Posts Tagged ‘Recovery’

HowTo: Fix DVD/CD with Live filesystem (Packet/UDF) on Windows

The other day I found how easy it is to use a Live CD/DVD (where packet writing occurs when adding stuff) instead of a Mastered one (where all is kept to be written when you close the disk) on Windows.

It feels more like using a USB flash disk and should be more safe regarding losing data in the long run if you want to keep some file archive. In theory at least, since there are cases the live disk last write operation may fail and it may appear as an unreadable disk after one, making funny noises when you insert it and freezing for long time periods Windows Explorer when you try to access it.

However, the UDF filesystem that it uses keeps multiple VAT tables for the blocks written to the disk, which means it can be restored to the last workable state of the disk (you might still lose data from the last block I guess, but you’ll have access to the rest of the files you had written to the disk). For any files you find missing, you can try file recovery software with deep search option, like ISOBuster.

To restore such a disk back to working state, on Windows 10 you can right click the Start menu button and from the context (popup) menu shown, you can select to run PowerShell as Administrator. Then you can write CMD and press ENTER. The classic command-line shell (DOS syntax) will open up, where you should type-in chkdsk /f e: (replacing e: with the letter of the drive where the problematic disk has been inserted – can find that one easily from Windows Explorer / My Computer) and press ENTER again.

The disk should be detected as being of UDF format and the disk checking (chkdsk) command will check for a valid VAT on the last written block and if it can’t will try to revert the media to a previous state, before the corruption occurred by placing at the the end of the disk the last valid VAT.

Windows PowerShell
Copyright (C) Microsoft Corporation. All rights reserved.

PS C:\WINDOWS\system32> cmd
Microsoft Windows [Version 10.0.17134.165]
(c) 2018 Microsoft Corporation. Με επιφύλαξη κάθε νόμιμου δικαιώματος.

C:\WINDOWS\system32>chkdsk /f e:
The type of the file system is UDF.
Volume Μουσική is UDF version 2.01.

Chkdsk is running on media that does not support writes in place.
On such media chkdsk operation is limited to verifying the presence
of a valid VAT on the last written block and if necessary searching
for the last valid VAT and placing it at the end of the disk.
This could revert the media to a previous state before the corruption

Chkdsk could not find a valid VAT at the end of the volume.

CHKDSK is searching for a valid VAT …

And after some ages (stayed at 0% for some time and then took around a day progressing slowly on my machine for a DVD) you’ll hopefully see something like:

Search for VAT completed.
Chkdsk is copying last valid VAT at block 1722719 to the end of the
volume. This will revert the volume to its state at 01:13 on

Windows has made corrections to the file system.
No further action is required.

   4595200 KB total disk space.
    222240 KB available on disk.

      2048 bytes in each allocation unit.
   2297600 total allocation units on disk.
    111120 allocation units available on disk.

Then type exit followed by ENTER key twice to exit the command processor (cmd) and PowerShell. This will close the console window.

PS C:\WINDOWS\system32> exit

Enjoy your disk with its files again, hopefully all of them… Plus you’ll be able to add more files to the disk, which could have even been near to empty when the corruption had occurred. Note that when you’re finished and don’t want to write anymore files to the disk, you can right click it and close the session, so that it can be readable on more systems.

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