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A 300-byte database in the same format as the BOOTP message is used to
store the received packet. Once a BOOTP packet is broadcasted and received,
the database is marked as initialized, ending the first stage of the operation.
2. The client uses TFTP to obtain the image.
TFTP takes the information in the BOOTP packet (or uses a file name
specified in the command string or the environment variable BOOT_FILE and
gets the file from the server. TFTP accepts one parameter: the host address
concatenated to the file name of the remote file to be read.
Both BOOTP and TFTP use UDP (User Datagram Protocol) as the primary
transport mechanism to send datagrams to other application programs. TFTP
depends on UDP, which is an unreliable, connectionless Internet protocol.
Internet Booting Hierarchy
A complete description of Internet protocols is in Douglas Comer's Internetworking
with TCP/IP, Vol I, Principles, Protocols and Architecture, Second edition,
Prentice Hall.
The following list shows the priority of the different ways of Internet booting from
an initialized system:
1. Specify the file name as the named boot:
>>> boot -file filename ewa0
If the pathname includes a slash ( / ), it must be specified as a double slash
( // ). For example:
>>> boot -file //var//adm//ris//ris0.alpha//vmunix ewa0
Use this method only when using the -file option to specify the named boot or
to load the file name into the environment variable, BOOT_FILE.
2. Assign the file name to the environment variable BOOT_FILE.
This is the same method as the first one but the file name is taken from
BOOT_FILE. For example:
>>> set boot_file //var//adm//ris//ris0.alpha//vmunix
>>> boot ewa0
3. Assign the file name to the environment variable EWA0_INETFILE.
This method uses only the TFTP protocol. The BOOTP packet must already
be initialized. All other fields of the BOOTP packet must contain valid
information from a previous Internet boot.
4. Assign the file name to the environment variable EWA0_BOOTP_FILE.
boot
Console Commands 13–7
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Troubleshooting
