I manage servers and prefer to use VGA as graphics quality is unimportant and VGA is ubiquitous on crash carts. I'd prefer to have a single video cable on the carts, and I can think of no more common connector.

Occasionally I find a server with no VGA or DVI output, just DisplayPort, or perhaps DisplayPort + HDMI.

I have a couple DisplayPort-to-VGA adapters. But they seem to only work if the computer is rebooted. That's no good. Half the time I connect a monitor up to a server it's because something has gone wrong, and I need to investigate the current state of the system. Having to reboot erases that state and some evidence of the problem.

I think that I could leave these adapters in the servers, one per and that would let me walk up with a vga monitor and plug in. But that's impractical as well to have a bunch of dongles hanging out everywhere.

Is there a technical reason a fresh reboot is required to get vga output through a DisplayPort-to-VGA adapter?

Operating Systems tend to be linux distros. I'm wondering if the "thing" that the TTY's attach to simply does not exist until the DisplayPort-to-VGA adapter is inserted. And the TTYs start at boot time, not dynamically. So that would tell me I need to write a udev script or something to detect insertion of displayport adapter and spawn a tty on it. Though that would probably fall short of displaying printk's and such, much like using a usb-to-vga "adapter".

But I didn't think these little DP-to-VGA adapters had a frame buffer for instance, like the usb ones do.

My ideal solution would be some sort of kernel parameter to set in grub that would pre-initialize the DP port to serve as a VGA output. I tried this one to no avail: https://superuser.com/a/873826/75139

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    This probably comes down to the specifications of the server itself and/or simply due to the fact VGA isn’t digital. I speak from experience as an Administrator myself. It could also be due to the adapter you are using. You might be able to get around a full reboot my identifying the kernel service responsible. Linux is more forgiving than other OSs
    – Ramhound
    Jan 7, 2021 at 8:15
  • VGA isn't hot-swappable. DisplayPort is only hot swappable if it is supported by all hardware in the path, which is rare enough to call it not hot-swappable in most cases.
    – Tetsujin
    Jan 7, 2021 at 8:32
  • What differences do you see in dmesg between boots with the adapter attached, and boots without it? Jan 7, 2021 at 9:43
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    @Tetsujin All hot swappable things are only hot swappable if it is supported by all hardware in the path. Since when is VGA not hot swappable? Maybe you're referring to VGA DP outputs which would make more sense, because people have been hot swapping VGA connectors for decades. at user1686 gah! I'm ashamed I didn't think of that myself. I'll grab a dmesg diff next time. Jan 8, 2021 at 9:09
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    superuser.com/questions/112309/is-vga-port-hot-pluggable Users say it is, VESA says it isn't.
    – Tetsujin
    Jan 8, 2021 at 9:16


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