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Postfix Archives: Re: 64K User Barrier on Linux

Re: 64K User Barrier on Linux

Bruno Lopes F. Cabral (brunoopenline.com.br)
Thu, 25 Nov 1999 09:17:02 -0200 (EDT)

Hi there

this is what I'm trying here, a custom system with NO users on /etc/passwd
soft quotas and all files sharing the same UID/GID

you can get this using maildrop to deliver local mail and it's support
to virtual users and soft quotas using maildrop's userdb feature. see
http://www.flounder.net/~mrsam/maildrop/ and
http://maildropl.listbot.com/cgi-bin/subscriber?Act=view_message&list_id=maildropl&msg_num=242&start_num=

(In my case I'll regenerate the userdb/ from SQL periodically --
it would be nice if postfix can accept an "user_database = [ /etc/passwd | /etc/password.db | /etc/userdb ]" and can deliver maildir++ mailboxes using
maildrop's softquotas and such directly. perhaps later ;) )

OTOH there is also the WING mail system, a GPL'd mail system that
scales well to thousands of users with no special system support needed
(it uses exim instead of postfix for mailing, though). look at it at
CPAN's nearest mirror on modules/by-authors/Malcolm_Beattie/wing-0.6.tar.gz

Cyrus-IMAP also does handle this task internally, even with LDAP support.
http://andrew2.andrew.cmu.edu/cyrus/imapd/

good luck
!3runo

> > >> I was talking with a guy today who mentioned that their server would soon
> > >> max out at 64K users. They said it was a Linux thing and were looking at
> > >> other Unix clones. The only reason I see this maxing out here is if they
> > >> were authenticating via passwd, yet I assume they would be using POP before
> > >> SMTP and an SQL database. Is there some other factor that's eluding me
> > >> here? (They're running qmail)

> > > Uids on many systems are limited to 16 bits. If each user is
> > >given a uid, you will run out at 64K-1.
> >
> > Excuse my ignorance, but when you're using pop before smtp authentication
> > via SQL database can't you bypass this by having single UID own all the
> > mailboxes and have POP daemon configured not to grant access to different
> > mailboxes w/o reauthentication? Particularly since most ISP's already have
> > such a database for their Raduis servers anyways?
>
> First of all, they may want every user to have a uid, regardless of
> where there info is. That at least means all the standard Unix "just
> works" for one. Radius servers can just as easily authenticate via Unix
> mechanisms (probably easier).

This archive was generated by hypermail 2.0b3 on Thu Nov 25 1999 - 05:19:05 CST