mknbi-dos(8)

NAME

mknbi-dos - MaKe NetBoot Image for DOS

SYNOPSIS

mknbi-dos [OPTIONS] [<ramdisk> [<output file>]]

DESCRIPTION

mknbi-dos is a program to convert a MS-DOS or OpenDOS boot disk image into a file suitable for loading by diskless systems using a Boot-Rom.

OPTIONS

-b, --batch-sys SYS: Lets mknbi-dos operate in batch mode. It will look up the given system name in a database file and generate a netbootable image according to the parameters given in the database entry. If this option is not given, mknbi-dos will operate according to the other command line options. If giving any other options in addition to -b or --batch-sys, the parameters found in the database will override those processed from the command line.

-c, --simulate-hard-disk: Let the ram disk get mounted as a virtual hard disk instead of a floppy drive. Only floppy drives can be removed lateron, but a hard disk image can have a user selectable size.

-C, --config-file FILE: Specifies a configuration file.

-f, --skip-check: Disable certain validity checks when creating the ramdisk image. Normally mknbi-dos checks whether a ramdisk image has been created using a DOS system which is compatible with MS-DOS version 5.0 or higher or OpenDOS (though these checks are by no means complete). If you want to boot another DOS-compatible system like DR-DOS and mknbi-dos complains about an invalid ramdisk image, try using this option. But note that the DOS you want to boot has to support the RPL functionality of interrupt 2Fh. FreeDOS, the free DOS clone, for example, does not work with mknbi-dos for this reason.

-h, --help: Print short usage information.

-n, --no-hard-disk: When the ramdisk is simulating a floppy disk drive, this switch will disable hard disk accesses. This is necessary if the client should use a network file system as drive C:, which is only possible if there are no hard disks found by DOS.

-N, --netboot-dir DIR: Specifies the path of the main netboot directory.

-o, --outfile FILE: Pathname of output file, which is lateron loaded by the Boot-Rom via tftp.

-r, --ramdisk-image DIR|FILE: Pathname of ramdisk image. This can either be a file, a floppy device or a directory. If it's a directory, mknbi-dos will treat all files in that directory as MS-DOS files and will create a ramdisk image with a DOS filesystem and a simple boot sector in it. The directory has to contain at least the files IO.SYS, MSDOS.SYS and COMMAND.COM. Alternatively, it can also contain the corresponding files for IBM-DOS or OpenDOS.

-s, --ramdisk-size SIZE: Size of ramdisk in kB, which can not be smaller than that of the ramdisk image. If this option is missing, the size is determined from the size of the ramdisk image, if that image is a file. If it's a directory and this option is missing, the ramdisk size defaults to 1.44 MB. This option can be used with or without the -c option. However, when it is used without -c then the specified ramdisk size has to be one of 320, 360, 720, 1200, 1440 or 2880. Otherwise, any arbitrary ramdisk size can be selected.

-v, --version: Print version information.

-x, --verbose: Increase verbosity level.

RAMDISK SIZE

The actual size of the ramdisk is determined by several parameters. When the ramdisk is going to simulate a floppy drive, only the standard floppy sizes are available: 320, 360, 720, 1200, 1440 or 2880 kB. If the -s or --ramdisk-size options are not used, the actual ramdisk size will be identical to that of the floppy used for generating the ramdisk image, or 1440 kB if a UNIX directory is used. However, if the -s or --ramdisk-size switches are used, the value given has to exactly match the size of the source floppy image, or it can specify any value out of the standard floppy sizes as mentioned above when using a UNIX directory.

When the ramdisk is going to simulate a hard drive by using the -c or --simulate-hard-disk switch, the ramdisk size is determined by the size of the source floppy, or 1440 kB when using a UNIX directory as source. If using the -s or --ramdisk-size options the ramdisk size will be determined by the option argument, no matter what size the source floppy or UNIX directory has. The argument to the -s or --ramdisk-size option can have any value larger than 360 and is not restricted to the standard floppy values mentioned above. The maximum value is 16000.

When using a UNIX directory as the ramdisk image source, it's contents has to fit into the size as determined above. If the contents is larger, an error will be produced. However, due to internal restrictions the maximum amount of actual data on the source image or in the UNIX directory is limited to around 8 MB. This means that even though the ramdisk can have a maximum size of about 16 MB it can only be preset with data of about half this size.

MEMORY MANAGEMENT

The bootrom loads the image file created by mknbi-dos so that the ramdisk image is placed at the start of the extended memory on the client. When DOS starts, this memory area is not protected in any way against clobbering by client programs. But if the ramdisk driver finds that a XMS driver like HIMEM.SYS gets loaded, it will use it to allocate a XMS memory block to protect the ramdisk. Unfortunately, HIMEM.SYS, starting with version 3.10, does a check of extended memory which destroys the ramdisk image. You can use either a version of HIMEM.SYS prior to 3.10, or use the command line option /TESTMEM:OFF. When booting OpenDOS you have to load HIMEM.SYS before starting EMM386.EXE even though the documentation and the screen messages say that the HIMEM.SYS functionality is incorporated within EMM386.EXE. Unfortunately, when loading EMM386.EXE alone the ramdisk image gets corrupted for some reason. This can only be prevented when explicitely using HIMEM.SYS with OpenDOS.

To remove a ramdisk you can use the program rmrd.com which not only restores access to the physical drive which has been replaced by the ramdisk, but also frees all memory (including extended memory) used by the ramdisk image. However, a ramdisk can only be removed, if it is simulating a floppy disk drive (see option -c above). In a standard installation rmrd.com can be found in the directory /usr/lib/netboot/utils.

DATABASE FILE

mknbi-dos does not use any sections in the configuration file except the [general] section. However, for easier maintenance of different client configurations the database file can be used. The entries have to be preceded by a [<system name>:mknbi-dos] tag and can contain the following parameters:

outfile: Specifies the name of the output file

ramdisk-image: Specifies the name of the ramdisk image file or directory

ramdisk-size: Specifies the size of the ramdisk. This parameter works like the -s or --ramdisk-size command line arguments. The ramdisk size gets therefore determined in the same way as described above.

skip-check: This boolean parameter specifies wether to skip certain compatibility checks.

no-hard-disk: Boolean parameter which specifies if to allow hard disk accesses in the client or not.

simulate-hd: This boolean parameter allows the ramdisk to simulate a hard disk in the client.

BUGS

None known yet.

AUTHOR

mknbi-dos was written by Gero Kuhlmann <[email protected]>.