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Is there a way of emulating the Linux virtual console inside X? I. e. an environment where /dev/tty for all practical purposes (ioctl_console(2)) acts exactly as the Linux console would but that runs as an X client and can be fired up at will and allows screenshots?

I want to avoid having to resort to QEMU if possible.

(Note that a terminal emulator will no do as it does not support the required ioctl()s.)

Background: I’m programming against the virtual console and need a more efficient (and possibly automatable) approach to testing.

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  • What exactly do which terminal emulators not support?
    – Hauke Laging
    Nov 23, 2021 at 20:59
  • @HaukeLaging: “What exactly do which terminal emulators not support?” — the ioctls I gave. E. g. int main(){char c; assert(ioctl (0, KDGETLED, &c) == 0); }.
    – Philipp Gesang
    Nov 23, 2021 at 21:18

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No.

While you could emulate any ioctl()s you want with cuse, that's not enough to implement a terminal like /dev/tty1 is -- whose interface also includes job control (i.e. correctly forwarding signals like SIGHUP or SIGTTIN to processes), not just some extra ioctl()s.

Notice that you can make a snapshot of real linux "console" has via the /dev/vcsX and /dev/vcsaX (text mode) or /dev/fbX (framebuffer), so reimplementing it sounds pretty pointless -- just like targetting the linux console in particular, which is not even guaranteed to exist even on Linux systems (and in fact it does not exists on 99.9% of Linux systems ;-))

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  • I hadn’t heard about CUSE, thanks for the pointer. Very intriguing, but it’d also mean that I have to implement the kernel side of things. Unlikely to happen today. ;)
    – Philipp Gesang
    Nov 23, 2021 at 22:34
  • “Notice that you can make a snapshot of real linux "console"” — oh yeah, definitely. Still to actually run test code on that console I’d have to deal with getty. Which would be a pain to automate and probably requires privileged access. Booting a VM is probably the simpler approach.
    – Philipp Gesang
    Nov 23, 2021 at 22:34
  • “And in fact it does not exists on 99.9% of Linux systems” — granted, though it exists on 100 % of systems I care for. ;)
    – Philipp Gesang
    Nov 23, 2021 at 22:35

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