ref: 6c7829092e71b407f16ff7229a19864439170761
dir: /sys/man/8/boot/
.TH BOOT 8 .SH NAME boot, bootrc \- connect to the root file server .SH SYNOPSIS .B /boot/boot [ .B -fkm ] [ .BI -u username ] [ .IB method ! device ] [ .I args ] .SH DESCRIPTION .I Boot is the first program run after a kernel has been loaded. It mounts .BR bootfs.paq , a compressed filesystem contained in .IR root (3), sets up the .IR rc (1) environment and executes .I bootrc passing on its arguments. .I Bootrc connects to the file server that will serve the root, performs any authentication needed to connect to that server, and executes the .IR init (8) program. Both .I boot and .I bootrc are started by the kernel, never run directly by the user. See .IR booting (8) for information about the process of loading the kernel (and .IR boot ) into memory. .PP Once loaded, the kernel initializes its data structures and devices. It sets the two environment variables .B /env/cputype and .B /env/terminal to describe the processor. It then binds a place-holder file server, .IR root (3), onto .B / and crafts an initial process whose sole function is to .IR exec (2) .BR /boot/boot , a binary which is compiled into .IR root (3). .PP 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 .IR boot . .PP On the PC, each line in the file .IR plan9.ini (8) of the form .IB name = value is passed to the boot program as an environment variable with the same name and value. The command line is .IP .B /boot/boot .IB method ! device .PP After .I boot passed its execution to .I bootrc, it must determine the fileserver to use and a .I method with which to connect to it. Typically .I device will name a local disk partition or ethernet interface. The complete list of methods is given below. .PP .I Bootrc 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. .I Bootrc will prompt for these. .PP Method and device are prompted for first. The prompt lists all valid methods, with the default in brackets, for example: .IP .EX bootargs is (tcp, il, local!device) [local!/dev/sdC0/fscache] .EE .PP A newline picks the default. Entering .B !rc breaks into the .IR rc (1) shell. Other possible responses are .IR method , .IB method ! device or .IB method ! device .IR args . .PP The other interactions depend on whether the system is a terminal or a CPU server. .SS Terminal A terminal must have a .I username set. If not specified with the .B user= .IR plan9.ini (8) parameter or the .B -u option, .I boot will prompt for one on the console: .IP .EX user: .EE .PP The user will also be prompted for a password to be used as an encryption key on each .IR attach (5): .IP .EX password: .EE .PP Once connected, .I boot mounts the root file system before .B / and makes the connection available as .B #s/boot for subsequent processes to .B mount (see .IR bind (2)). .I Boot completes by .IR exec (2)'ing .B /$cputype/init .BR -t . If the .B -m option is given it is also passed as an option to .IR init . If the environment variable .B init is set (via .IR plan9.ini (8)), it is used as an argument to .IR exec (2) instead. .PP If the .I bootfs.paq has been built with the cache file system, .IR cfs (4), the local disk partition .BI /dev/sd XX /cache (where .B XX is a unit specifier) exists, and the root file system is from a remote server, then .I bootrc will insert a user level cache process between the remote server and the local namespace that caches all remote accesses on the local partition. The .B -f flag commands .IR cfs (4) to reformat the cache partition. .SS CPU Servers The user owning devices and console processes on CPU servers and that user's domain and encryption key are read from NVRAM on all machines except PCs. PCs keep the information in the disk partition .BI /dev/sd XX /nvram. If a .B -k option is given or if no stored information is found .I boot will prompt for all three items and store them. .IP .EX password: authid: bootes authdom: research.bell-labs.com .EE .PP The key is used for mutual authentication of the server and its clients. The domain and id identify the owner of the key. .PP Once connected, .I boot behaves as on the terminal except for .IR exec (2)'ing .B /$cputype/init .BR -c . .SS 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. .TP 8 .BR tcp connect via Ethernet using the TCP protocol. The .I device and .I args are passed to .IR ipconfig (8) when configuring the IP stack. The .IR plan9.ini (8) variables .B fs and .BR auth override the file server and authentication servers obtained (if any) from DHCP during .IR ipconfig (8). .TP 8 .BR il the same as .B tcp but uses the IL protocol to connect to the fileserver. .TP 8 .BR local connect to the local file system. The .I device is a disk partition file holding a file system. .I Bootrc inspects the disk partition with .IR fstype (1) to determine the file system type and starts the appropriate server with .IR args . .RE .SH EXAMPLES On PCs, the default arguments to boot are constructed using the .B bootargs variable in .IR plan9.ini (8). .PP Start .IR cwfs (4) in config mode: .IP .EX bootargs=local!/dev/sdC0/fscache -c .EE .LP Use an IP stack on an alternate ethernet interface with a static address and fixed file server and authentication server addresses. .IP .EX fs=192.168.0.2 auth=192.168.0.3 bootargs=tcp!-g 192.168.0.1 ether /net/ether1 \e 192.168.0.50 255.255.255.0 .EE .LP (The .B bootargs line is split only for presentation; it is one line in the file.) .SH FILES .B #s/boot .br .B #//boot/boot .br .B #//boot/bootfs.paq .SH SOURCE .B /sys/src/9/boot .SH "SEE ALSO" .IR root (3), .IR dhcpd (8), .IR init (8) .SH BUGS The use of .B bootargs in general is odd. .SH HISTORY .I Boot first appeared in Plan 9 from Bell Labs. It was rewritten in .I rc for 9front (April, 2011).