Once the kernel is loaded by either loader (as usual) or boot2 (bypassing the loader), it examines its boot flags, if any, and adjusts its behavior as necessary.
Here are the more common boot flags:
-aduring kernel initialization, ask for the device to mount as the root file system.
-Cboot from CDROM.
-crun UserConfig, the boot-time kernel configurator
-sboot into single-user mode
-vbe more verbose during kernel startup
Note: There are other boot flags, read boot(8) for more information on them.
This, and other documents, can be downloaded from ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/.
For questions about FreeBSD, read the documentation before contacting <questions@FreeBSD.org>.
For questions about this documentation, e-mail <doc@FreeBSD.org>.