Minix1.1/user/doc/READ_ME
The book went to press before the software, so last-minute changes are noted
here. In particular, after the book went to press, the software was ported
to the PC/AT and various PC clones, which necessitated some minor patches
here and there.
1. GENERAL
There were a number of minor changes made to the code after the book
was printed, as mentioned above. As a result, line X of file Y in the
book may actually appear at X+3, or X-5, etc. on the disk version.
2. HARD DISK
MINIX supports the use of the standard IBM hard disk. To use a
hard disk with MINIX, you need one or more MINIX partitions. You may
also have MS-DOS, PC-IX, XENIX, or other partitions as well if you like.
If you have a version of FDISK that is able to make several partitions,
do so, reserving one for MINIX. If not, you can make several partitions
as follows:
1. Backup all the files on the entire hard disk to floppies.
2. Run FDISK to delete all partitions and make a partition for MINIX.
3. Run diskfix (see below) to mark the new partition as type MINIX.
4. Run FDISK to make a new MS-DOS partition (optional).
5. Restore the files on the MS-DOS partition.
6. Boot MINIX and make a MINIX file system on its partition (see below).
The basic problem with MS-DOS FDISK is that it can only make one MS-DOS
partition and nothing else. It is not very flexible. Therefore diskfix
is needed to mark the one partition as non-DOS, so that FDISK will be
willing to make another one. Diskfix.asm is a MASM (assembly code) program
located in the MINIX tools source directory. Copy it to an MS-DOS disk
using doswrite, then assemble it. When it runs, it reads in the partition
table, changes all partitions to non-DOS type, and writes it back.
Once you have a partition available for MINIX (the type does not matter
as MINIX does not check), make a file system by booting MINIX from floppy
the usual way and run mkfs. If, for example, you have chosen partition 2,
which has, say, 40 cylinders (i.e., 40 x 68 = 2720 sectors or 1360 1K
blocks), type:
mkfs /dev/hd2 1360
to make an empty file system. However, for partition 1 use 1 block less
because block 0 is not available (it contains the MS-DOS partition table).
In other words, a 40 cylinder partition 1 has 1359 blocks but a 40 cylinder
partition 2 or higher has 1360 blocks. Then mount the file system by typing:
/etc/mount /dev/hd2 /user
Next, make whatever directories you like, typically bin, lib, and others,
and copy files to the hard disk. With the /usr floppy in drive 0, the
command
cp /usr/bin/* /user/bin
will copy all the binaries from /usr/bin to the hard disk, for example.
Finally, edit /etc/rc to have the hard disk mounted when the system
is booted. A line such as
/etc/mount /dev/hd2 /usr
can be used as a replacement for the mount command initially in /etc/rc.
After editing /etc/rc, mount the root file system diskette and copy it
to the diskette; otherwise the changes will be lost when the system is
rebooted. (There is nothing special about the root file system except
its size; it can be mounted and written on like any other file system.)
After these steps have been taken, the system can be booted from
floppy in the usual way, and the root file system also read in from
floppy. The hard disk will automatically be mounted by the /etc/rc.
The root device remains on the RAM disk, and the boot process still
goes via floppy (for compatibility and to prevent disaster in the event
that something goes wrong with the hard disk file system). Hard disk
file systems can be checked using fsck by typing 'x' or 'a' when the
initial menu is display.
The special file /dev/hd0 refers to the whole disk, without regard to
partitions, whereas /dev/hd1 ... /dev/hd4 refer to partitions 1 to 4. If
you have a second hard disk, you can make /dev/hd5 ... /dev/hd9 with mknod
(major device 3, minor device 5 ... 9) for the second drive, with hd5 for
the whole drive, hd6 for partition 1, etc. Fsck also uses this convention.
The MINIX program mkfs writes a file system on whatever partition you
tell it to. If you tell it to use partition 2, it does. Consequently, a
typing error here can result in erasing all your files. (In MS-DOS typing
del *.c instead of del *.o will remove all the sources instead of all the
object files.) Therefore, it is strongly recommended that you back up
your entire hard disk before installing MINIX. Better safe than sorry.
Many hard disks are used on IBM PCs, XTs, and ATs. Each one needs a
different driver. The files xt_wini.c and at_wini.c are drivers for the
standard IBM XT and AT disks respectively. Their drivers are totally
different. When generating a new system, you must copy the appropriate
driver to the file wini.c (in the kernel directory) depending on whether
you have a PC or XT (use xt_wini.c) or an AT (use at_wini.c). You MUST
choose one of these drivers even if you have no hard disk at all.
