ROM files allow specification of runtime options for protocols and various subsystems. When a protocol instance or x-kernel subsystem initializes, it typically scans a list of user-provided options in the ROM file to see if it should adjust its default parameters for that particular instantiation. ROM options are used for a variety of purposes, such as providing initial values for databases, specifying numbers of network shepherd threads, and providing IP gateway information.
Each ROM file entry consists of a single line. The first field in each line specifies the particular protocol or subsystem that should interpret that line. The rest of the fields are specific to that particular protocol or subsystem. Comments can be added following a #. For example, given the following ROM file:
#
# Example ROM file
#
simeth port 1234
arp 192.12.69.49 192.12.69.1 1234
arp 192.12.69.45 192.12.69.1 9876
prottbl /usr/xkernel/etc/prottbl.nonstd
the SIMETH protocol will interpret the first line, the ARP protocol will interpret the second and third lines, and the protocol table subsystem will interpret the last line.
The exact method for indicating where the x-kernel should find its ROM files is specific to the individual platforms and is documented for each platform in Section 12.6.
Protocols that provide ROM file configurable options will describe the format of these options in their man pages in Appendix A.