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Absolute OpenBSD, 2nd Edition by Michael W. Lucas

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Boot-Time Kernel Configuration

The config kernel editor is great when you know what you’re doing, but many of us aren’t that lucky or educated. When I’m trying to figure out how to fix a problem, I’ll frequently make a change, reboot to test the change, and see if things work.

OpenBSD lets you edit the kernel at boot time. You can try one boot with a kernel change, see if it works, and write your changes to the kernel. At the boot loader prompt, run boot -c.

boot > boot -c

You’ll get a couple lines of boot output, and then the kernel editor prompt.

ukc>

This works just like the config kernel configuration editor. Make any changes you want here, exactly as you would with config. When you quit the editor, the kernel should boot with the changes ...

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