boot.8

操作系统设计与实现源码

.TH BOOT 8
.SH NAME
boot \- from power on to the login prompt
.SH DESCRIPTION
.de SP
.if t .sp 0.4
.if n .sp
..
At power on the machine reads the first sector of the boot device into memory
and executes it.  This bootstrap code loads
.BR /boot ,
the Minix Boot Monitor.  The monitor loads the kernel binaries from
.BR /minix ,
or the newest file in
.B /minix
if it is a directory.
.PP
The Minix system is now running, the different tasks initialize themselves
and control is transferred to the last one,
.BR init .
.PP
.B Init
is the grandparent of all Minix processes, it is responsible for starting
login processes on each terminal, but first it runs
.BR /etc/rc .
.PP
.B /etc/rc
checks the state of the system and starts daemons.  First it sets the
keyboard translation to the mapping in
.B /etc/keymap
if present, then it reads the time zone from
.B /etc/timeinfo
followed by a call to
.BR readclock (8)
to set Minix time from the hardware clock.  Next the file systems are checked
if necessary and the
.B /usr
file system is mounted.
.PP
The system is now ready for multiuser startup,
.B /etc/rc
starts the
.BR update (8)
and
.BR cron (8)
daemons, and initializes the network services.
.B /etc/rc
finally recovers crashed editor buffers and cleans out the
.B tmp
directories.
.PP
.B Init
reads
.B /etc/ttytab
and starts a
.BR getty (8)
for each enabled terminal line to allow a user to log in.
.SH "BOOT ENVIRONMENT"
Many features of the drivers inside the kernel are controlled by settings in
the boot environment.  The values of these variables are usually colon or
comma separated numbers configuring the driver.
.B "DPETH0 = 300:10"
tells the ethernet driver to use I/O address 0x300, interrupt request
10, and the default memory address (0xD0000, values may be omitted) for the
first ethernet board.  (Note that IRQ 2 is redirected to IRQ 9 on AT's and
PS/2's, so use 9 if a device is jumpered for 2.)
.PP
Variables that are special to both the monitor and the kernel are described
in
.BR monitor (8).
This section lists extra variables or variable settings:
.TP
\fBhd\fR = \fBat\fR | \fBbios\fP | \fBesdi\fR | \fBxt\fR
Choose the driver that is to be used for the hard disk, in order: IBM/AT
(classic AT or newer IDE), BIOS (generic driver), ESDI (some PS/2's), or
IBM/XT.  By default the first of these drivers that is enabled is used.
Most drivers are present in the kernel as distributed, but may be taken out
by modifying
.BR /usr/include/minix/config.h .
(An XT should always use the BIOS driver, not the XT driver, because BIOS
calls are cheap on an XT.  The XT driver can be used on AT machines with an
old XT controller.)
.TP
\fBDPETH\fIn\fR = \fBon\fR | \fBoff\fR
Turn an ethernet board on or off.  The driver is by default in "sink" mode
for all boards.  The sink mode allows one to use the driver without an
ethernet board installed.  The driver will play /dev/null for that device,
i.e. nothing comes in, and anything send out is dropped on the floor.  If
the board is turned on then the driver will use it to send out packets, if
it is turned off then the driver will fail for that board.
.TP
\fBDPETH\fIn\fR = \fII/O-addr\fR:\fIirq\fR:\fImem_addr\fR
Set the I/O address (hex), IRQ (decimal) and memory address (hex) of the
.IR n -th
ethernet board and turn it on.  By default they are configured as
280:3:D0000 and 300:5:CC000.  The memory address is ignored for the Novell
ethernet boards, but may be explicitly set to zero to indicate that the board
.B is
a Novell ethernet board.  You do not need to specify the IRQ with modern
Western Digital 8013 compatible ethernet cards, the driver asks the board
what its IRQ is.
(Note that the default IRQ conflicts with the second serial line, so the
serial line is turned off if the ethernet board is configured for IRQ 3.)
