sudo pacman -S linux-headers
Arch package search is a great friend.
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To be fair @Kresimir, I missed that in the readme for Optimus-Switch.
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I guess I donât understand the difference between headers and kernel. I was following the wikiâŚwhich was originally made for Manjaro.
I gave you the exact command to put in to install Linux-Headers. I even admitted that I missed that in my initial read through.
Linux-headers is a way of adding functionality to the kernel. It is seperate from the kernel. Manjaro uses their own kernels and has their own way of managing packages for it. Because I am so used to doing things âthe non-Manjaro wayâ, I missed that in the instructions.
You probably already have linux-headers installed, so skip this. If unsure, check with
pacman -Q | grep headers
(this is how you should always check if you have something installed or not, regardless whether it is from the repos or the AUR)
Thank you.
Thanks for that. Very helpful. I installed them before I saw your message. It seemed to install with no problems. Does the below mean I have two different sets of headers or are they used for different things?
pacman -Q | grep headers
linux-api-headers 5.7-1
linux-headers 5.8.5.arch1-1
If you are unsure what a package does, a good starting point is to look it up on:
Alternatively, you can:
pacman -Qi linux-headers
pacman -Qi linux-api-headers
To display info about those packages. In this case, linux-api-headers and linux-headers are entirely different things, you should keep both.
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Thank you. I am saving all these in a file so I have them for later.
I just went through the installation, but realized that I skipped the line
sudo modprobe acpi_call
When I run it now, I get
sudo modprobe acpi_call
modprobe: FATAL: Module acpi_call not found in directory /lib/modules/5.8.4-arch1-1
Do I need to uninstall and start over?
No, just make sure you have acpi_call-dkms installed. Remember how to check?
pacman -Q | grep acpi
If you donât see it, install it:
sudo pacman -S acpi_call-dkms
And then run
sudo modprobe acpi_call
Yes, I saved that in a file so I can remember. Thank you. (BTW, what happens if you install a package that you already have? Can it cause issues? I thought it just reinstalls it or lets you know it is already installed.)
After running it, it wasnât installed, so I installed it. But still got the same error
sudo modprobe acpi_call
modprobe: FATAL: Module acpi_call not found in directory /lib/modules/5.8.4-arch1-1
Packages (1) acpi_call-dkms-1.1.0-287
Total Download Size: 0.01 MiB
Total Installed Size: 0.03 MiB
:: Proceed with installation? [Y/n] y
:: Retrieving packages...
acpi_call-dkms-1.1.0-... 11.7 KiB 510 KiB/s 00:00 [-----------------------------] 100%
(1/1) checking keys in keyring [-----------------------------] 100%
(1/1) checking package integrity [-----------------------------] 100%
(1/1) loading package files [-----------------------------] 100%
(1/1) checking for file conflicts [-----------------------------] 100%
:: Processing package changes...
(1/1) installing acpi_call-dkms [-----------------------------] 100%
:: Running post-transaction hooks...
(1/2) Arming ConditionNeedsUpdate...
(2/2) Install DKMS modules
==> dkms install --no-depmod -m acpi_call -v 1.1.0 -k 5.8.5-arch1-1
==> depmod 5.8.5-arch1-1
Did you update your kernel without rebooting? It seems you are running 5.8.4, but have 5.8.5 installed.
You should always reboot after updating your kernel. Especially before installing graphics drivers. 
Now I worry that if you reboot, youâll get a black screenâŚ
Yes. I havenât rebooted.
Yes, this is a real concern for me as well as it happened many times when I first installed Manjaro.
If I do get a black screen I can boot using systemd.unit=rescue.target to get to a terminal. What will I need to do from there to make sure I can get the computer back?
If you canât boot, youâll probably have to uninstall Nvidia drivers and start all over 
Well, just YOLO it⌠
okay. Hopefully I can manage that. So
sudo pacman -R nvidia-installer-dkms
sudo pacman -S nvidia-installer-dkms
No, just reboot. Donât do anything else.
I mean if boot fails. Should I try that?
No, you already have nvidia-installer-dkms installed. Youâll have to remove the drivers (not the installer) and run the installer again. Hopefully you have another computer or a phone you can use to read this forum.
Okay, here goes nothing. lol