Date: Wed, 13 Dec 2006 11:56:09 -0700 From: Eric Brunson <brunson@brunson.com> To: freebsd-questions@freebsd.org Subject: Re: Increasing ptys/ttys beyond 128 Message-ID: <45804CC9.7090807@brunson.com> In-Reply-To: <20061213183051.GA79921@owl.midgard.homeip.net> References: <45803B96.5090402@brunson.com> <20061213183051.GA79921@owl.midgard.homeip.net>
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Erik Trulsson wrote: > On Wed, Dec 13, 2006 at 10:42:46AM -0700, Eric Brunson wrote: > >> I've done some searching on the web, but everything I've come across is >> either out of date and says to recompile the kernel, or else says that >> after 5.1 the devfs does it automatically. I don't think that's the case. >> >> I'm running 6.1 and I need more than the [pt]ty[p-sP-S] devices that >> will auto-clone in devfs. >> >> I've tried adding lines like the following to /etc/default/devfs.rules: >> >> add path 'ptyt*' unhide >> add path 'ttyt*' unhide >> >> But that doesn't do the trick. The syntax "unhide" implies to me that >> the [p-sP-S] nodes exist but but are hidden by the hide_all ruleset. >> >> What do I have to do to allow the creation of more ptys? >> > > I don't think you can have more than 256 pty devices in 6.1 > > The code in the kernel that handles ptys only allow for pty[pqrsPQRS][0-9a-v] > (and the corresponding tty[pqrsPQRS][0-9a-v] of course.) This gives you a > total of 8*32 = 256 pty devices. (Not 128 as the subjectline implies.) > Actually, that is incredibly helpful. We're having problems with expect, but when expect searches for a free pty, it only searches [0-9a-f], which only gives us 128 ptys. There's another problem with this search resulting in failures after 64 pty allocations which I was trying to avoid patching in expect, but if I can get 256 processes out of it, I'll patch away. Man, 5 days of searching the web and you set me straight in 48 minutes... I should have started here first. :-) Thanks a *ton*! > (I don't think you could have more than 256 ptys back in 4.x either, but > back then the default setup only gave you 32 ptys, and all the instructions > I have seen for increasing that number only told how to let you use all 256 > possible devices, but not more than that.) > > > To get more ptys than 256 you will have to start hacking the kernel. (There > does seem to be an alternate naming system for ptys available in 7-CURRENT > but it has not been back-ported to 6.x. See the pty(4) manpage from > -CURRENT for details on how it works.
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