.TP
\fBDPETH\fIn\fB_EA\fR = \fIe0\fR:\fIe1\fR:\fIe2\fR:\fIe3\fR:\fIe4\fR:\fIe5\fR
Set the ethernet address of the
.IR n -th
ethernet board.  The address is normally obtained from the ethernet board,
so only in exceptional circumstances is this setting ever needed.  (Use the
address of the main server if you want a career change.)
.TP
\fBAHA0\fR = \fII/O-addr\fR:\fIbus-on\fR:\fIbus-off\fR:\fItr-speed\fR
Configure the Adaptec 154xA SCSI host adapter to use the given I/O address
(hex), Bus-on time (decimal), Bus-off time (decimal) and transfer speed
(hex).  The default is 330:15:1:00.  The default transfer speed is always
5.0 Mb/s (code 00) ignoring the jumper settings.
.TP
\fBsd\fIn\fR = \fItarget\fR,\fIlun\fR
Program SCSI disk
.BI sd n
to have the given target and logical unit number.  The target and lun
of a tape or other SCSI device may be changed by setting the
.BI sd n
variable that would be used had it been a disk.  So tape device st7 can be
set to target 4, lun 1 with sd35=4,1.
.TP
\fBMCD\fR = \fII/O-addr\fR:\fIirq\fR
I/O address (hex) and IRQ (decimal) of the Mitsumi CD-ROM driver, by default
300:10.
.SH "TCP/IP CONFIGURATION"
To use TCP/IP you have to compile a kernel with networking enabled, and
unless you are running standalone you have to enable the ethernet driver.
See the
.BI DPETH n
boot variable above.  The driver supports these ethernet cards:  Western
Digital 8003, Western Digital 8013, SMC Elite Ultra 16, Novell NE1000,
Novell NE2000.  Many newer variants of the WD8013, now under the SMC brand,
are also supported.
.PP
You are likely to use TCP/IP in one of three situations:
.PP
.RS
Standalone with no connection to a network.
.SP
In a small network with no support from a "big" host.
.SP
Connected to a large network with address and name servers.
.RE
.PP
In each situation you need a different set of configuration files.
.SS Standalone
The machine is configured with a fixed IP address:
.BR 192.9.200.1 .
This is one of the addresses Sun used to give to machines without a
registered network address.  This address is normally blocked at gateways,
so it can do no damage if used in a real net by accident.  You need one
file,
.BR /etc/hosts ,
that should look like this (using the name "darask" as an example):
.PP
.RS
.ta +15n
127.0.0.1	localhost
.br
192.9.200.1	darask
.RE
.SS "Small Network"
In a network where the Minix machine can't obtain its IP address and name
from a different host you need specify the ethernet address to host name
translation in the
.B /etc/ethers
file for use by the RARP daemon.  Suppose you have two machines in your
network then
.B /etc/ethers
could look like this:
.PP
.RS
.ta +20n
0:0:c0:a:77:23	darask
.br
0:0:c0:a:68:ce	burask
.RE
.PP
Use
.B hostaddr \-e
to find out what the six octet ethernet address of a host is.  Use the address
as printed: lowercase hex digits, no leading zeros.  The
.B /etc/hosts
file shows their IP addresses:
.PP
.RS
.ta +15n
127.0.0.1	localhost
.br
192.9.200.1	darask
.br
192.9.200.2	burask
.RE
.PP
.B Warning!
Do not add ethernet addresses of diskless workstations to your ethers file.
A Sun for instance has the stupid habit of booting from the first RARP server
that answers, probably your Minix machine...
.SS "Large Network"
In a network with a central network administration your machine's IP address
and name are given by the RARP and name services of the special servers on
the network.  For a new machine you need to apply for an IP address and host
name with your network administrator supplying the ethernet address of your
machine.  You don't need any configuration files now, the
.B irdpd
and
.B nonamed
daemons automatically find a router and a name server.
