User guide

boot
boot — bootstrap the system
Initializes the processor, loads a program image from the specified boot device,
and transfers control to that image. If you do not specify a boot device, the
default boot device, defined by the value of the BOOTDEF_DEV environment
variable, is used.
You can specify a list of devices so that a bootstrap is attempted from each device
in order. When one of the devices boots successfully, control passes to that booted
image. Be sure to put network devices at the end of the list because network
bootstraps only terminate if a fatal error occurs or an image is successfully
loaded.
The flags option can pass additional information to the operating system about
the boot that you are requesting.
Use the -protocol option to specify either the DECNET MOP or the TCP/IP
BOOTP network bootstraps. Use the environment variable, EWA0_PROTOCOLS
to set the default protocol for a given port.
Note
Explicitly stating the boot flags or the boot device overrides the current
default value for the current boot request, but does not change the setting
of the corresponding environment variable.
TFTP and BOOTP
For the Internet environment, the console implements Boot Protocol (BOOTP) and
Trivial File Transfer Protocol (TFTP) clients to support network bootstrapping
and file transfers.
BOOTP is a standard protocol in the TCP/IP suite. It operates in the client-server
paradigm and requires only a single packet exchange. The machine that sends
the BOOTP request is the client; any machine that replies is the server. The first
packet sent requests a file transfer and establishes the connection between client
and server.
The packet specifies a file name and whether the file is to be read (transferred to
the client) or written (not currently supported). TFTP performs this operation.
Internet booting is a two-stage operation:
1. BOOTP provides the client with information needed to obtain an image.
13–6 Console Commands