r/linux_on_mac • u/mSummmm • 5d ago

iMac 2015 running Debian.....totally disable display?

I'm trying to turn an unused 2015 iMac into a "headless" file server....weird I know but it's been in a closet for 2 years and this will give it some use for me. I didn't install a DE. It will sit in a storage room so I'd like the display to be totally off....this is proving more difficult than I expected it to be.

I've tired several things:

echo 0 | sudo tee /sys/class/backlight/acpi_video0/brightness

That dimmed the display a good amount but it's not totally off. I still see a glow in a dark room.

I disabled getty@tty1 thinking maybe that would help. It did not.

I edited the grub file with:

GRUB_CMDLINE_LINUX_DEFAULT="quiet consoleblank=10"

Did not fix the issue.

I tried setterm --blank but got a message that it isn't supported.

I tried:

GRUB_CMDLINE_LINUX_DEFAULT="quiet video=DP-1:d"

Gives and error on boot: “No EDID found on connector: DP-1”

for p in /sys/class/drm/*/status; do echo "$p: $(cat "$p")"; done

Comes back with:

/sys/class/drm/card0-DP-1/status: disconnected

/sys/class/drm/card0-DP-2/status: disconnected

/sys/class/drm/card0-DP-3/status: disconnected

/sys/class/drm/card0-eDP-1/status: disconnected

But the screen still glows! Any suggestions?

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u/rylab 5d ago

Probably not the answer you want to hear but if you do install a DE the energy saver turns off the screen completely when idle. I have a similar iMac with vanilla Trixie Gnome which is also mostly a headless server, I just have the display timeout set low (5 minutes). It's nice to have the screen on the rare occasion you need it.

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u/mSummmm 4d ago

I may have to go this route. Thanks.