Grub4dos Guide - Renaming grldr

If loading grldr via the Windows NT/2000/XP loader (ntldr), changing the grldr filename will result in Grub4dos failing to boot. Note from README_GRUB4DOS.txt - "...ntldr only loads the startup code of grldr (i.e., the leading 16 sectors of grldr), not the whole grldr file". The embedding settings in the startup code consequently scans for grldr in all available drives - if the file was renamed it will no longer be found. The following test was carried out on a dual boot system containing Windows Vista on (hd0,0) and Windows XP on (hd0,1). (hd0,1) was set as the active partition and mygrldr (renamed grldr) was loaded via C:\mygrldr="Grub4Dos" entry in boot.ini. This resulted in the following output -

It is possible to change the embedded setting to search for a different file by using the grubinst/grubutil tool. The procedure is outlined in README_GRUB4DOS.txt -

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***                      How to rename grldr                               ***
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grldr and grldr.mbr use internal boot file name to decide which file to load,
so if you want to change the name, you must also change the embeded setting.
You can do this with the help of grubinst, which can be downloaded at:

http://download.gna.org/grubutil/

grubinst can generate customized grldr.mbr:

	grubinst -o -b=mygrldr C:\mygrldr.mbr

grubinst can also edit existing grldr/grldr.mbr:

	grubinst -e -b=mygrldr C:\mygrldr

	grubinst -e -b=mygrldr C:\mygrldr.mbr

In this case, you must use a grubinst that is compatible with the version of
grub4dos, otherwise the edit will fail.

So, in order to load mygrldr instead of grldr, you can use one of the
following methods:

1. Use customized grldr.mbr to load mygrldr. In this case, you need to change
the embeded boot file name in grldr.mbr. The name of grldr.mbr can be changed
at will.

2. Use mygrldr directly. In this case, you need to change the embeded boot
file name in mygrldr to match its new name.

Notice: The boot file name must conform to the 8.3 naming convention.

Download the latest version of grubinst/grubutil (see here).

Copy grldr to C:\ drive and rename as C:\mygrldr

Open a command prompt and run the command grubinst -o -b=mygrldr C:\grldr.mbr - where -b=mygrldr will replace the embedded reference to grldr with mygrldr in the created file C:\grldr.mbr. Note - you can use any name for the file C:\grldr.mbr, however make sure you use the 8.3 naming convention.

Now load C:\grldr.mbr from Windows NT/2K/XP by adding C:\grldr.mbr="Grub4Dos" to your boot.ini file.

Alternatively, grubinst/grubutil can be used to edit an existing grldr and/or grldr.mbr file. This will require a compatible version of grubinst.

Copy grldr.mbr to C:\ drive and rename this file if required (making sure that you use the 8.3 naming convention). Run the command grubinst -e -b=mygrldr C:\grldr.mbr to replace the embedded reference to grldr with mygrldr. Now add entry C:\grldr.mbr="Grub4Dos" to boot.ini

Alternatively, copy grldr to C:\ drive and rename the file to mygrldr. Run the command grubinst -e -b=mygrldr C:\mygrldr to replace the embedded reference to grldr with mygrldr. Now add entry C:\mygrldr="Grub4Dos" in boot.ini

Unfortunately, at the time of testing, the latest version of grubinst (grubinst-1.1-bin-w32-2008-01-01) is not compatible with Grub4dos build 2009-02-05. Running command grubinst -e -b=mygrldr C:\grldr.mbr results in grubinst: Invalid input file error and grubinst -e -b=mygrldr C:\grldr results in grubinst: Version number mismatched (old=4 new=2) error.