cvs commit: src/etc/etc.amd64 ttys src/etc/etc.arm ttys src/etc/etc.i386 ttys src/etc/etc.ia64 ttys src/etc/etc.mips ttys src/etc/etc.powerpc ttys src/etc/etc.sparc64 ttys

Robert Watson rwatson at
Sun Aug 24 08:30:49 UTC 2008

On Sun, 24 Aug 2008, Ed Schouten wrote:

> * Robert Watson <rwatson at> wrote:
>> So users using slightly old versions of screen, etc, shouldn't appear in 
>> finger(1), w(1), or receive messages from biff(1), talk(1), write(1), 
>> wall(1), shutdown(8), and dump(8), all of which (I believe) rely on utmp(5) 
>> to determine who is logged in and where?  I'm sure that quite a few of 
>> these are of diminishing significance in the current world order (certainly 
>> biff is), but I'm not convinced that we should exclude users on historic 
>> tty devices from receiving advance notice of system shutdowns or dump 
>> events.
> Right now we're actually digging up the entire dynamic vs static linkage 
> discussion again. If people run a dynamically linked version of screen, 
> xterm, etc, they are not affected (except of course).

I'm not sure I see such a tight congruence: historical applications don't use 
the POSIX PTY calls, since they didn't exist or were unreliably implemented 
for many years.  Instead, applications embedded the pty allocation policy in 
the same way they embed the BPF allocation policy, which is to search a series 
of hard-coded names until they find a match.

> The current /etc/ttys already seemed like an improvement when compared to 
> the old one, where we spent 2 out of 3 entries on commonly unused PTY names. 
> What kind of ratio do you propose?

For 256 lines in /etc/ttys, you can keep people's systems working with older 
applications.  Doesn't seem like a big sacrifice -- it's not like we're 
forcing Giant to be kept on part of the kernel, etc.

Robert N M Watson
Computer Laboratory
University of Cambridge

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