boot – transfer control from the kernel to rc

/boot/boot [ args ]

Boot is the first program run after a kernel has been loaded. It sets up usb input devices if needed and creates a minimal namespace. It then exec(2)'s the plan9rc(8) script. 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). Boot completes by exec(2)'ing /boot/plan9rc.

The following information applies mostly to plan9rc(8) but has been left in this section of the manual for convenience to existing users. In general read "plan9rc" for "boot" in the section that follows and consult the plan9rc documentation for definitive reference.

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
authdom: research.bell–

The key is used for mutual authentication of the server and its clients. The domain and id identify the owner of the key.

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).
localconnect 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) variable) is set, boot first arranges for fossil to be able to contact the
named venti(8) server. The variable's value can take the following forms:
the file should be a venti partition with a configuration 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 service and tcp!127.1!8000 for web service, using the configuration 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 configured.
tcp!!17034 [ args ]
the network address of a venti server running on a separate machine. Boot will configure the IP stack by passing args, if any, to ipconfig(8).
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 formats, 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), plan9rc(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.