[BRLTTY] BRLTTY, systemd and unprivileged user

[Dave Mielke]

[quoted lines by Aura Kelloniemi on 2020/08/23 at 11:48 +0300]

>BRLTTY fails to open /dev/tty1 (Permission denied) 

This is a perfect example of why user-testing of prerelease code is so very
helpful. I hadn't noticed this very serious problem because, on my system, X
starts on tty1 so I log in using tty2. In your case (and that of many others),
tty1 is being used to log in because X isn't consuming it.

It turns out that the console login stuff removes group permissions from the
active tty (the one a user is logged in using). So, yes, in my case, group
permissions are removed from tty2 while I'm logged in. And, of course, group
permissions would be being removed from tty1 while you're logged in.

So why was tty1 so critical to brltty? It needs to use a tty to do certain
things, the most important of which is to determine which tty is active at any
given moment. It was using tty1 for this because that's the only one guaranteed
to exist. With group permissions removed from tty1 while you're logged in,
brltty, when running without privileges, was unable to open it and the Linux
screen driver was unable to start.

I think this problem has now been fixed. I'd appreciate it if you could verify
that it's no longer a problem for you. Of course, be sure that you're logged in
via tty1 when verifying.

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