[BRLTTY] Console open error on recent Arch Linux

[Dave Mielke]

[quoted lines by Aura Kelloniemi on 2025/10/01 at 11:13 +0300]

>BRLTTY is unable to access console on my system, because /dev/tty0 is
>accessible only by the root user, its mode is 0600 and ownership root:tty.

Okay, thanks. Maybe this is somehow non-standard. On my system - and apparently on most others - there's write permission (though not read) to the group.

>I'm running kernel 6.16.9-arch1-1 and there are no udev rules which affect
>permissions of my /dev/tty0, so it seems these permissions are the kernel
>default.

Maybe. I'm not at that kernel release yet or maybe Arch does something new now. We'd need other users to let us know for sure.

>Would this work?
>
>1) Start BRLTTY as root.
>2) unshare. Detach from the common mounts namespace.
>3) Mount private tmpfs. Only BRLTTY process has access to this file system.
>4) Create necessary device nodes in this private file system. Not all device
>nodes need to be created, only those for which cannot be accessed from /dev
>directly.
>5) Switch user to brltty and drop all privileges.
>6) Once BRLTTY exits or is killed, the mount namespace becomes empty and the
>tmpfs is cleaned up.

Yes, that's a good idea although I think we need to make one modification. It's possible that brltty's drivers, tables, and configuration files are mounted so we'd need to keep all those mounts and just create a private mount for that one directory.

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