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Re: [Samba] samba 4 ad member - idmap = ad for machine accounts


Drawbacks for RID, yes, multiple, but maybe it does not apply for you.

Read the Advantages and Disadvantages
My reason for NOT using RID on FILESERVER setups.
Only one : File ownership of domain users and groups are lost, when the local ID mapping database corrupts.

I think this line is an unfortunate "copy & paste" from a TDB backend disadvantage listing. Indeed IDMAP RID is based on RID like its name states, so there is no mapping database, only a local cache.

IMHO the only item that really matters in the "disadvantages" section is : "All users on the domain member get the same login shell and home directory base path assigned", and the others points are not that relevant.

With Ad, i just remove and reinstall samba again and im up and running, no worries about incorrect ACL's.

But again, this is a choice.
An good example for RID.
A proxy server member set, does get RID setup.
( if you dont login with ssh as an AD user and use the shared homedir over nfs )

The only two cases where I keep a rfc2307 mapping during a migration are technical/historical constraints (eg. uidnumber are used all over the place in UNIX contexts, like NFS mounts, user profiles, mail servers user mappings, old solaris workstations, etc.), or it is too much of a hassle to reset too many ACLs on too many file servers. In other cases, during classic upgrade I just switch old rfc2307 mapping to RID.

Handling rfc2307 mapping is not (yet) fully transparent, its command line tooling is not fool proof, RSAT rfc2307 on win7 isn't really ergonomic, and the "unix attributes" tab disappeared on win10...

msSFU30MaxUidNumber attribute has no pooling system like RID, so there is nothing preventing you from having two users with identical uid on a large domain... I had a talk with Andrew Bartlett about having a pooling system for uidnumber/gidnumber like the RID one, that would indeed make rfc2307 a first class citizen.

If you have scripts/automation for user creation from HR department database, above rfc2307 issues are void, but such setup is unfortunately not yet so common.





-----Oorspronkelijk bericht-----
Van: samba [mailto:samba-bounces@xxxxxxxxxxxxxxx] Namens
Kacper Wirski via samba
Verzonden: maandag 18 september 2017 16:20
Aan: "samba@xxxxxxxxxxxxxxx"
Onderwerp: Re: [Samba] samba 4 ad member - idmap = ad for
machine accounts

	Thank everyone for input,

	It seems that using RID is the way to go. I just tried
a few things:


	- made group, assigned unix GID

	- added test PC to this group and set this group as
"primary group"

	- added manually to test PC account "uidnumber"

	on server with samba

	getent passwd MYDOMAIN\\testpc$

	returns nicely testpc$ with UID and GID numbers as set
in AD, but authentication still doesn't work, i.e. no test
writes to share


	- added GID to default "DOMAIN COMPUTERS"

	rest steps are the same, except didn't need to add PC
to this group

	getent passwd gives same, OK result, still unable to


	I'm out of ideas I guess I have to stick with RID,
since it "just works"


	So my question is if using RID is reliable across
different samba
installations, that is:

	if I make file-server1, file-server2 and use same idmap
range for MYDOMAIN,
will I get identical UIDs? Since they're calculated from
"rid" portion of
the "sid", they should be, right?


	Also I know the drawbacks of using SYSTEM -> machine
accounts for writes.
Share with said backups is itself backed up to completely
different machine
with completely different methods, so it's safe enough (or should be).




	Dnia 2017-09-18 15:53 Rowland Penny via samba napisa??(a):

	On Mon, 18 Sep 2017 14:55:04 +0200 Denis Cardon
		Hi Rowland,
				File server config looks
exactly like this, except more shares, all with
same simple config. I know that "use defualt domain" isn't
necessery, but
it's not the issue for me right now.
			'SYSTEM' is a Windows group and is
meaningless to Unix, it should be
mapped to a Unix ID only on a Samba AD DC and there it is an
'xidNumber' not
a 'uidNumber or 'gidNumber'. Running 'wbinfo -S S-1-5-18'
(the SID for
'SYSTEM' is S-1-5-8-18) on a UNIX domain member, returns:
failed to call
wbcSidToUid: WBC_ERR_DOMAIN_NOT_FOUND Could not convert sid
S-1-5-18 to uid
However "wbinfo -Y S-1-5-18" returns: 2005 (note your ID may
be different)
As I said, you could use the kerberos machine account
instead, but are these
scripts being run on the fileserver, Samba DC or windows
machines ? if the
later, then you shouldn't need a Unix IDs.
				2)'m using some machine
autostart scripts, for various tasks, which work
again as SYSTEM, so if they have to get anything from network
share, they
need to have read/write permission. What I'm doing is, for
example, as
autostart run a batch script, that would check
\\fileserver\public\test-file.txt if %COMPTURNAME% exists in
this file. if
not - run some robocopy script, then >> %COMPUTERNAME% to the
end of the
file. or even something simple like this: "if exist
\\server\share\%computername%.txt (exit) else robocopy
some-files echo . >
\\server\share\%computername%.txt exit"
			That looks like a Windows script (not
that I am an expert on Windows
script languages) so I presume that it is run a Windows
machine and 'SYSTEM'
should be available on it via its name or SID.
				3) Some windows applications
that I use also run as SYSTEM account and
they have built-in backup utilities, and if I want to backup
straight to
network share - again - machine account needs direct write
access to share.
			Hmm, I think I am beginning to
understand your problem, you are confusing
'SYSTEM' with the computers account in AD. 'SYSTEM' does not
exist in AD, so
you cannot give it a uidNumber or gidNumber attribute. I
think you need to
find another way to do what you are doing now.
		Kacper way of doing things is completly correct
(at least from
authentication point of view). SYSTEM account on Windows uses
the machine
account for authentication. So for example, using psexec [1],
you can try
(on an elevated command prompt): psexec -s -i cmd.exe Check
that you are
local system whoami then you connect to a share (sysvol is a
good choice
here since "domain computers" has access) net use F:
Then on your DC you can check which account has been used for
the connexion:
smbstatus You'll see that SYSTEM account uses the Kerberos
machine account
for authentication.
	Thanks Yes that works, but it shows that you don't need
the computers to
have uidNumber attributes, which is what I was trying to get
across to the
OP. Rowland -- To unsubscribe from this list go to the
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Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
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