Microsoft Windows GPT support or "Excuse me! Which partition?"
Sunday, November 9. 2014
During a regular day I run a number of different computers. One day I wanted to take a copy of my Wall-E DVD and transfer it to iPad for later viewing. Since I sync that iPad to a particular Mac, I had to transfer the H.264 file of the movie there. As this was a one time thing and I happened to have a suitable USB-stick at my desk, I chose to go the old fashioned way. Copy the file to the stick and walk with the stick to the other machine. Except ... I couldn't copy the file to the USB stick. The stick was initialized with Mac OS X and contained a GUID partition table (or GPT). It completely refused to work with my Windows 7. What! Really?
The official word from Windows and GPT FAQ is:
Q: Can Windows 7, Windows Vista, and Windows Server 2008 read, write, and boot from GPT disks?
A: Yes, all versions can use GPT partitioned disks for data. Booting is only supported for 64-bit editions on UEFI-based systems.
Sorry, but I beg to differ. There seems to be some level of support, but ... not to the full extent. We're talking about Linux or OS X -level support here.
The stick looks like this during entire process:
# parted /dev/sde print
Model: JetFlash Transcend 8GB (scsi)
Disk /dev/sde: 8032MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:Number Start End Size File system Name Flags
1 20.5kB 210MB 210MB fat32 EFI System Partition boot
2 210MB 8031MB 7821MB fat32 Video
And this is how my Mac saw the situation:
$ mount
/dev/disk2s2 on /Volumes/VIDEO (msdos, local, nodev, nosuid, noowners)
This is what the Disk Manager of my Windows 7 said:
All looks good, except the OS failed to automatically assign a drive letter to the partition. No biggie, I can manually add one:
... except, I couldn't:
The error message of The system cannot find the file specified gave me an impression, that things aren't rolling my way.
At this point it wasn't about copying the file, but finding out what was going on. I had a Windows 8.1 right next to my Windows 7, so I plugged the USB into that one. This is what it saw:
But wait! There was something fishy about it. The drive capacity didn't match. To test it, I copied a file to the drive:
... and confirmed the Windows 8.1 error on a Linux:
# mount /dev/sde1 /mnt/usb/
# ls -l /mnt/usb/
total 1
-rwxr-xr-x. 1 root root 0 Oct 30 11:57 juttuhomma.txt
drwxr-xr-x. 2 root root 512 Oct 30 11:56 System Volume Information
Yep. The drive should be sde2, not 1! 
On a mac it was disk2s2, which would be equivalent. But a Windows 8.1 assigned the drive E: to 2nd partition! Nice. Apparently the support for GPT isn't that great.
And for those screaming "Piracy!" here's the pic:
According to Directive 2001/29/EC only "communication to the public" or "making available to the public" are limited. As I own a copy and am not publishing anything, ripping the encrypted MPEG-2 stream, converting it into H.264 and viewing it from my iPad is fully within my rights.
