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………………………………………………………………………………………. options DDB makeoptions DEBUG=-g ………………………………………………………………………………………. The DDB option installs the DDB kernel debugger. (This isn’t strictly necessary, but it can be helpful and it doesn’t take up that much room.) The makeoptions you set here tell the system to build a debugging kernel. Post-Panic Behavior When configuring your system, you’ll need to decide how you want the system to behave after a panic. Do you want the computer to reboot automatically, or do you want it to stay at the panic screen until you manually trigger a reboot? If the system is at a remote location, you’ll almost certainly want the computer to reboot automatically, but if you’re at the console debugging kernel changes, you might want it to wait for you to tell it to reboot. To reboot automatically, include the kernel option DDB_UNATTENDED: ………………………………………………………………………………………. options DDB_UNATTENDED ………………………………………………………………………………………. If you don’t include this option, the system will wait for you to tell it to reboot. kernel.debug Once you have the kernel configured the way you want, do the usual dance (described in Chapter 4) to configure and install it. Once you’ve installed your new kernel, you’ll find a file in the kernel compile directory called kernel.debug. This is your kernel with symbols; save it somewhere. The next time you upgrade your system or customize the kernel, this debugging kernel will be overwritten by a new debugging kernel. If you’ve built a kernel just for testing, you want to be sure that you have your known-to-be-good debugging kernel available. One of the frequent causes of a failed debugging process is losing the debugging kernel and trying to debug a crashed kernel with a different kernel.debug. This won’t work. I generally copy kernel.debug to /var/crash/kernel.debug.date, so I can tell when a particular debug kernel was built. This lets me date-match the current kernel to a debugging kernel, and also tells me when a kernel.debug is old enough that I can delete it. With any luck, you’ll never need these debugging kernels, though personally, I’ve found my luck to be unreliable. Debugging kernels take little disk space and provide quick answers when trouble hits, so I strongly suggest using them. 455

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