Possible to get Samba3 to use Samba4 server idmap info

Michael Adam obnox at samba.org
Tue Aug 31 08:54:11 MDT 2010

Trever L. Adams wrote:
>  On 08/30/2010 04:05 PM, Michael Adam wrote:
> >
> > Trever,
> >
> > While currently there is indeed no such idmap backend in S3,
> > it could be certainly implemented.
> >
> > But I would like to know, why it is important for you to have
> > the same unix ids on the s4 server and on the s3 clients.
> > Generally, the connection between the client (s3) and the s4
> > server is simply windows protocols. The unix ids are additional
> > info put into play by the respective samba instances. Unless
> > you want to do something like copy or share files wit other means
> > than samba/CIFS, then it is not important to have the unix ids
> > identical on the various servers.
> >
> > So idmap_hash or idmap_rid or even idmap_tdb should be fine.
> >
> > Or maybe I am not getting your point.
> >
> > Cheers - Michael
> Michael,
> The unix uids/gids are being used by other things. Also, some times when
> moving large groups of files between servers, I find it easier to do
> rsync to save all the permissions, etc. It is nice to know that for now
> I can get around that, or at least it sounds that way from what you are
> saying.


When you are accessing / copying data between the servers with
other means than samba, you might get problems: once you start
using your idmap rid/hash/whatever setup, the unix ids thus
created start appearing in your file system as owners or in acls.
At that point you can't easily switch the idmap configuration on
the file server any more. That is you can, but it will break
ownership and permissions on disk. So you need to be really
careful once an idmap config goes productive.

If you are using rsync, do not use it with the "--numeric-ids"
switch but let it use local nsswitch name->unixid resolution.

If you want to change the id mapping in the future, be prepared
to run some scripting over your files to adapt ownership.

Cheers - Michael

> However, I really would love to see a S4 compatible idmap in S3 as it is
> far easier to use S3 for now on the clients.
> Trever
> -- 
> "My spelling is Wobbly. It's good spelling but it Wobbles, and the
> letters get in the wrong places." -- A. A. Milne (1882-1958)

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