Xiaopan - boot from ISO on USB

A new tutorial has been added on how to add Xiaopan to a grub4dos multiboot USB drive here.

It dynamically finds and uses the UUID of the volume and can also use a 'persistent' data store.

The tutorial was written after a few hours of experimentation in response to a plea from reboot.pro forum member Hexley Darwin.

Using the SHIFT key to modify the behaviour of a grub4dos menu entry

If you have linux in your grub4dos menu.lst, you often need two entries, one for normal mode and one for safe mode so that you can boot on 'difficult' hardware.

This solution allows you to just have one menu entry but you can hold down SHIFT when you hit Enter to use safe mode parameters.

For this you need the bios utility on your drive (in this case in the root of the boot drive).You could also test for Ctrl or Alt and some other keys.

Note some lines are long and run over - use cut and paste!

title Run Linux\nPress SHIFT+ENTER for safe mode 

/bios int=0x16 eax=0x00000200 > (md)0x300+1
cat --skip=12 --length=2 (md)0x300+1 | set /a n=0x > nul 

set /a n=%n% & 0x03 > nul && if %n%>=1 echo SHIFT PRESSED! 

#LShift=01,RShift=02,CTRL=04,ALT=08,SCROLL=10,NUM=20,CAPS=40,INS=80 

#set /a n=%n% & 0x04 > nul && if %n%>=1 echo CTRL PRESSED! 

set sf=

if %n%>=1 set sf=acpi=off irqpoll noapic noapm nodma nomce nolapic nosmp 

kernel /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper %sf% splash 

initrd /casper/initrd.img



Bios Int 16 ah=2 reference here

NOTE: was...
/bios int=0x16 eax=0x00000200 > (md)0x300+1 && cat --skip=12 --length=2 (md)0x300+1 | set /a n=0x > nul

the 2nd half of the line is only executed if the BIOS returns non-zero. So && should not be used in this case.

WinContig version updated in RMPrepUSB

RMPrepUSB now uses a later version of WinContig to make all files on a USB drive contiguous. I have had it crash on several occasions when running on my USB FAT32 flash drives. The new version seems much more stable. 

Fix 'Error 60 - File not contiguous'!

You have probably come across this error message from grub4dos. It occurs when the file that it is trying to use is not contiguous.

To fix this you can run RMPrepUSB and select the USB drive and press Ctrl+F2 to run WinContig and defragment all files on the drive.

Making all file contiguous on a drive is not the same as defragmenting the drive. Defragmenting a drive shifts all the files to the beginning of the drive but often does not make all the files contiguous. WinContig does not shift the files if they are already contiguous and so WinContig is quicker and more effective than defragging the whole drive using a defrag utility.

Note: WinContig, Defraggler and other similar utilities usually need a contiguous run of free clusters on a drive so that they can copy the file into that contiguous space. Even after you run WinContig/Defraggler, you may not be able to copy over another large file and make it contiguous (even though there is enough free space on the drive) - see this post for details. Defraggler has an option to 'Defrag Free Space' which will fix this problem.

        This Defraggler map shows that the free clusters are not in one contiguous block. See here for more details.

To make a file contiguous,WinContig has to create a new file that is contiguous before it can delete the old non-contiguous file. Thus we need some contiguous free space on the drive that is the same size or larger than the size of the file we are trying to defragment. So for a 3GB file, we will need at least 3GB of contiguous free space on the same drive.

A file in a volume exists as a number of clusters (chunks of data). For example, a typical cluster size on an NTFS volume is 4K or 8 sectors. So a 10K file would occupy 3 clusters:

Cluster 1 = first 4K
Cluster 2 = 2nd 4K
Cluster 3 = 3rd 4K cluster (only first 2K of which has valid data)

These clusters can be anywhere within the volume. So they could be at cluster no 6,7 and 8 or they could be at cluster no. 3234, 44564 and 332!

A utility such as WinContig will rearrange the clusters within a file (if it can). So in the previous example, we might end up with the file consisting of cluster no.s  3234, 3235 and 3236 and so the file is contiguous and has sequential cluster numbers.

Recently, a user on reboot.pro had a problem. He had a 6GB VHD file on an 8GB NTFS-formatted USB drive. He ran WinContig but it would not make the file contiguous. Even copying the file to a freshly formatted 8GB NTFS drive did not work, the file was always non-contiguous.

It turns out that the reason for this is that when you format an NTFS volume, the Master File Table (MFT) is placed at the 3GB position within the volume (if the volume is over about 5GB). So on a freshly formatted 8GB volume, we have

(3GB of free space)
$MFT  (NTFS 'directory')
(4.7GB approx. of free space)

So we can see that there is no way we can store a 6GB sequential file with the MFT placed at the default 3GB position.

As the file is greater than 4GB, we cannot use a FAT32 filesystem (as FAT32 does not support files greater than 4GB).

You can see this if you use a utility such as Auslogics defrag tool which shows a map of the used clusters and what files occupy which areas of the disk.

Piriform's Defraggler is another good tool for displaying fragmented files and analyzing the file layout on a drive. It can also defragment individual files too (right-click in Explorer) and also offers to delete files in the Recycling Bin before defragging.