.PP
Note that no knowledge of the IP address or hostname of the Minix machine
itself is necessary, it all comes from the RARP and name servers.  A series
of Minix machines can therefore set up identically.  Even if you have no RARP
or name servers you can still set them up identically if you list all the
Minix hosts in the hosts and ethers files.
.SS "Simpler configuration tools"
The
.BR rarpd ,
.BR irdpd
and
.BR nonamed
daemons are complex little programs that try to obtain information about
their surroundings automatically to tell the machine what its place in the
network is.  It should come as no surprise that there are simpler utilities
to configure a machine.  On a memory starved machine it may even be wise to
configure a machine statically to get rid of the daemons.  The first daemon,
.BR rarpd ,
can be replaced by:
.PP
.RS
.B ifconfig \-h
.I host-IP-address
.RE
.PP
to set the IP address of the machine.  Note that this is only necessary if
there is no external RARP service.  The second daemon
.B irdpd
can be replaced by setting a static route:
.PP
.RS
.B add_route \-g
.I router-IP-address
.RE
.PP
(if there is a router.)  The last daemon,
.BR nonamed ,
can be replaced by an entry in
.B /etc/resolv.conf
that specifies an external name daemon:
.PP
.RS
.B nameserver
.I nameserver-IP-address
.RE
.PP
The
.B ifconfig
and
.B add_route
calls can be placed in the file
.BR /etc/rc.net .
The calls to the daemons will have to be edited out of
.BR /etc/rc .
Note that these changes undo all the efforts to make Minix TCP/IP
autoconfigurable.  Make very sure that all the IP addresses are correct, and
that the IP address of your machine is unique.  (Mistakenly using the
address of a main server will make all other machines look at your machine,
and will make all the users of all other machines look at you.)
.SH FILES
.TP 20n
/boot
Minix Boot Monitor.
.TP
/minix
Kernel image, or directory containing them.
.TP
/etc/rc
First of the system initialization files.
.TP
/etc/hosts
Name to IP address mapping.
.TP
/etc/ethers
Name to ethernet address mapping.
.SH "SEE ALSO"
.BR monitor (8),
.BR init (8),
.BR inet (8),
.BR loadkeys (8),
.BR readclock (8),
.BR fsck (1),
.BR update (8),
.BR cron (8),
.BR ttytab (5),
.BR getty (8),
.BR hostaddr (1),
.BR ifconfig (8),
.BR irdpd (8),
.BR nonamed (8),
.BR rarpd (8),
.BR hosts (5),
.BR ethers (5),
.BR set_net_default (8).
.SH DIAGNOSTICS
.TP 5n
Checking File Systems.
If the system has crashed then
.B fsck
is called for the root and /usr file systems.  It is wise to reboot if the
root file system must be fixed.
.TP
Finish the name of device to mount as /usr: /dev/
If the name of the /usr file system has not been set in /etc/fstab.
You can type a device name, say
.BR fd0 .
.TP
hostaddr: unable to fetch IP address
TCP/IP misconfiguration.  The RARP may have failed because the ethernet
address of the machine is not entered in either the remote or the local
ethers file.  Either talk to your Network Administrator, or make an ethers
and a hosts file.
.TP
1.2.3.4 login:
If you see an IP address instead of a host name then the system failed to
translate the IP address.  Either talk to your Network Administrator to
have the reverse address translation tables fixed, or make a hosts file.
.SH NOTES
The names "darask" and "burask" are names of cities from the Dutch
translation of the novel "The Many-Colored Land" by Julian May.  The author
of this text likes names of hosts to be things that contain people, like
cities and ships.
.SH BUGS
Indefinite hangs are possible if I/O addresses or IRQ's are wrong.  A driver
may babble about addresses and IRQ's, but that does not mean that what it
says is true, it may just be configured that way.  It is very difficult to
find peripherals on a PC automatically, and Minix doesn't even try.
.SH AUTHOR
Kees J. Bot ([e-mail])