term% cat index.txt BOOT(8) System Manager's Manual 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 con‐
nects to the file server that will serve the root, performs any authen‐
tication 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 pro‐
gram. 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.
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 automati‐
cally 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 specified 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 encryp‐
tion 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: in‐
terface 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 simulating 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 /$objtype/init -t. If the -m
option is given it is also passed as an option to init.
If the kernel has been built with the cache file system, cfs(4), the
local disk partition /dev/[sh]d[01]cache exists, and the root file sys‐
tem is from a remote server, then the kernel will insert a user level
cache process between the remote server and the local namespace that
caches all remote accesses on the local partition. The -f flag com‐
mands cfs to reformat the cache partition.
CPU Servers
The user owning devices and console processes on CPU servers and that
user's domain and encryption key are read from NVRAM on all machines
except PC's. PC's keep the information in the disk partition
/dev/[sh]d[01]nvram. If a -k option is given or if no stored informa‐
tion is found boot will prompt for all three items and store them.
password:
authid: bootes
authdom: research.att.com
The key is used for mutual authentication of the server and its
clients. The domain and id identify the owner of the key.
Once connected, boot behaves as on the terminal except for exec(2)'ing
/$objtype/init -c.
Booting Methods
The methods available to any system depend on what was compiled 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 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)
BOOT(8)