Using Debian Stretch. My computer starts with the screen sideways. I can set it right with xrandr -o 0 but this only works for the session. Using rc.local does not work because X session is not running then.
Can I somehow set the default screen orientation so that the login screen and following are oriented correctly across sessions?
If you have the fbcon module in your kernel (this is usually the case), then you can control screen rotation for text mode using that. Per this answer (for Ubuntu, but it's generally applicable):
First, make sure that fbcon is working:
$ echo 1 | sudo tee /sys/class/graphics/fbcon/rotate
(or rotate_all to affect all virtual framebuffers; valid values are 0 through 3, starting normally and rotating 90° clockwise for each additional number.)
If the rotation works, add or edit the GRUB_CMDLINE_LINUX (or GRUB_CMDLINE_LINUX_DEFAULT if you're paranoid) line in /etc/default/grub:
GRUB_CMDLINE_LINUX="fbcon=rotate:1"
(replace 1 with whatever value worked for you.)
Run sudo update-grub (or whatever you use to update your grub.cfg configuration).
If your computer boots using EFI, you may need to add video=efifb to GRUB_CMDLINE_LINUX.
Make a script, start it with #!/bin/bash and add the command which fixes your screen. Then add the script in crontab so it gets executed on every boot:
crontab -e @reboot path_to_script/name_of_script.bash
This will allow your fix to be automatically applied as PC boots.
