alan at lxorguk.ukuu.org.uk
Sun Aug 3 05:04:39 PDT 2008
> > 1. /dev/ptmx would have to change to a symlink, ptmx -> pts/ptmx.
> IIRC, /dev/tty also needs a similar symlink.
Making them symlinks is asking for trouble because some code does go
around using stat and the like and tools like MAKEDEV have definite ideas.
For /dev/tty the definition is precisely that it is your controlling
tty. No reference to namespace and a task whose controlling tty is in a
different namespace should still open the controlling tty not some
parallel in another universe when you open /dev/tty.
If you want to make sure the controlling tty is in the right namespace
that can be done in userspace when transferring control into a namespace.
In many cases I doubt that is even what is wanted.
> > 2. Permissions on /dev/ptmx would not be persistent, and would have to
> > be set via devpts mount options (unless they're 0666 root.tty, which
> > would presumably be the default.)
> > 3. The /proc/sys/kernel/pty limit would be global; a per-filesystem
> > limit could be added on top or instead (presumably via a filesystem
> > mount options.)
> > I worry #1 would have substantial user-space impact, but I don't see a way
> > around it, since there would be no obvious way to associate /dev/ptmx with
> > a filesystem.
/dev/tty and /dev/ptmx already primarily operate by identifying a device
and switching the work to that. Actually putting a bit of namespace logic
in the driver code so the actual files stay as expected (device nodes
etc) seems a *lot* simpler than trying to do symlink hacks.
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