Tuesday 25 February 2020

E2B v1.B9j Beta available + grub4dos bug discovered

This version fixes the issue where Make_E2B_USB_Drive.cmd did not make a CONTIG.ISO file when requested.

It also now searches on Partition 3 for partition image files which have no file extension.

Ptn1: \_ISO\WINDOWS\WIN10\Win10 x64.imgPTN23    (FAT32 boot files)
Ptn3: \_ISO\WINDOWS\WIN10\Win10 x64    (NTFS >4GB INSTALL.WIM)

The Win10 x64 file (which has no extension) can either be in the root of the volume or in \_ISO or in the same path as the .imgPTN file. The file name should not have any dot in it or else it will be treated as having an extension.

This means the .imgPTN23 file can be the FAT32 boot partition and the file with no extension can be the NTFS volume containing your large install.wim file. You can secure boot and install >4GB install.wim files in this way. Instructions are on the agFM E2B page here.

Grub4dos bug discovered!

For a few years now, grub4dos was capable of using non-contiguous files when using the 'map' command with an ISO file, e.g.:

map /_ISO/ANTIVIRUS/krd.iso (0xff)
map --hook
chainloader (0xff)

would map the ISO as a (cd) device and boot from it.

I normally always run WinContig to make all the files on my USB drive contiguous, but the other day I noticed that grub4dos could not boot from the agFM ISO file which was on the second FAT32 partition because the ISO file was fragmented.

I checked previous versions of grub4dos and found that the bug had been introduced in the October 2019 version last year:

2019-08-09 OK
2019-09-09 OK    (E2B v1.B6)
2019-10-28 FAIL (E2B v1.B7)
2019-12-30 FAIL
2020-01-28 FAIL
If the ISO was loaded into memory, it seems to work, however the map command seems to actually work, but the chainloader command does not, so the typical command line of:

map /_ISO/ANTIVIRUS/krd.iso (0xff) || map --mem /_ISO/ANTIVIRUS/krd.iso (0xff)

does not actually run the --mem command.

Hopefully the developers can fix the problem soon and I can use the fixed version in the next version of E2B. In the meanwhile, if you get grub4dos errors when booting ISO files, make sure the file is contiguous!

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