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From: burgess@hrd769.brooks.af.mil (Dave Burgess)
Newsgroups: comp.os.386bsd.announce,comp.os.386bsd.questions
Subject: FAQ_03
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Date: 25 Apr 1993 16:12:22 -0700
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Section 3. (Kernel Building and Maintenance)
3.1 Kernel
One of the interesting aspects of 386bsd is the fact that it comes with
the complete source. This allows you to make changes to the system,
recompile, and test out your new ideas. This section of the FAQ
describes many of the different aspects of this endeavour and common
problems and pitfalls that are encountered. Kevin Lahey provided the
substantial portion of this section. You can contact him via E-Mail
at (kml@rokkaku.atl.ga.us) or contact Dave Burgess
(burgess@hrd769.brooks.af.mil).
3.1.1 How do I build a kernel?
The kernel can be compiled in a variety of ways to support
different devices and configurations. Compilation is controlled by a
config file that specifies the characteristics of the kernel.
A set of different config files is located in /sys/i386/conf.
The configuration file names are in upper case.
To build a particular kernel (in this example, we use the GENERICISA
configuration file):
% cd /sys/i386/conf
% config GENERICISA
% cd /sys/compile/GENERICISA
% make depend
% make
You'll need patch 1 from the patchkit to get the compilation to work,
'cause the version file isn't correctly included in the makefile.
3.1.2 I want to do one of the following things:
* add a device not in the distributed kernel (third com
port, additional disk or tape, line printer driver, etc).
* use a patch from the net or the patchkit to fix a kernel bug.
* add another swap device.
* recompile the kernel to remove extranious devices so that
it takes up less space.
* configure more pseudo-terminals to allow for more xterms
or network logins.
You're going to have to recompile the kernel after you modify the config
file.
3.1.3 I don't have the source distribution -- how can I rebuild the
kernel?
You can get the source for just the kernel from agate.berkeley.edu in the
directory /pub/386BSD/386bsd-0.1/filesystem/usr/src/sys.386bsd. In
addition, you will need to get a few include files, and make sure that
all of the files that are actually symbolic links point to the right
places. It is around five megs of source and maybe another meg compiled.
There are also reference sites available, as well as the 'good net-neighbor'
policy, whereby you could make arrangements with a net neighbor to use
a large local machine as a Network File System, or allow you to compile
a kew kernel on their machine and transfer it to yours. If you *still*
can't fit it in, you'll have to ftp a compiled kernel from agate in the
unofficial/patchkit-old directory or one of the archive sites. You can
also ask for help from comp.os.386bsd.questions if you get stuck and
cannot make any headway.
3.1.4 Now that I have a kernel, how do I install it?
Your kernel is called /386bsd. Copy the new kernel from
/sys/compile/GENERICISA/386bsd to /, assuming that it is in that directory.
This is relatively straightforward; there are a couple of things to
remember, though. First, if you really screw up the new kernel, you want
to have something to fall back on, so be sure to save /386bsd to
/386bsd.old before copying in a new kernel. Second, if you just copy the
new kernel over the currently running kernel, funny things can happen. Be
sure to move aside the currently running kernel before copying over the new
one.
There are folks that have reported that overwriting their current kernel
has never caused them any real problems. On the other hand, if the old
kernel was working and the new one doesn't, and you have made changes that
require that old kernel, it should be available to the system, and saving
it to /386bsd.alt or /386bsd.old are reasonable things to do.
If you are really paranoid, you can mount a new fixit floppy and replace
its kernel with the one you just built, and then boot from the fixit floppy
to make sure everything will work. This is a pretty good idea if you are
making radical changes or if you are unsure about your changes.
3.2 What exactly is this config file, anyway? What are all of
these cryptic notations?
I've annotated the distributed GENERICISA file; my comments are deliniated
by the '--' symbols.
#
# GENERICISA -- Generic ISA machine -- distribution floppy
#
--
BSD can be compiled for different hardware platforms, so it is important to
define the hardware types. 386bsd can only be built for 386 or
compatible machines, so this is sort of superflous, but maintains
compatibility with standard BSD config files.
--
machine "i386"
cpu "i386"
--
The ident describes the machine for which this kernel is to be built.
It is usually the system name -- "ROKKAKU", "REF", or whatever.
This can be used for conditional compilation, so that kernel changes
can be compiled in only for one machine.
--
ident GENERICISA
--
This should indicate the timezone of the system relative the
Greenwich. 8 is PST; 4 is EST. Somebody else might want to discuss
this more fully.
--
timezone 8 dst
--
maxusers isn't strictly checked; it is just used to size several
system data parameters.
--
maxusers 10
--
The options control the conditional compilation of features into the
kernel. The options can be listed all on a line separated by commas.
They are #define'ed when the kernel is compiled, so that #ifdef's
will work. An option can be given a value by appending an equals sign
and a value (enclosed in double quotes) to the option name.
Hopefully the names are at least somewhat self-explantory. To
discover what everything does, you'd have to go through the kernel
looking for all of the appropriate #ifdef's.
[Perhaps somebody else could list the *exact* meanings of these
options and some of the other possible options?]
--
options INET,ISOFS,NFS
options "COMPAT_43"
options "TCP_COMPAT_42"
--
The config line controls the location of the root, swap, and dump
devices. Anything not specified is defaulted. This is where you add
support for multiple swap devices. Just list 'em, separated by 'and'.
The config line below identifies the root drive as wd0 and the
swap drives as wd0 and as0. See the section on swap devices in FAQ_02
for additional information.
--
config "386bsd" root on wd0 swap on wd0 and as0
--
A 'controller' is a device or bus controller. 'isa' is obviously for
the ISA bus. 'wd0' is for regular disk controllers, 'fd0' is for the
floppies, and 'as0' is for SCSI disk controllers.
