Kernel Image Parameters - Sun Microsystems Sun Workstation 100U System Manager's Manual

Building Sun Workstation Kernels
Configuration File Syntax
2.2. Kernel Image Parameters
Multiple bootable images may be specified in a single configuration file. The kernels will have
the same global configuration parameters and devices, but the location of the root file system
and other kernel-specific devices may be different. A kernel image is specified with a "config"
line:
config kername config-clau&e&
The kername field is the name given to the loaded kernel image; the standard kernel image is
"vmunix". The configuration clauses are one or more specifications indicating where the root
file system is located, how many paging devices there are and where they go.
A configuration clause is one of the following
root [ on ] root-device
swap [ on ] 6wap-device [ and swap-device]*
dumps [ on ] dump-device
args [ on ] arg- device
(the "on" is optional.) Multiple configuration clauses are separated by white space; config
allows specifications to be continued across multiple lines by beginning the continuation line
with a tab character. The "root" clause specifies where the root file system is located, the
"swap" clause indicates swapping and paging area(s), and the "dumps" clause can be used to
force crash dumps to be taken on a particular device, and the "args" clause can be used to
specify that argument list processing (or execve should be done on a particular disk.
The device names supplied in the clauses may be fully specified - as a device, unit, and file sys-
tem partition - or underspecified. If underspecified, config will use builtin rules to select
default unit numbers and file system partitions. The defaulting rules are dependent on the
overall system configuration. For example, the swap area need not be specified at all if the root
device is specified; in this case the swap area is placed in the "b" partition of the same disk
where the root file system is located. Appendix B contains a complete list of the defaulting
rules used in selecting devices.
The device names are translated to the appropriate major and minor device numbers on a per-
machine basis.
A file, / sys/ conl/ devices.machine (where "machine" is the machine type
specified in the configuration file), is used to map a device name to its major block device
number. The minor device number is calculated using the standard disk partitioning rules.
If the default mapping of device name to major/minor device number is incorrect (or your
configuration, it can be replaced by an explicit specification of the major/minor device. This is
done by substituting
major x minor y
where the device name would normally be found. For example,
config vm unix root on major gg minor 1
Normally, the areas configured for swap space are sized by the kernel at boot time. If a non-
standard partition size is to be used for one or more swap areas, this can also be specified. To
do this, the device name specified for a swap area should have a "size" specification appended.
For example,
config vmunix root on xyO swap on xyOb size 12000
would force swapping to be done in partition "b" o( "xyO" and the swap partition size would be
set to 1200 sectors. A swap area sized larger than the associated disk partition is trimmed to
the partition size.
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