19 replies to this topic

[apemax]

unetbootin is not recognizing my usb stick.the partition is formatted to FAT32. it is a crucial gizmo. any ideas?

[was_jaclaz]

unetbootin is not recognizing my usb stick.the partition is formatted to FAT32. it is a crucial gizmo. any ideas?

HOW (which tool/utility, under which OS, etc., etc.) did you partition/formatterd the stick?

jaclaz

[apemax]

i used gparted on linux ubuntu 9.04.

[was_jaclaz]

If you have a Windows based machine, try one of the "known to be working" methods:
http://www.msfn.org/...93-page-17.html

It is likely that your MBR has invalid data (or you don't have a MBR at all).

Alternatively, extract first sector (512 bytes) of the device (dd will do), compress it to a .zip or .7z archive and post it, I'll have a look at it and I may be able to tell you what happened/what is wrong with it.

jaclaz

[apemax]

ok i will try them. how do i extract the first sector?

[was_jaclaz]

ok i will try them. how do i extract the first sector?

Under Linux dd:

dd if=/dev/sda of=MBR.dat bs=512 count=1

make sure the USB stick is sda

Under Windows, most easy is HdHacker:
http://dimio.altervista.org/eng/
You want first sector of PhysicalDrive corresponding to the USB stick.

jaclaz

[apemax]

here is the boot sector.

Attached Files

•  BootSector_DriveF.zip   648bytes   770 downloads

[was_jaclaz]

That sector is NOT a MBR, it is a bootsector.

If it's the first sector of the device, the stick is formatted as "super-floppy", you need to format it "HD like".

In other words you have NOT a partition, you have an unpartitioned device formatted as FAT32.

jaclaz

[apemax]

sorry. this is the MBR sector.

Attached Files

•  MBR_HardDisk1.zip   540bytes   591 downloads

[was_jaclaz]

That MBR has:

• First entry/First partition FAT 16 CHS mapped (Type 06) NON Active
• Second entry/Third partition Hidden FAT16 CHS mapped (Type 16) NON Active
• Third entry/Second partition Hidden FAT32 CHS mapped (type 1B) Active

How you managed to get that mess you should know.

But it is rather obvious that having as active a hidden partition would not make it boot.

jaclaz

[apemax]

It can boot dam small linux,DSL.

[was_jaclaz]

It can boot dam small linux,DSL.

Good , but I don't get it if you are happy booting DSL, then keep booting it, and don't use Unetbootin.

It is you that came here whining about Unetbootin not recognising the stick.

I am telling you why.

You need at least one, possibly and hopefully the first, active, visible partition in order for Unetbootin to recognise the stick as a bootable device.

jaclaz

[apemax]

i did not whine. i just wanted to know why. what makes a patition active?

[was_jaclaz]

Basically in a MBR (first sector of a partitioned device such as a hard disk) there is an area (DATA) which holds the partition table.
This table is made of four entries, each 16 bytes long, that describe the partitions present on the disk, 1 entry=1 partition.
The maximum amount of partitions (Primary) on any given hard disk would be then four, if the clever guys who designed the PC booting process had not invented Extended partitions, that are containers in which more partitions (Logical Volumes) can be stored.
Thus the max allowed number of partitions is 3 Primary+1 Extended that can contain as many partitions as you wish.

To simplify, let's say that Extended partitions and Logical Volumes inside them are NOT bootable (which is not true, but needs some tricks ).
The first byte on each partition entry correspond to either Active (or Boot) or INactive Status, this, for historical reasons that would be long to explain, was coded as:
80=Active
00=INactive
There CANNOT be more than one Active partition.

Basically the PC BIOS loads first sector on booted from hard disk like device (the MBR or Master Boot record) and execute the CODE is in it.

This CODE normally inspects the DATA in the four partition entries and loads the first sector of the partition it can find marked as active (boot sector or PBR -Partition Boot Record).

The CODE in the PBR normally inspects the DATA in the PBR and loads the actual Operating System file(s).

This Active partition must normally be visible or UNhidden.

See here about partition types:
http://www.win.tue.n...on_types-1.html

as, if it is hidden, any of the steps involved in the described "normal" MBR+PBR+System File chain may fail, resulting in an unbotable system.

If you want to know more, here is a good place to start:
http://mirror.href.c.../mbr/index.html
and here are some tools you may want to play with:
http://www.boot-land...?showtopic=2959
http://www.boot-land...?showtopic=8734

As always, anything that comes from me is freely available according to my careware license :
http://home.graffiti...t/careware.html
which point #6 you already assertedly obliged to.



jaclaz

[apemax]

ok thanks for the help and all the information. that really clarified it.

[apemax]

I just realized something the first entry is the secure partition. is there any way of changing which partition is which entry?

[was_jaclaz]

I just realized something the first entry is the secure partition. is there any way of changing which partition is which entry?

Yes.
http://homepages.tes...no-answers.html

But you shouldn't "need" to....

Try simply unhiding the "Third entry/Second partition Hidden FAT32 CHS mapped (type 1B) Active".

What happens?

jaclaz

[apemax]

I did but it still won't recognized it. in the drop down box where you select what drive it is not there.

[was_jaclaz]

I did but it still won't recognized it. in the drop down box where you select what drive it is not there.

It is possible that unetbootin actually requires one single primary, active, partition, but I doubt it.


Are you sure that FIRST one is the "secure" partition?

That MBR has:

• First entry/First partition FAT 16 CHS mapped (Type 06) NON Active
• Second entry/Third partition Hidden FAT16 CHS mapped (Type 16) NON Active
• Third entry/Second partition Hidden FAT32 CHS mapped (type 1B) Active

Try attaching again your MBR, in the modified version that is still not working for you.
Try explaining to me what EACH of the three partition contain and WHICH one you want to make bootable.

jaclaz

[apemax]

sorry the second partition is the secure partition. the first entry was the one that came on the usb stick and is the one that i use to store my data. the second entry is the secure partition that also came on the stick. the third entry is the on that i want to make bootable and is also the one that DSL is on.

Attached Files

•  MBR_HardDisk1.zip   540bytes   532 downloads