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Re, Re: BSD-fileflags
From: stealth () DIONE IDS PL (stealth () DIONE IDS PL)
Date: Sun, 4 Jul 1999 16:46:15 -0400

I might add that to be able to unmount /usr, if that is indeed where
/usr/bin/login is being run from, or any other filesystem for that
matter, it needs to be totally unused.  For this reason, I think you
would be hard pressed to have /usr unmounted in a manner that would
go undetected unless you were in single luser mode.  Depending on
what else runs on the system and how packages are installed, the
same might be true for other file systems often used for installation
of binaries (/usr/local).  To give you some idea of the programs which
would need to have been stopped before unmounting /usr are as follows:

syslogd, update, cron, inetd, getty

(according to NetBSD-1.4).  That said, I do think that the claims made
by the documentation for securelevel 1 are false and should instead
mention something about changing file flags through "conventional means"
with a more complete briefing available for securelevel 2.

Right. You will run in trouble if you try to umount /usr without
'preparing' the system for it. To do this you also have to link UZip statically
b/c libc is in /usr. This also means the other programs as syslogd etc.
Some of them (getty) will die without explicitly kill them.
Althought hard, it's not impossible and on my test system i was able to remove
an immutable /usr/bin/login _without_ booting into single user (why the hell 'user'
isn't it for root? :-) mode.

Regardless whats written in the README, you have to define FORCE_OR_NOT to
MNT_FORCE (not 1) if it should be done the 'umount -f' way, sorry.


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