Alternatively, you can boot to grub4dos from the USB drive, go to the grub4dos shell (press c in the grub4dos menu) and then use the blocklist command to see how many fragments you have and where they are located - e.g.

So how can we make an 8GB USB flash drive containing a 6GB contiguous file?

Well, Wonko the Sane (from reboot.pro) came up with the idea of making a small NTFS volume and then re-sizing it (expand it), thus leaving the MFT in the same place (as it is not normally moved when resizing).

Here is how to make a bootable 8GB USB drive containing a 6GB contiguous file using the partitioning tool EaseUS Home Partition Master (EHPM):

1. Erase all ptns on the 8GB flash drive
2. Make a small 20MB NTFS PRIMARY ptn using EHPM - or RMPrepUSB if you want a special bootloader
3. Re-Size the ptn using EHPM to ALMOST the full drive capacity - e.g. 7.8GB
4. Now add a small 2nd FAT PRIMARY partition (this is to improve boot compatibility with some BIOSes - the ptn is not actually used)
5. Copy over your large 6GB file and check it is contiguous using WinContig.

If you have Vista or Win7/8, then you can use Disk Manager instead of EaseUS Home Partition Master.

The whole discussion can be found on reboot.pro here.

Having trouble still? See also my other blog article here.

Recommended: SanDisk Extreme Pro USB 3.1 (#ad)

Identify Unknown Devices in Device Manager

Came across a useful utility (UnknownDevices.exe  Dec 2012 version) by HalfDone which is intended to be run on a freshly-installed Windows system.

It looks at Device Manager (registry) entries and attempts to identify all the unknown devices which don't have drivers by using a database. It works on XP or later.
It also shows the Windows Product Key and lists a history of disk devices ever connected (inc. USB devices).
This is a useful addition for your toolbox!

As it relies on a database which needs to be updated as new hardware is released, you will need to get the latest version from the forum here.

fun with grub4dos batch files!

I have written a few new batch files which can be called by grub4dos - see here.

FindFullFileName.g4b - finds the first file matching a full filename
FindFileName.g4b - finds the first file matching a filename (without extension)
FindFileExt.g4b - finds the first file matching a file extension

title FindFileExt on mapped HDD Image
map  (bd)/harddisk.img (hd2)
map --hook
root (hd2,0)
# look for a file with a .com extension - param1=start folder   param2=extension
(bd)/grub/FindFileExt.g4b / .com
if not "%FILEPATH%"=="" echo FILE FOUND AT %FILEPATH%! 
if "%FILEPATH%"==""  echo No file with matching extension found!
pause
root
(more commands here)

Please download FindFile.zip to obtain these batch files.

Version 2.1.654 released as full version

The 'full release' version was getting a bit long in the tooth, so I have updated it with the latest version.
Changes can be read at http://www.rmprepusb.com/documents/release-2-0/version-history.
If you click on the Help (F1) button and click on the update box, the new version will be downloaded. You must then click on the downloaded file to install it manually.

Easy2Boot tutorial updated

I have included the AutoLinux code from Tutorial #96 into the Easy2Boot Tutorial #72.
I have also tested over 30 ISOs using the 'partnew' technique used in these tutorials and with 98% success; only the Trinity Rescue Disk ISO failed to work correctly.
Even DOS based ISOs just worked fine.
This allows you to just copy any ISO onto your Easy2Boot USB drive and try it. The menu is automatically made as the USB drive boots.

Automatic grub4dos Linux ISO boot menu entry

Tutorial 96 shows how to add a grub4dos menu entry that will automatically create a new dynamically-created grub4dos menu in a ramdrive and list all your linux ISO files. You can then choose one of them and boot from it.

Thus means that you should be able to quickly try any linux ISO that you fancy without needing to make a special menu entry for each one. Just download the ISO file and copy it to the folder on your grub4dos bootable drive. Then boot from the drive and chose the Linux ISO menu entry - all the ISO files in a folder will be listed (as shown below) and you should be able to boot from any one of the ISOs.

Even a BackTrack 5 iso will just work!

Tails you win! A new method for booting linux from an ISO file!

I recently came across a post on reboot.pro by cdob on how to map an ISO file to a partition using grub4dos. This technique has the advantage that it should work for most linux ISOs, even the ones that don't support booting from an ISO file!
It also can get around the problem of booting a version of linux from an NTFS boot drive, even if that linux does not understand or support the NTFS filesystem.
This means that even if your USB grub4dos boot drive is formatted as NTFS, you can boot nearly any linux ISO from it!

Cool!

I tried this out using a Tails linux ISO file (which at the time I could not find a way to boot from an ISO file) and it worked a treat.

You can even boot from Ophcrack ISO file AND access the rainbow tables (no need to extract the rainbow tables onto the USB boot drive!).

If you have a linux ISO that you cannot get booting as an ISO file from a grub4dos boot pen/hdd, try this technique!

See http://www.rmprepusb.com/tutorials/tails for details.

See also here for booting Tails 3.16 from a USB HDD.