A few kernel options are of specific interest to those creating an embedded FreeBSD system.

All embedded FreeBSD systems that use flash memory as system disk will be interested in memory disks and memory filesystems. Because of the limited number of writes that can be done to flash memory, the disk and the filesystems on the disk will most likely be mounted read-only. In this environment, filesystems such as /tmp and /var are mounted as memory filesystems to allow the system to create logs and update counters and temporary files. Memory filesystems are a critical component to a successful solid state FreeBSD implementation.

You should make sure the following lines exist in your kernel configuration file:

options         MFS             # Memory Filesystem
options         MD_ROOT         # md device usable as a potential root device
pseudo-device   md              # memory disk