Member Avatar for riahc3

Hey

I want to make a VHDD (V.irtual H.ard D.rive D.isc) using the dd command and then encrypt it. I was told I had to do something with loop also to encrypt it but cant find anything. I dont want to experiment as dd is VERY powerful and can fuck up my drive. Thanks :)

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As explained, a loop device only makes a file look like a block device to the kernel — it doesn’t provide encryption. The usual, safe flow is: create a file to act as the VHDD, attach it to a loop device, put LUKS/dm-crypt on that loop device, open the encrypted mapping, make a filesystem inside the mapped device and mount it. Below is a compact, practical example (run as root or with sudo).

# create a 50MB container (sparse or preallocated)
truncate -s 50M vhdd.img

# attach a free loop device and show which /dev/loopX was used
losetup -f --show vhdd.img

# encrypt the loop device with LUKS (this will destroy any data on it)
cryptsetup luksFormat /dev/loop0

# open the LUKS container, creates /dev/mapper/securevhdd
cryptsetup open /dev/loop0 securevhdd

# create a filesystem on the mapped device and mount it
mkfs.ext4 /dev/mapper/securevhdd
mount /dev/mapper/securevhdd /mnt

# when finished: umount, close LUKS and detach loop
umount /mnt
cryptsetup close securevhdd
losetup -d /dev/loop0

Cautions and tips: verify the loop device path before running cryptsetup (use losetup -a or lsblk) so you don’t accidentally target a physical disk like /dev/sda. LUKS formatting destroys contents — to convert an existing unencrypted image, create a new encrypted container and copy files into it (mount both and use rsync). Remember that encrypted data looks random, so a sparse image will consume space as you write into it. Back up your LUKS header (with cryptsetup luksHeaderBackup) and store the passphrase/keyfile securely. Test the whole sequence in a VM if unsure.

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Member Avatar for John A

Well, the simplest way to make a blank image on your drive is to do something like this: dd if=/dev/zero of=filename.img bs=512 count=102400 That will create a 50 MB disk image with 102400 512-byte blocks (102400 blocks/2 blocks in a kB/1024 kB in a MB = 50 MB), and the image will be filled with zeros.

You can create an alternate version where the zeros are implied, but they aren't written to disk. Therefore, the disk image is sparse and will only use up the amount of space that data is actually occupying (as compared to the previous image, which will use 50 MB of disk space regardless of what's stored on it). dd of=filename.img bs=512 count=0 seek=102400 Finally, here's how you create a filesystem on it and store files. First, associate a loop device with your disk image. Usually /dev/loop0 is available for this (although if you've got some other disk images mounted, use the next available loop device). Note that you need root permissions for the following commands. losetup /dev/loop0 filename.img Now that you've got an associated loopback device, you can create your filesystem: mke2fs /dev/loop0 Finally, you can mount the filesystem: mount -t ext2 /dev/loop0 /mnt I'll leave the encryption up to you.

Member Avatar for riahc3

Well, the simplest way to make a blank image on your drive is to do something like this: dd if=/dev/zero of=filename.img bs=512 count=102400 That will create a 50 MB disk image with 102400 512-byte blocks (102400 blocks/2 blocks in a kB/1024 kB in a MB = 50 MB), and the image will be filled with zeros.

You can create an alternate version where the zeros are implied, but they aren't written to disk. Therefore, the disk image is sparse and will only use up the amount of space that data is actually occupying (as compared to the previous image, which will use 50 MB of disk space regardless of what's stored on it). dd of=filename.img bs=512 count=0 seek=102400 Finally, here's how you create a filesystem on it and store files. First, associate a loop device with your disk image. Usually /dev/loop0 is available for this (although if you've got some other disk images mounted, use the next available loop device). Note that you need root permissions for the following commands. losetup /dev/loop0 filename.img Now that you've got an associated loopback device, you can create your filesystem: mke2fs /dev/loop0 Finally, you can mount the filesystem: mount -t ext2 /dev/loop0 /mnt I'll leave the encryption up to you.

Thank you very much for the explanation :)

The problem is Ive already looked up encryption for more than a week and a half but havent found anything. And I thought that /dev/loop had something to do with encryption instead of mounting it (thats what I read)

Member Avatar for John A

Member Avatar for riahc3

Thank you again :)

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