[Samba] winbind offline logon

[Rowland Penny]

On Wed, 10 Jan 2024 14:52:12 +0000
bd730c5053df9efb via samba <samba at lists.samba.org> wrote:

> I can confirm that on slackware too if I use rid as the backend for
> the ad domain winbind works offline and the system doesn't slow to a
> crawl for every process I try to start.

The 'problem' (if it is a problem) with using  the 'ad' backend is
that everything has to be pulled from AD, it is my understanding that
user information is only cached at login.
 
> 
> Maybe if ad backend used to work, as stated previously in the thread,
> it could be fixed since the rid backend has some drawbacks and ad
> backend has some reasons to be the preferred option but at least for
> now it is possible for me to use the rid backend until and if the ad
> backend is fixed to allow offline logon working again. FWIW I'm using
> samba 4.18.9 in slackware and 4.17.12-Debian in debian.
> 

What are the drawbacks of using the 'rid' backend that you see ?
AD, whilst it has all the rfc2307 attributes, it only really uses a
very small portion of them:

uidNumber
gidNumber
gecos
uid
loginShell
unixHomeDirectory

If I run 'getent passwd rowland' on a Unix domain member using the
'rid' idmap backend', I get this:

rowland:*:11104:10513:Rowland Penny:/home/rowland:/bin/bash

Which would seem to be:
username:??:UID:GID:?????:Home Directory:login shell

The '??' is I believe meant for the 'shadow' field.
The '?????' is the gecos field, but 'rowland' doesn't have a 'gecos'
attribute, so winbind must be filling in this field from either a
combination of the givenName and sn attributes, or the displayName
attribute, all three are in AD.

I cannot see any drawbacks there, which just leaves us with the user
home directory and login shell. If you use the 'ad' backend, then you
can set individual paths for home directories and shells, but what does
this really give you and couldn't you live without this facility ?

The only real thing that using the rfc2307 attributes gives you, is that
your users & groups will have the same IDs everywhere in Unix land.
However, do you really need this ? I thought you did, but testing
proved otherwise. 

The following presumes that no rfc2307 attributes are used:
If I have a share on a DC (yes, I know you shouldn't, but this is
theoretical) and my user 'rowland' saves a document to that share, it
will end up belonging to a numeric ID in the '3000000' range.
If 'rowland' creates another document in a share on a Unix domain
member that uses the 'rid' backend, with the DOMAIN low range starting
at '10000', the document will end up belonging to a numeric ID such as
'11104'
If you run 'ls' on both machines, the shares will be shown to belong to
'rowland', different machines, different IDs, but the same username. If
you then copy one document from one share to another, it will show as
belonging to 'rowland' on the new machine.

So I ask again, what are the drawbacks with using the 'rid' backend ?

Rowland