This is exactly the advice I needed. Thanks for the reference to <http://www.kernel.org/doc/Documentation/fb/modedb.txt>.
I did a search for "kernel parameters debian video=" and got many hits, but not this one. It was probably on about page 519. On Wed, 2025-07-23 at 17:10 -0400, Felix Miata wrote: > Van Snyder composed on 2025-07-23 13:41 (UTC-0700): > > > On Wed, 2025-07-23 at 00:03 -0400, Felix Miata wrote: > > > > For troubleshooting purposes, inxi -G with no other options is > > > little short > > > of useless. With graphics issues, best to provide inxi -GSaz -- > > > vs. Bookworm's > > > inxi is broken, so should be upgraded from upstream using the -U > > > switch as > > > superuser after unblocking the -U switch in /etc/inxi.conf, or by > > > upgrading > > > the Debian inxi package to the backports version. e.g.: > > > > # inxi -GSaz --vs --za --hostname > > > Thanks for this advice. It revealed what I believe I need to know: > > What > > is the name of the interface for the display that I want to > > activate? > > > I saw a message that advised putting "video=HDMI-A-1" (which is the > > name revealed by inxi) onto the vmlinuz line using a > > GRUB_CMDLINE_LINUX*= line in /etc/default/grub. Would that make > > that > > display the only one, or simply make it "exist" along with ones > > that > > are detected to be working during boot? > > > inxi reported > > > empty: DP-1, DP-2, HDMI-A-1, HDMI-A-2, HDMI-A-3, HDMI-A-4 > > > There's only one HDMI connector, so I assume the name I ought > > (maybe) > > to put into the vmlinuz option is not DP-* or HDMI-A-[234]. > > HDMI-A-1 would be kernel name, which is the most likely name you > would need to use > with video=. With video=HDMI-A-1, whatever its continuation that > follows will > apply exclusively to that output. If you wish the same mode applied > on all > displays, leave out the output name, e.g. video=2560x1440@60. This is > all in > <http://www.kernel.org/doc/Documentation/fb/modedb.txt>.