3. PC/AT
The distribution for the PC/AT differs from that for the PC in minor
ways. For example, there is no /user diskette. All the files that would
normally be on /user fit on /usr. Furthermore, the number and organization
of the source diskettes is different, but the same programs are available.
Source diskette 1 has been arranged so that it can be mounted and you can
change to the kernel, mm, or fs directory, and just type make to compile.
Two additional special files are present in /dev: /dev/at0 and /dev/at1.
These should be used to access 1.2M diskettes. To access 360K diskettes
on the PC/AT, use /dev/fd0 and /dev/fd1. Special files are used by
commands such as mount, mkfs, and df, among others. For example, to
copy part of a 1.2M diskette, type dd if=/dev/at0 of=file count=100.
The difference between /dev/at0 and /dev/fd0 is that in MINIX, special
files have sizes to prevent access beyond the end. For /dev/fd0 the
size is 360K. For /dev/at0 it is 1.2M.
4. USING MS-DOS AS A DEVELOPMENT SYSTEM
The conversion of MINIX to make it possible to use MS-DOS as the
development system was done by Paul Ogilvie. It was done in order to
to provide some assistance to people who wish to modify MINIX but
are unable to use MINIX or UNIX for that purpose. MS-DOS definitely should
be regarded as the method of last resort, only used if there is no other
alternative. The assembly code files and batch files provided have all
been tested with the Computer Innovations C86 compiler, release 2.4, and
specific versions of the linker etc. The use of any other compiler or
configuration is virtually guaranteed not to work the first time because
every MS-DOS C compiler is different, their libraries are different, etc.
MS-DOS users must approach this project with the expectation that minor
problems will arise and small patches to the code may be needed to work
around bugs and deficiencies that abound with MS-DOS compilers. When
problems appear with files that are different for MS-DOS and MINIX,
check the MINIX version, since these have been tested much more
thoroughly than the MS-DOS versions.
5. BUGS in MS-DOS
Some machines and/or versions of MS-DOS have a bug when doing absolute
diskio, as used by mkfs and build. This bug will manifest itself by
creating an unbootable disk, saying a file-system is bad, or sometimes
the program will just hang. The primary remedy if your machine suffers
from this bug is to first format the disk. A permanent remedy is to
change the module "diskio.asm" to use bios I/O calls instead of using the
DOS interrupts 25 and 26 (see fsck1.asm). Disadvantage of the latter is
that you cannot extend these programs anymore to work on a hard disk (e.g.
making a MINIX filesystem on a hard disk).
Though the cause is not clear, it is assumed that these DOS system calls
don't know if they should read/write an 8 sector per track diskette or a 9
sector per track diskette. Formatting the disk will make clear to DOS that
they should do 9 sectors per track. MINIX does not support 8 sectors per
track at all.
6. BATCH FILES in MS-DOS
The batch jobs are all made for a system with a hard disk.
Depending on your floppy configuration you can modify them to ask for the
necessary diskettes. When linking, the jobs expect a directory \lib\c86
where they can find the DOS-library for C86 (the C86s2s library for small
model, DOS-2, software floating point). In any event, all MS-DOS users
should carefully inspect all the batch files before using them.
In DOS version 2.x, the 'echo'-command behaves somewhat different
than in DOS version 3.x. The difference is is how to echo a new line to
the screen. With Dos-2 you can do this by appending three spaces to the
command, e.g. 'echo ' and with Dos-3 you can do this by the command
'echo/'. Unfortunately both things aren't documented and are not compatible
and will just say "ECHO is on" (or off). Appart from clobbering your
screen nothing is wrong. The batch files on this disk are for DOS version 3.
7. MS-DOS ASSEMBLER
The Microsoft masm manual is not very clear about when you must use
group-directives. The files included in this distribution work, but in
general, be careful.
8. STATIC DECLARATIONS
The MINIX C compiler puts static variables in the data segment, not
the bss segment. This increases the size of the a.out file on the disk.
Thus it is better to avoid declaring large arrays as static. Futhermore,
because the assembler reads all the .s files at once, the use of static
to make it possible to re-use the same name in two files does not work.
All global names must be unique. Thus putting static x; in two files will
not work.
9. MAKING MINIX ON PC/AT
The book says that you should put each directory (kernel, mm, fs, etc.)
on a separate diskette. With the 1.2M diskettes, you can keep kernel,
mm and fs on the same diskette, provided that you remove all the irrelevant
files (such as library sources), and avoid unnecessary files. Hard disk too.
