[RFC][PATCH 7/8]: Auto-create ptmx node when mounting devpts

sukadev at us.ibm.com sukadev at us.ibm.com
Thu Aug 21 11:11:34 PDT 2008

H. Peter Anvin [hpa at zytor.com] wrote:
> sukadev at us.ibm.com wrote:
>> I had the new ptmx node only in 'multi-mount' mode initially. But if users
>> want the multi-mount semantics, /dev/ptmx must be a symlink. If its a 
>> symlink,
>> we break in the single-mount case (which does not have the ptmx node and
>> we don't support mknod in pts).
> True, but changing that is still a configuration change (adding newns to 
> the fstab); it's not that much more work to change whatever else needs to 
> change.

Hmm, so, single and multi-mount don't coexist ? i.e some are multi-mounts
while others are single-mounts.

The way I looked at is that even if a distro has not yet updated the
startup script (fstab), we could use the multi-mount. Maybe a container
startup script could change /dev/ptmx to symlink and both types of
mounts can work simultaneously.

Would that be unnecessary ?

> I personally don't expect a whole lot of back-and-forth; I suspect people 
> will switch from the legacy model to the newns model mostly as part of a 
> distro upgrade.
>>>> I'm open to being convinced and the
>>>> other problems with that code are more pressing.
>> Yes, I will look at the latest in linux-next and the ->driver_data
>> approach.
>> But just to confirm, we do want try and keep single-mount semantics.
> Certainly for several years at least.


> 	-hpa

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