boot man page on Plan9

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BOOT(8)								       BOOT(8)

       boot - connect to the root file server

       /boot/boot [ -fkm ] [ -uusername ] [ method!fs-addr ] [ args ]

       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/boot, a binary which is compiled into root(3).

       The command line passed depends on the information passed from boot ROM
       to  kernel.   Machines  that  boot  directly  from  ROM	(that is, most
       machines other than PCs) pass the boot line given to the	 ROM  directly
       to boot.

       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

	      /386/9dos method!server

       (The  first argument is ignored by boot.)  Boot must determine the file
       server to use and a method with which to connect to it.	Typically this
       will  name  a  file  server on the network, or state that the root file
       system is on local disk and name the partition.	The complete  list  of
       methods is given below.

       Boot  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, for example:

	      root is from (tcp, local!#S/sdC0/fs)[tcp]:

       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.

       The  terminal  must  have a username to set.  If none is specified with
       the -u option, boot will prompt for one on the console:


       The user will also be prompted for a password to be used as an  encryp‐
       tion key on each attach(5):


       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 the modem to dial the number.  What  is	 typed
       depends on the modem and is beyond this discussion.

       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 /$cputype/init -t.  If the  -m
       option  is  given it is also passed as an option to init.  If the envi‐
       ronment variable init is set (via plan9.ini(8)), it is used as  a  com‐
       mand line to exec instead.

       If  the	kernel	has been built with the cache file system, cfs(4), the
       local disk partition /dev/sdXX/cache (where XX  is  a  unit  specifier)
       exists, and the root file system is from a remote server, then the ker‐
       nel 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 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/sdXX/nvram.	  If  a -k option is given or if no stored information
       is found boot will prompt for all three items and store them.

	      authid: bootes

       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
       /$cputype/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.

       tcp     connect	via  Ethernet  using  the  TCP protocol.  The args are
	       passed to ipconfig(8)  when  configuring	 the  IP  stack.   The
	       plan9.ini(8) variables fs and auth override the file server and
	       authentication server IP addresses obtained (if any) from  DHCP
	       during ipconfig(8).

       local   connect to the local file system.  The first argument is a disk
	       holding a file system.  Boot inspects the disk.	If the disk is
	       a  fossil(4)  file system, it invokes /boot/fossil to serve it.
	       If the venti environment variable (really,  plan9.ini(8)	 vari‐
	       able) is set, boot first arranges for fossil to be able to con‐
	       tact the named venti(8) server.	The variable's value can  take
	       the following forms:

		      the  file	 should be a venti partition with a configura‐
		      tion stored on it using venti/conf  (see	venti-fmt(8)).
		      Boot will start a loopback IP interface on and
		      start venti announcing on tcp!127.1!17034 for venti ser‐
		      vice  and tcp!127.1!8000 for web service, using the con‐
		      figuration stored in that partition.

	       /dev/sdC0/arenas tcp!*!17034
		      same as the last but specify an alternate venti  service
		      address.	 In this example, using * will announce on all
		      available IP interfaces  (even  ones  configured	later)
		      rather  than  just  the  loopback	 device.  The loopback
		      interface is still configured.

	       /dev/sdC0/arenas tcp!*!17034 tcp!*!80
		      same as the last but specify alternate venti service and
		      web  addresses.  The loopback interface is still config‐

	       tcp!!17034 [ args ]
		      the network address of a venti server running on a sepa‐
		      rate machine.  Boot will configure the IP stack by pass‐
		      ing args, if any, to ipconfig(8).

	       Fossil is invoked as

		      /boot/fossil -f partition -c 'srv -A fboot' -c 'srv -p fscons'

	       and boot then renames to so fossil.conf should not use the  srv
	       command to create nor

	       If  the	disk  is  not  a  fossil(4)  partition,	 boot  invokes
	       /boot/kfs.  A variety of programs, like 9660srv	and  dossrv(4)
	       masquerade  as  kfs  to allow booting from alternate media for‐
	       mats, so as long as the disk is not a fossil disk, no check  is
	       made  that the disk is in fact a kfs disk.  The args are passed
	       to kfs(4).

	       For the tcp method, 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.

       On  PCs,	 the  default  arguments  to  boot  are	 constructed using the
       bootargs variable in plan9.ini(8).

       Start kfs(4) with extra disk buffers:

	      bootargs=local!#S/sdC0/fs -B 4096

       Use an IP stack on  an  alternate  ethernet  interface  with  a	static
       address and fixed file server and authentication server addresses.

	      bootargs=tcp -g ether /net/ether1 \

       (The  bootargs  line  is split only for presentation; it is one line in
       the file.)



       root(3), factotum(4), dhcpd(8), init(8)

       The use of bootargs in general is odd.  The configuration specification
       for fossil and venti servers is particularly odd, but it does cover the
       common cases well.

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