--
controller isa0
--
The fields work as follows:
a. What do you call this device?
b. What controller is this on? As you can see, the disk controller
talks to the ISA bus, and the disks talk to the disk controller.
c. Where are the registers for the controller mapped into memory?
This is #defined in /sys/i386/isa/isa.h.
d. What IRQ is this device set up for?
e. What routine should be called on an interrupt from the device?
a b c d e
vvv vvv vvvvvvv vv vvvvvv
--
controller wd0 at isa? port "IO_WD1" bio irq 14 vector wdintr
--
You need a 'disk' entry for every disk on the controller. In the
config file originally shipped with 386bsd, both hard disks were
incorrectly idenitified as wd0. Be sure to change the second occurence
to wd1, as I have done in below.
--
disk wd0 at wd0 drive 0
disk wd1 at wd0 drive 1
controller fd0 at isa? port "IO_FD1" bio irq 6 drq 2 vector fdintr
disk fd0 at fd0 drive 0
disk fd1 at fd0 drive 1
--
The 'drq' specifies the channel used for bus-mastering DMA??
--
controller as0 at isa? port 0x330 bio irq 11 drq 5 vector asintr
disk as0 at as0 drive 0
disk as1 at as0 drive 1
--
Define other physical devices. pc0 is the keyboard, npx0 drives the
math coprocessor, and com* controls the com ports.
--
device pc0 at isa? port "IO_KBD" tty irq 1 vector pcrint
device npx0 at isa? port "IO_NPX" irq 13 vector npxintr
device com1 at isa? port "IO_COM1" tty irq 4 vector comintr
device com2 at isa? port "IO_COM2" tty irq 3 vector comintr
--
Ethernet drivers of various sorts and the particular configuration
information they require.
--
device we0 at isa? port 0x280 net irq 2 iomem 0xd0000 iosiz 8192 vector weintr
device ne0 at isa? port 0x300 net irq 2 vector neintr
device ec0 at isa? port 0x250 net irq 2 iomem 0xd8000 iosiz 8192 vector ecintr
device is0 at isa? port 0x280 net irq 10 drq 7 vector isintr
--
Tape driver
--
device wt0 at isa? port 0x300 bio irq 5 drq 1 vector wtintr
--
The TCP/IP loopback device, ethernet interface, slip interface, log
device, and pseudoterminals.
--
pseudo-device loop
pseudo-device ether
pseudo-device sl 2
pseudo-device log
pseudo-device pty 4
--
Devices required by VM. Why are they here?
--
pseudo-device swappager
pseudo-device vnodepager
pseudo-device devpager
3.2.1 Okay, fine. Why shouldn't I just add every device I can find to
the kernel, so I'll never have to recompile this again?
Because it takes up space. The kernel is wired into memory, so every
byte it uses comes out of the pool of memory for everything else. It
can't page out sections that aren't in use. If your kernel is larger
than 640K, then it can't be loaded. You'll need to use Julian Elischer's
bootblocks to put it in high memory, which seem to be fairly complex.
Installing them (once they are compiled) is as easy as using disklabel.
3.2.2 What should I remove from the kernel?
What do you need? If you have a SCSI controller, you don't need the wd0
device; if you have another kind of disk controller, you don't need as0.
Unless you actually HAVE more than one Ethernet controller, you should
comment out all but one of them. If you don't have an ethernet controller,
you don't need any of the controllers or NFS compiled in. Without a
CD-ROM, ISOFS is kind of pointless. Just look at what you have and think
about what you really need.
3.2.3 I can't get enough remote login sessions or xterm sessions. What
can I do?
Increase the count of pseudoterminals --
pseudo-device pty 12 # or whatever
Every psuedo terminal should have a /dev/pty* entry. If you have 12
psuedo terminals, you should also have at least 12 pty devices in the
/dev directory. The MAKEDEV script in /dev will create up to 32 (?)
psuedo terminals automatically.
3.2.4 How do I get ddb, the kernel debugger, compiled into the kernel
and running?
Add the following line to the configuration file:
pseudo-device ddb
Build the kernel, then run dbsym on it:
% dbsym ./386bsd
Install it and go for it. Ctl-Alt-Esc drops you into the debugger.
3.2.5 Can I have more than one config file? Should I rename it to something
else? Any other hints?
You can create as many (or as few) config files as you desire. The system,
once the patchkit is applied, will have between 10 and 15, each of which
implements certain functions or features. In addition, the normal place
for the patchkit to make changes to the config files is in the
GENERICISA file. Since this file should remain unchanged and available,
it is always a good idea to copy this file to a meaningful name and
modify that file. In other words, change every reference in 3.1.1 from
GENERICISA to HAL (or whatever you call your system).
One final note. Every /sys/compile directory takes up 800K or so;
you might want to watch to see how big these all get.
3.2.6 Where can I learn more about all this?
We've skipped over alot of details here; the straight dope comes from
"Building Berkeley UNIX Kernels with Config", by Samuel J. Leffler and
Michael J. Karels.
3.3 X11/XFree86/XS3
3.3.1 What options should I define to get the X extensions included?
Once you have applied the patch kit, the only thing left to do is to
modify the config file to include the following line:
options XSERVER, UCONSOLE
recompile the kernel and the kernel should support X.
3.3.2 Where can I get the FAQ for 'X'?
The 'X' FAQ is posted to comp.os.386bsd.apps at regular intervals, as
well as news.answers, comp.answers, and several other places. It
is also available for anonymous FTP at rtfm.mit.edu in the ???
directory.
3.4 Compiler and Library routines
[ this was really an empty section! -- cgd ]
--
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