When making MINIX on a PC/AT with one floppy disk drive, you will have
to put the image file on the same diskette as build. The trick is then
to get it onto the boot diskette, starting at block 0. The only way is
first to build a new root file system containing an almost empty RAM disk
of about 200K. Construct a proto file for mkfs containing in bin: sh, cp,
sync, and getlf, as well as etc with mount, umount, passwd, rc, ttys, and
message. The dev directory should contain the usual files. An empty usr
directory is also needed. Once you have the image file in tools and the
new root file system, proceed as follow.
1. Shut down the system.
2. Reboot MINIX, using the almost empty 200K file system.
3. Mount the diskette containing tools on /usr.
4. Copy image to /.
5. Unmount the tools diskette.
6. Insert a blank diskette.
7. Copy /image to /dev/at0.
This diskette is your new boot diskette.
10. MOVING MINIX SOURCES TO NON-MINIX SYSTEMS
The source disks are distributed as MINIX file systems, ready to mount.
To read them under MS-DOS or PC-IX they must first be converted.
To move the MINIX sources to some other system on a computer with only
one floppy disk drive, first remove as many files as possible from the
RAM disk, and copy the files to be moved to the RAM disk. Then insert
a diskette and copy the files to the diskette. One possibility is using
doswrite. Another is to make a shar archive and write it directly on
/dev/fd0. This can then be copied byte for byte to another system and
unpacked with the shell. Alternatively, ar.c can first be copied to a
diskette all by itself to get it to another machine, where it can be
compiled. Subsequent files can be transferred in ar format. On a computer
with two disk drives, both the MINIX and "foreign" file system can be
present at once.
11. EDITING LARGE PROGRAMS WITH MINED
Mined has a limit on the size of programs it can edit. To edit
larger ones, they must be broken up with split, edited separately and
recombined later. If a file is too large, mined will issue an error
message and exit.
12. MKNOD
MINIX differs from UNIX in that block special files (and even some
character special files, such as /dev/kmem) can have sizes. A 360K floppy
disk special file, such as /dev/fd0 can have size 360K. Unfortunately, the
mknod system call (and mknod program) have no way to express the size,
so it uses size 0, which is equal to infinity. When you read past the
end of a block special file WITH a size, the file system returns zero
bytes. When you go off the end of a device WITHOUT a size, some drivers
return end-of-file (e.g., hard disk, RAM disk), but others (e.g., floppy
disk) return an I/O error code. Thus if you make a new block special file
for 2/0 and 2/1 (floppy disk) with mknod (i.e., no size) the command
cp /dev/fd0 /dev/fd1
will terminate with an error on block 360 (but it will copy the disk
perfectly). The only way to make a special file with a size is by making
a file system with mkfs.
13. NONEXISTENT DEVICES
If you try to open /dev/fd1 on a system with only one floppy disk drive,
the system may hang. To avoid this problem, the first time you log in, go
to the /dev directory, and rename special files that you do not have to
something unusual. For example, if you do not have a hard disk, rename
hd0 to HARD_DISK_0, hd1 to HARD_DISK_1, etc. Similarly with one one floppy
disk, rename fd1 to FLOPPY_DISK_1 to prevent it being typed by accident.
You can also remove them, but due to the mknod problem described above, you
can not get them back easily, so it is best just to get them out of the
way in case you ever need them again later.
14. PRINTER
In order to accommodate buffered and unbuffered printers, the printer
driver uses a combination of delay loops and interrupts. The net result
is that the driver consumes a fair number of CPU cyles when running. If you
expect to do a lot of printing, you might want to consider rewriting the
printer interrupt handler, pr_char, in assembly code.
15. DISK SPACE
The /usr disk as distributed is entirely full. If you have two floppy
disk drives, be sure to mount /user on drive 1 and move your working
directory there. If you have only 1 floppy disk drive, remove some files
from /usr/bin to make more space.
16. RUNNING /USER TESTS
Before running the tests in /user/test, remove the files in
/user/commands to create some free space on the disk.
17. COMMAND LINE LENGTH
The maximum initial stack size is 1K. Calls to EXEC which require a
larger stack will fail. Thus if you try to do ls -l * in a large directory,
the shell may expand the * so that the command line exceeds 1K and the
EXEC will fail, resulting in the message "Cannot execute ls".
18. 8086 TIMING PROBLEMS
There may be some weird (timing?) problems on PC clones using 8086 chips.
This seems strange, because on the IBM PC-AT everything works perfectly. If
anyone can find the cause of the problems (or for that matter, any other
problems) let me know via Prentice-Hall or comp.os.minix (news) or
minix@cs.vu.nl (mail).