etcboot.conf

/etc/boot.conf

The /etc/boot.conf file allows you to permanently reconfigure the system's booting process. Entries in this file are parsed before you get the boot prompt, so you have the opportunity to override anything you enter in this file. Commands here are parsed and processed automatically.

You can tell your OpenBSD system to boot a different kernel every time giving the command here. If /etc/boot.conf contains the following, your system will automatically boot using the kernel file /bsd.CUSTOM:

 boot /bsd.CUSTOM 

You can change the boot prompt timeout by setting it here as well. For example, if a five-second delay is just too long and you want barely enough time to hit the spacebar and start typing before the system boots, you might set your timeout to two seconds.

 set timeout 2 

By far, however, the most popular use of /etc/boot.conf is to configure a serial console.