then only when you use the windbind 'ad' backend on a domain
>> member. the other windows groups don't need a gidNumber, in fact, as
>> Domain Admins needs to own directories in sysvol, you definitely
>> shouldn't give this group a gidNumber.
>> If you have to set up Samba this way because of your NAS, I would look
>> closely at your NAS ;-)
>>  
>>> Furthermore, you recommended the user use the idmap lines to ensure
>>> consistent UID/GID numbers across devices, yet you suggested I turn
>>> the exact same lines off in my config. Why is this? I understand our
>>> situations are different, but when should we set winbind to use the AD
>>> backend and set UID/GID numbers? How do do this so Linux-base file
>>> services can be accessed by users and come out the same?
>> You are mixing up idmap on a DC and a Unix domain member. On a DC,
>> idmapping is done in idmap.ldb, users & groups are allocated an
>> xidNumber in the '3000000' range, the number allocated is on the next
>> number available basis, apart from 'Administrator', 'Domain Users' and
>> 'nobody' which get '0', '100' and '65534'.
>>
>> On a Unix domain member, the two main ways of setting up idmapping is
>> with the winbind 'rid' and 'ad' backends. The 'rid' backends calculates
>> an ID from the windows RID, so you don't have to add anything to AD.
>> This means that whilst, by using the 'rid' backend, you will get the
>> same ID on every Unix domain member, it will still be different from
>> the ID on a DC (and the ID will probably be different on other DCs).
>>
>> The only way to get the same ID everywhere is to use the 'ad' backend,
>> If you give a user a uidNumber and run 'net cache flush', this will be
>> used instead of the xidNumber without modifying smb.conf in any way.
>> On a Unix domain member it is different, you need to add something
>> like this:
>>
>>     idmap config *:backend = tdb
>>     idmap config *:range = 2000-9999
>>     ## map ids from the domain  the ranges may not overlap !
>>     idmap config SAMDOM : backend = ad
>>     idmap config SAMDOM : schema_mode = rfc2307
>>     idmap config SAMDOM : range = 10000-999999
>>
>> Now provided that the uidNumber attributes you have added are between
>> 10000 and 999999 AND you have given Domain users a gidNumber in the
>> same range, getent will display info for your users.
>>
>> Now somebody (and I know who) recommended adding those lines to the
>> smb.conf, but they do nothing on a DC, well they didn't until 4.5.0
>> came out and then they started causing errors, so bottom line, don't add
>> them to a Samba AD DC smb.conf
>>
>> Rowland
>>
>>


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