BOOT(8) BOOT(8)
NAME
boot - connect to the root file server
SYNOPSIS
/boot [ -fkm ] [ -uusername ] [ method!fs-addr ]
DESCRIPTION
Boot is the first program run after a kernel has been
loaded. It connects to the file server that will serve the
root, performs any authentication needed to connect to that
server, and exec(2)'s the init(8) program. It is started by
the kernel, never run directly by the user. See booting(8)
for information about the process of loading the kernel (and
boot) into memory.
Once loaded, the kernel initializes its data structures and
devices. It sets the two environment variables /env/cputype
and /env/terminal to describe the processor. It then binds
a place-holder file server, root(3), onto / and crafts an
initial process whose sole function is to exec(2) /boot, a
binary which is compiled into root(3).
The command line passed depends on the information passed
from boot ROM to kernel. On the MIPS Magnum and SGI Power
Series the command line passed to boot is the same as that
given to the ROM monitor.
On AT&T Gnots the command line is
/68020/9gnot method!server
On the Nextstation , no information is passed from the boot
ROM or program. The command line is
/68020/9nextstation
On the PC, each line in the DOS file plan9.ini of the form
name=value is passed to the boot program as an environment
variable with the same name and value. The command line is
/386/9pc method!server
Boot must determine the file server to use and a method with
which to connect to it. It must also set a user name to be
used as the owner of devices and all console processes and
an encryption key to be used when challenged. Boot will
prompt for these.
Method and address are prompted for first. The prompt lists
all valid methods, with the default in brackets.
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BOOT(8) BOOT(8)
root is from (il, tcp, hs, local)[il]:
A newline picks the default. Other possible responses are
method or method!address. To aid in automatic reboot, the
default is automatically taken on CPU servers if nothing is
typed within 15 seconds.
The other interactions depend on whether the system is a
terminal or a CPU server.
Terminal
The terminal must have a username to set. If none is speci-
fied with the -u option, boot will prompt for one on the
console:
user:
The user will also be prompted for a password to be used as
an encryption key on each attach(5):
password:
With most methods boot can now connect to the file server.
However, with the serial line methods 9600 and 19200, the
actual mechanics of setting up the complete connection are
too varied to put into the boot program. Instead boot lets
the user set up the connection. It prints a prompt on the
console and then simulates a dumb terminal between the user
and the serial line:
Connect to file system now, type ctrl-d when done.
(Use the view or down arrow key to send a break)
The user can now type at a modem or a Datakit destination
please: interface to set up the connection to a TSM8 card.
At Murray Hill, a user would type nj/astro/plan85 at this
point. When the user types a control-D, boot stops simulat-
ing a terminal and starts the file system protocol over the
serial line.
Once connected, boot mounts the root file system before /
and makes the connection available as #s/boot for subsequent
processes to mount (see bind(2)). Boot completes by
exec(2)'ing /$objtype/init -t. If the -m option is given it
is also passed as an option to init.
If the kernel has been built with the cache file system,
cfs(4), the local disk partition /dev/[sh]d[01]cache exists,
and the root file system is from a remote server, then the
kernel will insert a user level cache process between the
remote server and the local namespace that caches all remote
accesses on the local partition. The -f flag commands cfs
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BOOT(8) BOOT(8)
to reformat the cache partition.
CPU Servers
The user owning devices and console processes on CPU servers
and that user's domain and encryption key are read from
NVRAM on all machines except PC's. PC's keep the informa-
tion in the disk partition /dev/[sh]d[01]nvram. If a -k
option is given or if no stored information is found boot
will prompt for all three items and store them.
password:
authid: bootes
authdom: research.att.com
The key is used for mutual authentication of the server and
its clients. The domain and id identify the owner of the
key.
Once connected, boot behaves as on the terminal except for
exec(2)'ing /$objtype/init -c.
Booting Methods
The methods available to any system depend on what was com-
piled into the kernel. The complete list of booting methods
are listed below.
cyc connect via a point-to-point fiber link using
Cyclone boards. If specified, the address must be
the number of the Cyclone board to be used, default
0.
il connect via Ethernet using the IL protocol.
tcp connect via Ethernet using the TCP protocol. This
method is used only if the initial file server is on
a Unix system.
hs connect via Datakit using the high speed Datakit
card.
incon connect via Datakit using the Incon interface.
9600 connect via Datakit using the serial interface at
9600 baud.
19200 connect via Datakit using the serial interface at
19200 baud.
local connect to the local file system.
For the il and tcp methods, the address must be a numeric IP
address. If no address is specified, a file server address
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will be found from another system on the network using the
BOOTP protocol and the Plan 9 vendor-specific fields. For
the Datakit methods, hs, 9600, 19200, and incon, the address
must be specified and must be a relative path name to the
file server. If no address is specified, the address Nfs is
used.
FILES
#s/boot
SOURCE
/sys/src/9/boot
SEE ALSO
root(3), bootp(8), init(8)
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