KfWiki: Compiling kernel

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Compiling kernel

cd /usr/src/sys/i386/conf
cp GENERIC MYKERNEL
# Edit MYKERNEL with a text editor. e.g adding ipfw support, add the followings:
options         QUOTA
options         IPFIREWALL
options         IPFIREWALL_VERBOSE
options         IPFIREWALL_VERBOSE_LIMIT=1000
options         IPFIREWALL_FORWARD
# SMP
options SMP
options APIC_IO

# on freebsd 7, already in GENERIC config
options         SMP
device          apic

Build and install

cd /usr/src
make buildkernel KERNCONF=MYKERNEL
make installkernel KERNCONF=MYKERNEL

The new kernel will be copied to the /boot/kernel directory as /boot/kernel/kernel and the old kernel will be moved to /boot/kernel.old/kernel. Reboot to use the new kernel. If your new kernel does not boot, choose the kernel you want to boot from at the FreeBSD boot loader. You can access this when the system boot menu appears. Select the “Escape to a loader prompt” option, number six. At the prompt, type unload kernel and then type boot /boot/kernel.old/kernel.

Rolling back to previous kernel

at the boot prompt, do these

ok unload
ok boot kernel.old

Then if your box is not in secure mode, you can do these to rename /kernel.old to /kernel:

# check securelevel

sysctl kern.securelevel

# remove secure flag

chflags noschg /kernel

# rename the kernel and modules

mv kernel.old kernel

mv modules.old modules

KfWiki : FreeBSDKernel

Compiling kernel

Rolling back to previous kernel