Wednesday, 5 December 2012

grub4dos and the blocklist command

It has always been there, but I have just found that the grub4dos blocklist command can be used to display the groups of contiguous sectors that make up a file. So you can use this command to check if an ISO file (for instance) is contiguous (and can therefore be directly mapped under grub4dos using map /xxx.iso (0xff)) or if it is not contiguous.
The file is 512 bytes long and thus occupies one sector on the disk. The file knoppix511.iso however is split into two contiguous sector 'runs', one starting at block 24856 (1425152 sectors long) and the other at 1450616 (976 sectors long).
WinContig is included in RMPrepUSB and can be used to make all files on the drive contiguous if you run into this problem.