Re: Non-privileged user can only connect to /dev/pts/X once?!

[Marcin Cieslak]

On Thu, 4 Jun 2020, Joe Yeung wrote:

> Thanks for your response.
> I am a bit busy today and wasn’t able collect the errno from the failed open() 
> call.

I think screen prints that out too - in my case screen was saying Permission 
denied as well.

> My system is running Yocto with screen 4.8 but this issue is also observable on 
> Ubuntu.
>
> In your case where the pts jumps from 3 to 4, how did you find out it had gone 
> to 4 in the first place?
> One of my challenges is to find out what pts qemu uses when I spun up the VM. 
> Fortunately it is displayed on the command line. If it is to jump around like 
> your set up, that would be painful because at any instance of time, you 
> wouldn’t know which pts to use.

I just did ls /dev/pts and observed changes there (FreeBSD has its own devfs 
probably similar to
the Linux one). It was interesting to see 0 1 2 3 listed and then 0 1 2 4 and 
then back to 0 1 2 3
and so forth...

Intestesting note in the pty(4) manpage:

BUGS
     Unlike previous implementations, the master and slave device nodes are
     destroyed when the PTY becomes unused.  A call to stat(2) on a
     nonexistent master device will already cause a new master device node to
     be created.  The master device can only be destroyed by opening and
     closing it.

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