FAQ

Frequently Asked Questions (FAQ)

Q: What is the difference between device and volume mode?

In contrast to the volume mode, the device mode copies the whole USB device, including boot sector. So if you want to make a backup of a bootable USB device, or you have created a flash drive with more than one partition, you should use the device mode. The volume mode processes the first volume on an USB flash drive. Windows currently limits removable USB flash drives to only one volume. As long as the partition information on the flash drive doesn’t change and it is not a bootable device, it is ok to use the volume mode.

Q: The image file is slightly larger than the flash drive. Can I restore it anyway?

A: Generally it is not possible to restore a larger image file to a smaller device. Usually the partition on the flash drive (and so in the image) covers the whole flash drive. Even if your not using the full space on your flash drive, it might be possible that sectors at the end of the partition are in use to store data. Truncating this area will result in data loss. Also the partition info and file system info doesn’t match the real values, if you restore it to a smaller flash drive. The result is a corrupted file system that is not safe to use anymore. Nevertheless USB Image Tool offers the option to truncate oversize images in device mode(version 1.53). Beforehand you should manually resize the partition on the source flash drive with a partition tool of your choice (f.e. GParted Live CD) to fit on the target flash drive. After that you can do the backup of the source device and restore it to the target device with having the truncate option activated. Please note that you can’t do this on images you already created. Using this option without resizing the partition can result in partial data loss.

Q: I restored a smaller image file to a larger flash drive. Now it shows the smaller size. What can I do?

A: You have to extend the restored partition. You can do this with various partition tools. A freeware program is the Home Edition of Partition Wizard (http://partitionwizard.com/free-partition-manager.html).

Q: Why is the mode selection not accessible (grayed)?

A: Under Windows Vista the device mode requires administrative rights. Right-click the executable and select “Run as administrator”. This is obsolete with beginning version 1.60. USB Image Tool now always requires admin rights.

Q: Why doesn’t USB Image Tool expands/reduces the partition size?

A: Changing partitions and file systems is a difficult (and risky) task. By now USB Image Tool works regardless the used file system and partition type and I want to keep it this way. I did some research on this as well. Indeed there is a built-in API support in Windows for changing NTFS partition sizes. For FAT/FAT32, which is used on most of the flash drives, there is no such built-in support. Because of this USB Image Tool would have to perform all the file system and partition modifying tasks manually. On top of that FAT by architecture is not intended to grow or shrink in size. Basically it consists of a header, two allocation tables and the data sectors itself. To extend a FAT file system you would have to extend the allocation tables and move the data sectors that will be covered by the extended tables to unused space. As I did quite some parsing of the FAT file system for my DiskXS tool, I know this is a quite difficult and risky task, so I will leave it to tools specialized in this.

Q: How can I access the created image files without a physical USB device?

A: Various disk image software is capable of showing the content of an image. Personally I recommend WinImage (Shareware, www.winimage.com). Compressed image files (*.imz) are basically a zipfile with the raw image as a compressed file. You can rename and open them with any Zip-Utility to extract the raw image. Another helpful utility is OSFMount (http://www.osforensics.com).

Q: I restored an image of a bootable USB flash drive. Why does it not boot anymore?

A: Volume images do not contain the boot sector. A boot sector holds the boot loader, which makes the USB flash drive bootable. You can use the device mode to create an image of a bootable USB device.

Q: How can I create a backup of  a pendrive Linux or Linux partitions (ext3)?

A: To create an image of a pendrive Linux or a USB flash drive formatted with an unknown file system, you can use the device mode introduced with version 1.30.

Q: Can I write ISO files to a flash drive?

A: ISO files (images from CD/DVD) use a different file system (f.e. ISO9660, UDF) than image files for flash drives (f.e. FAT, FAT32)and usually can’t be used for flash drives. You can write them on a flash drive, but it won’t have the results, you probably expect. USB Image Tool doesn’t do any file system conversion, so most likely you won’t see the content of the ISO, when you write it on a flash drive.
There exist special ISO files with a hybrid bootloader (usually Linux LiveCDs), that can be used on a flash drive and a CD/DVD, but unless stated otherwise, ISO files won’t work on a flash drive. A more detailed discussion can be found here: http://reboot.pro/topic/16164-is-there-a-program-method-to-make-iso-image-from-bootable-usb/.

Q: Why is the image file so large, even if the USB flash drive isn’t full?

A: An image file represents the complete volume on a USB device, also its empty and unused sectors. However you can create a compressed image file, which can reduce the size of an image, depending on how good the whole image can be compressed. Neverheless, if the flash drive has once been filled completely with data, it may be still a large image, because the sectors could just be marked as unused, but still contain the data. This is how the common used FAT file system works. USB Image Tool has no knowledge of the file organisation on a volume and just knows about volumes and devices.

Q: What’s that 4 GiB limit for compressed images?

A: Originally the zip file format only used 32 Bit variables to store file size information. This limits the size, that can be stored correctly in this variables, to 4GiB. You might know this limitation from the FAT32 file system, which can’t create files larger than 4 GiB. For gzip files you can disable the size checks, making it possible to create gzipped files with archive contents larger than 4GiB. The gzip file will show the wrong uncompressed information, but it can be extracted correctly to it’s original size. The zip file format used is limited to 4GiB. Several extension have been made to store files larger than 4GiB into zip files, but most of the free available source code for zip compression/decompression can’t handle these extended zip files.

Feature Request List (FRL)

This features have been requested and taken into consideration:

  • command line utility (included with version 1.28)
  • Linux partition access (included with version 1.30)
  • checksum verification (included with version 1.42)
  • copy between USB flash drives (planned for next versions)
  • self-restoring executable (more difficult, maybe in next versions)

This features have been requested but won’t be implemented for now:

  • image encryption (zip encryption is either unsecure or propritary, software like TrueCrypt can be used to encrypt the image file or the drive itself )
  • image explorer (would require the implemetation of various file systems, specialized tools already exist)
  • grow/shrink partitions or images (see above and FAQ)
  • localization/translation (discarded for now)