[Bug 195734] New: vt(4) / Newcons causes unbootable system in the absence of a graphics card

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195734

            Bug ID: 195734
           Summary: vt(4) / Newcons causes unbootable system in the
                    absence of a graphics card
           Product: Base System
           Version: 10.1-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: zurvan.akarana at gmail.com

CPU: AMD FX-4100
Motherboard: ASUS Sabertooth 990FX R2.0

I have a home server with above specs which I run headless. It does not have
integrated graphics and I insert a regular PCI-E graphics card only when the
system becomes inaccessible over SSH.

This arrangement has worked fine from 8.0-RELEASE up to and including
10.0-RELEASE.

When I upgraded to 10.1-RELEASE and rebooted the system failed to reach a stage
where I could access it over SSH. Inserting a graphics card, however, and
viewing the boot process showed no errors.

The system boots from BIOS so by default 'sc' console driver is loaded.

After struggling with various combinations of loader.conf settings I came to
the following conclusions:

1. If the system is without a graphics card and boots from BIOS, i.e. loads
'sc' by default, the only way to get past bootloader and successfully boot is
to force 'vt' driver with 'kern.vty=vt' and force text mode with
'hw.vga.textmode=1' in loader.conf.

2. If the system has a graphics card and 'kern.vty=vt' is forced but
'hw.vga.textmode=1' is not forced the system boots only when a display is
plugged into the graphics card. Otherwise, it waits indefinitely at bootloader
stage.

3. If the system has a graphics card, boots from BIOS, is allowed to load the
default 'sc' driver it boots fine without a display plugged into the graphics
card.

4. If the system has no graphics card, boots from BIOS, and is allowed to
proceed with defaults it will not get past bootloader.

For my situation I used conclusion (1), added those two lines to loader.conf.
Now I can run the system headless and without a graphics card as I was able to
prior to 10.1-RELEASE.

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