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From: romain@pyrnj.uucp (Romain Kang)
Newsgroups: comp.unix.wizards
Subject: Re: NGROUP limit set at 8
Message-ID: <689@pyrnj.uucp>
Date: Tue, 27-Oct-87 12:09:37 EST
Article-I.D.: pyrnj.689
Posted: Tue Oct 27 12:09:37 1987
Date-Received: Thu, 29-Oct-87 23:15:20 EST
References: <9096@mimsy.UUCP>
Reply-To: romain@pyrnj.UUCP (Romain Kang)
Organization: Pyramid Technology Corp, Woodbridge, NJ
Lines: 39
Keywords: NGROUP

In article <9096@mimsy.UUCP> sjr@mimsy.UUCP (Stephen J. Roznowski) writes:
| it seems that I need to rebuild the
| whole system to enlarge NGROUP (located in /usr/include/sys/param.h),
| because the C library uses param.h.
|
| Is there an easier solution?

Under vanllia 4.2 BSD, I got a workable system by recompiling
	/usr/src/lib/libc/gen/initgroups.c
		replace initgroups.o in /lib/libc.a, /usr/lib/libc_p.a
		initgroup dependents:
			/usr/src/bin/{login.c,su.c}
			/usr/src/ucb/groups.c
	/usr/src/bin/{ps.c,adb/}
	/usr/src/ucb/{{w,gcore}.c,dbx/}
	/usr/src/etc/{pstat,analyze}.c
(as well as the kernel, of course.)

Under some NFS'd kernels, you might not need to recompile all of
these, since the group array was moved out of the user structure.

If you don't really need to be in all those groups simultaneously,
you could simply re-implement the "newgrp" command using setgid()
calls.

| Is there a reason why the number of groups is limited to 8? (other
| that the fact that most people are in less that 8 groups...)

Last I looked, group permission validation was done by a linear scan
of the group array.  This occurs every time someone needs to open a
file, etc.  One could take a performance hit by raising NGROUPS
willy-nilly.

| A related question, how would you make this change on a binary only
| distribution?

I wouldn't try it.  Youi'd probably have to hack binaries without
symbol tables.  Most people I know don't have that sort of time to
kill.