FreeBSD 4.x EoL

[Robert Watson]

On Thu, 19 Oct 2006, Paul Allen wrote:

>> While possibly not advisable in the long term, I ran a 4.x postfix and 
>> cyrus server install on 6.x using compat4 for about six months without 
>> problems. The place where it gets tricky is updating the 4.x binaries, 
>> which requires a 4.x chroot, since I was running a native 6.x userland for 
>> everything else. I've now gotten over that, but it worked quite well and 
>> was extremely useful that I could avoid doing the upgrade all at once -- 
>> upgrade the OS first, let it settle, then upgrade the applications.  The 
>> only issue I ran into was actually that the location of the Cyrus sasl unix 
>> domain socket had moved, and once I tracked that down, all was well (so not 
>> a FreeBSD nit, an application nit).
>
> Let me toss a bit of caution from experience regarding this:
>
> I too ran such 6.x system.  It had a jailed FreeBSD 4.x userland (restored 
> and modified from the original FreeBSD 4.x backups). Almost everything 
> worked properly--but there were some strange vm related inconsistencies 
> (exposed by a program rolling its own gc implementation and using mprotect 
> and SEGV).
>
> Obviously this was an unusual case but it's unfortuantely proof that some 
> things escape having the necessary compat lines in your kernel conf.
>
> Still I counted myself lucky.

When you recompiled the application for 6.x, did the problem go away?  I guess 
I wouldn't entirely preclude an application bug, a 4.x library bug, or a 6.x 
compat/non-compat bug being responsible.  Since 6.x is a fairly major upgrade, 
there are significant changes in VM (which might well affect, for example, 
memory layout), etc, so it could well be that it triggered a bug in the GC.

Robert N M Watson
Computer Laboratory
University of Cambridge