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I have a lot of OneDrive storage and want to back up my files, but rather than putting them directly in the OneDrive folder, I'd rather put them in a TrueCrypt volume for security reasons. However, there is a limit on how large each file can be separately (2 GB). How can I split the TrueCrypt volume into smaller files? Is there any alternative to TrueCrypt that has this feature, or any program I can use to add this functionality?

Edit: I have 130 GB of storage, and I need to be able to automatically split this into 65 2GB volumes. This has to be in real-time, because recreating a 130GB volume is a time and resource consuming operation, especially on a laptop.

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6 Answers 6

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+50

TrueCrypt is not suited to such a large volume of data coupled to a 2GB file-size limit.

You should be looking at solutions for directly encrypting the OneDrive data. This way you will avoid the need to upload humongous files to OneDrive, just uploading the files that have changed.

Here are some products that do just that (in alphabetical order) :

Boxcryptor
Cloudfogger
nCryptedCloud
Viivo

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There is not a way for Truecrypt to do this. What you can do to make it a bit more effortless is to RAR the TrueCrypt volume into 2G pieces without using compression. This will make the process fairly quick.

WinRAR has a command line interface (rar.exe) which you could use to write a batch script to make the split and concatenation of the TrueCrypt volume. You could even use TrueCrypt's CLI options to automatically mount the volume after the concatenation.

Example commands:

# Split a file into 2G chunks and don't compress
rar.exe a truecrypt.rar truecrypt.tc -v2000m -m0
# Extract it
rar.exe e truecrypt.part1.rar

# Mount truecrypt volume
truecrypt.exe /q /v X:\
# Unmount truecrypt volume
truecrypt /q /dX 

Put these commands in two seperate batch files (umount and rar and extract and mount) and make sure the file names end with .bat. You can then run them by double-clicking.

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Since you want encryption for your cloud-stored files you could also use EncFS. It encrypts every file separately and stores it in a folder of your choice. I have succesfully used it together with OneDrive, Dropbox and Wuala.

With EncFS you get an unencrypted view of your files as a Drive (in Windows) or a FUSE mount (in Linux). The encryption/decryption is done transparently. Each of your files or folders results in an encrypted file or folder. (You can set that the file and folder names are also encrypted)

There is also a Windows version and several Android versions.

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  • Windows 10 not supported.
    – evilkos
    Mar 31, 2018 at 9:05
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split --bytes=2G INPUT_FILE OUTPUT_PREFIX

Edit: split is part of CNU CoreUtils for Windows.

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  • I'm running Windows. Mar 22, 2014 at 18:19
  • 1
    Welcome to superuser! At superuser we prefer answers that explain why you would do something as opposed to just the answer - that way if people have a similar problem they can modify your answer to fit their needs.
    – Jon
    Mar 22, 2014 at 19:30
  • I prefer not to have to split it into another file every time I mount/dismount the drive. It's going to be 130 GB in size. Is there any way for TrueCrypt to just read and write to the split files while it's working with the drive? Mar 23, 2014 at 13:03
  • I am not aware of such TrueCrypt functionality to run on multiple files.
    – andrej
    Mar 24, 2014 at 9:49
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I would try a combination of TrueCrypt and an archiver, which can mount a split archive as a virtual volume... Then you can Mount the virtual Volume from a split archive and put the Truecrypt File in there.

Some solutions for the archiver approach are discussed here:

Tool to mount a zip/rar/* archive as a Win drive and be able to read/write as a normal device?

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My solution to this would be to put the Encrypted Container INSIDE of a Virtual Hard Drive file.

Using the following:

1) VirtualBox (to create the Split VMDK) - https://www.virtualbox.org/

2) ImDisk (to mount the Split VMDK) - https://sourceforge.net/projects/imdisk-toolkit/

Instructions:

1) Download and install VirtualBox

2) Download and install ImDisk

3) Command Create Split VMDK: (change --filename and --size params as you see fit)

"C:\Program Files\Oracle\VirtualBox\VBoxManage" createmedium --filename D:\VirtualMachines\VMDK-SPLIT\VMs-VMDK-SPLIT.vmdk --format VMDK --size 123904 --variant fixed,Split2G

This will setup the disk in 2GB increments. Sorry, there is NO facility to change that to any other increment size. I checked.

4) Run the "Mount Image File" program on your desktop

Supply the:

Image File, Drive Letter

and then Check the box next to "Mount at Windows Startup"

5) When you go to mount this, IMDisk will ask you to Format the drive. Do that. After ImDisk formats it, it WILL NOT APPEAR in the drive list. Then Windows will ask you to format the drive again. DO THAT ALSO. That's when it WILL appear in the drive list.

You're all done. Now it will be permanently mounted!

So, you want some more control over the mounting? OR maybe you want to change the drive letter or completely stop it from auto mounting? Go to the registry at: HKEY_LOCAL_MACHINE\SOFTWARE\ImDisk

There you will find the registry entries for the drive letter

Here is my .reg file that I use to control that:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\ImDisk]
"MountPoint"=dword:00000000
"MountDir"=""
"ImMaxReg"=dword:00000000
"Im0FileName"="D:\VirtualMachines\VMDK-SPLIT\VMs-VMDK-SPLIT.vmdk"
"Im0MountPoint"="U:"
"Im0Param"=hex(b):00,00,00,00,01,00,00,00

To completely remove the mounting, just delete the registry entries in that IMDisk key.

I've done this already and found it to work pretty well.

Backups: Warning! Since the VMDK is a fixed size, it will not show a time/date change if the contents change inside of it. It will need to be backed up forcefully or with a content compare. I use SmartSync (www.smsync.com) and I tick the "File Contents" option. This forces the copy because it is comparing the content of the files.

Hope this works for everyone.
Please comment on your success or your problems with this solution.

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  • Sorry, there is NO facility to change that to any other increment size. I checked. Actually, there is. I checked. :-) You can generate the vmdk with an old version of vmdisk-vdiskmanager (as found on kb.vmware.com/s/article/1023856). I spent a few hours finding out about this, but basically you can e.g. do a vdiskmanager.exe -c -a ide -s 650MB -t 3 file.vmdk and then vdiskmanager.exe -x 1300MB file.vmdk and vdiskmanager.exe -x 1950MB file.vmdk etc. to start off with a 650MB file and grow/extend it with 650MB chunks. I learned though that 477 chunks/splits are the maximum.
    – SaeX
    Oct 6, 2019 at 18:39

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