Bug#56264: apt-get fails on postinst when /usr partition exists

[Bear Giles <bear@coyotesong.com>]

Package: apt,
Version: 0.3.16

When upgrading a 2.1r4 system with ca. 600 packages to 2.2 (2000-02-23
snapshot), "apt-get upgrade" failed dozens of times during post-inst.
To clear "dpkg -C" (and "apt-get upgrade") I had to reload ca. 150 packages 
manually with dpkg.

Immediately prior to apt-get bombing it almost always had a line 
something like

  Dpkg::...   mount /usr -oro,umount... busy... failed

(I didn't write down the exact message, and now I can't recreate the
message since my system is fully upgraded after several hours of tedious
work.)

To say I was shocked by this message is an understatement - AFAIK
I was never asked for permission to remount /usr read-only during the
installation of apt or dpkg.  This is clearly a policy decision which
must be left to the system adminstrator -- and which is a *huge*
headache when dpkg makes assumptions about what the user wants.

To the point, "apt-get install" usually succeeded.  But "apt-get install"
left /usr "read-only", so I was forced to remount /usr read-write every 
time.  It was literally easier for me to run "apt-get upgrade" until it
bombed, then run dpkg manually (which didn't remount /usr), than to try 
to load hundred of packages individually and remount /usr because some 
idiot decided to force a policy decision on me.

N.B., I know why /usr should be mounted read-only... and I usually run
with my system set up that way.  But it should be left to the user to
make that change - the user knows if they're installing one package, or
one hundred, and anyone running dpkg should know local policy regarding
read-only partitions.  I DO NOT APPRECIATE WASTING HOURS OF TIME BECAUSE
apt/dpkg CAN'T EVEN LIVE WITH THE POLICY DECISION IT SEIZED FROM ME.

Also, modifying apt or dpkg to remount /usr as read-write is *not* a
valid solution to the "apt-get install" problem, since it potentially
violates site policy even worse than remounting /usr as read-only.

As mentioned above, this is the snapshot from 2000-01-23, and the
2.2.14 kernel.