Messages in this thread | | | Date | Sat, 2 Aug 2008 22:08:00 -0700 | From | sukadev@us ... | Subject | Re: Per-instance devpts |
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H. Peter Anvin [hpa@zytor.com] wrote: > Since the issue of PTY namespaces came up (and was rejected) back in April, > I have thought a little bit about changing ptys to be tied directly into a > devpts instance. devpts would then be a "normal" filesystem, which can be > mounted multiple times (or not at all). pty's would then become private to > a devpts instance.
Sorry, I thought we were going with a complete device namespace - since that would address other devices as well and would avoid the following user-space issue.
I guess this issue came up in OLS recently and have been looking into this again. I have some helper patches to explore multiple mounts of devpts without namespace stuff and can send them out in a couple of days.
> > This is what it would appear would have to change, and I'd like to get > people's feeing for the user-space impact: > > 1. /dev/ptmx would have to change to a symlink, ptmx -> pts/ptmx.
IIRC, /dev/tty also needs a similar symlink.
> 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.
Sukadev
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