@Homeboy76 @Lughnasadh @V0latyle
According to https://www.getdroidtips.com/root-pixel-android-13-magisk/
They recommend fastboot boot magisk_patched.img instead of FLASH. Which one should I follow?
One live boots the image, the other flashes it.
fastboot boot <image>
tells bootloader to immediately boot the image specified without flashing it to the partition. This is called a "live boot" because the image is being loaded directly into memory, instead of being installed on the device.
fastboot flash boot <image>
tells the bootloader to flash the specified image to the boot partition.
As has been explained before, it's important to understand the context here.
is telling the command line to use the fastboot program to talk to your bootloader.
The next item is the command you're sending to the bootloader -
to tell it to "boot" the image you specify,
to flash a partition. There's other commands but that's another discussion.
Lastly is the file you're telling the bootloader to do something with, as well as any arguments that may be necessary.
It can be confusing because
fastboot flash boot
look similar, but you have to understand what is going on.
If you want to test an image, or use it to boot the device (with the express understanding that it is NOT being written to the partition) you live boot it. We can do this with Magisk patched boot images to see if they boot; since that's what is running in system RAM, the Magisk app can use that image for root access, including patching the image already in the /boot partition.
Otherwise, you can flash the image, but understand that flashing an image to a partition overwrites everything that was in that partition. This is why users of TWRP cannot flash the TWRP.img to /boot, because it overwrites ramdisk and the system kernel, so now you only have TWRP in boot, meaning the device will only boot TWRP and is unable to load system. So, instead, you'd live boot the TWRP image, use it to flash whatever modifications you might want, then use the TWRP menus to reboot the device.