ptyfs and chroot environments

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

(I am not subscribed to this list, so please cc me in replies.)

ptyfs interacts badly with chroot environments.  Since there can be
only one ptyfs mount at any given time, a chroot environment cannot
use ptm(4) to allocate ptys, because it will return /dev/pts/N to the
userland, which does not (and cannot) exist in the chroot environment.

Consequently, for example, when I try to run xterm inside a chroot
environment on a system with a ptyfs mounted, it fails.  Testing
programs in chroot environments is invaluable to me -- it lets me make
sure that, say, a pkgsrc upgrade or a new X server works before I
clobber my main file system.  I didn't notice this in NetBSD 4 because
sysinst didn't start mounting ptyfs by default until NetBSD 5.

I can work around this by unmounting ptyfs, and that's what I'll do
for now.  Are there any other ways around this?  Is there a danger to
having multiple ptyfs mounts, or could the ptyfs code be adapted to
support this?