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Hi George,
> At 07:04 PM 6/25/97 +0200, you wrote:
> How is the commandline option actually specified and used by
> the Etherboot's bootprom kernel? Are the commandline options
> specified in the bootptab file somewhere?
>
> So if you have a single bootimage file that embedds two
> distinct tagged boot image files, then the bootprom kernel
> will use the command line option provided and pick a correct
> tagged boot image from this "container file" and let the
> BIOS boot out of it? The "container file" would get pretty
> large i would think.
you are thinking far too complicated. In fact, I do not even
understand exactly what you were trying to do. Etherboot uses a rather
simple extension to the BOOTP format for passing command line
parameters. This is an excerpt from the README.VendorTags file:
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TAGS 192 thru 207
these tags define all of the valid boot images and override
any settings that are given with the "bf" bootfile option in
your "bootptab". It is allowed to leave gaps in the list.
This has an impact on how the `default' image will be
selected.
All entries are of the form
label:server:gateway:filename:passwd:flags:cmdline
For future extensibility, it is permitted to append an
arbitrary amount of other colon seperated entries as long as
the limit of 255 characters per tag is not exceeded.
Non-existant entries can be left empty. This means that the
default value for this particular entry will be used. Trailing
colons can be omitted.
label - this is the text string that is displayed to the
user. It can contain arbitrary characters, except
for a colon. Embedding arbitrary control
characters is not recommended, but you might be
able to include ANSI escape sequences (if enabled
in the ROM) for changing text attributes as long
as you restore the attributes at the end of the
string. It probably does not make very much sense
to leave this entry empty.
server - IP number of the TFTP server, where the image can
be found. This data has to be in decimal form
(e.g. 192.168.0.1); it is not permitted to use a
hostname. It is the responsibility of the "bootpd"
to look up hostnames. If this entry is omitted,
then the BOOTP server will be used for the TFTP
download.
gateway - use this IP gateway, when accessing the boot image
by TFTP. If no value is given, the BOOTP gateway
or alternatively the first entry in the list of
gateways "gw" is used.
filename- name of the boot image that has to be loaded by
TFTP. If this entry is omitted, then the machine
boots locally from disk. If enabled in the
BOOT-Prom, you can specify pseudo-filenames for
booting from a local blockdevice (floppy,
harddisk, ...); these filenames have to match the
pattern "/dev/[fh]d*". If the BOOT-Prom does not
have support for these pseudo-filenames, you can
still boot from blockdevices by storing an boot
image as generated by mknbi-blkdev under the name
of the desired blockdevice (symbolic links will
do).
passwd - MD5 message digest of the password. If this entry
is omitted, then no password is required for
loading this image. Support for passwords is
optional and might not be compiled into the ROM
image. For generating the MD5 message digest, you
can use freely available tools such as
"md5sum". C.f. the flags entry for controlling
the behavior of passwords.
flags - flags are used for controlling some aspects of how
the BOOT-Prom code behaves. All flags are a string
of decimal digits followed by a letter; multiple
flags can be concatenated. If this entry is
omitted, then a default value of "1i1p" is
assumed. Currently, these flags are defined:
0i - booting this image does not require a
password; the contents of the password
entry is ignored unless some other feature
(such as the flag "2p") requires it.
1i - booting this image requires a password. If
the password entry is omitted, or no
password support is available in the
BOOT-Prom, then this flag is ignored.
0p - the user cannot enter a command line for
passing parameters to the loaded image,
even if this feature has been enabled when
compiling the BOOT-Prom. N.B. this does not
affect the cmdline entry as described
below!
1p - the user does not get prompted for passing
parameters to the loaded image, but he can
explicitly request the prompt (e.g. by
pressing a modifier key while selecting an
image from the menu). If the password
entry is not omitted, then the password has
to be entered. Both parameter passing and
password validation can be disabled when
compiling the BOOT-Prom.
2p - the user always gets prompted for passing
parameters to the loaded image. If the
password entry is present and password
support has been enabled in the BOOT-Prom,
then the password has to be entered.
3p - the user always gets prompted for passing
parameters to the loaded image. No password
is required.
cmdline - the contents of this entry is appended to the end
of the command line that gets passed to the loaded
image. This feature is unaffected by the "p"
flags. Passing parameters currently does not make
sense for any operating system other than Linux
and is silently ignored for other operating
systems. As it is not legal to enter colons as
part of an entry, you have to escape them by
writing '~c' instead. This also means, that all
tilde characters have to be escaped by writing
'~~'. As some bootp daemons do not allow for
entering a backslash in a character string, the
escape sequence '~b' inserts a backslash
character. Currently, all other escape sequences
are undefined.
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If you need a more detailed description of this feature, feel free to
ask. As general rule, "etherboot"'s behavior is modelled to copy the
behavior that LILO exhibits.
Markus
--
Markus Gutschke Internet: markus@infoscape.com
Infoscape, Inc Phone: +1-415-537-3778
657 Mission Street, Suite 200
San Francisco, CA 94105
Disclaimer: The above message represents my personal opinion; It does
not constitute an offical statement by Infoscape!
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