[mdlug] Compression and Archiving

[Raymond McLaughlin]

Ingles, Raymond wrote:
>> From: Drew
> 
>> Also, can an entire DVD be a squashfs filesystem? Or does it have to
>> be wrapped in an iso?
> 
> Based on my understanding, to write onto optical media needs a
> filesystem format specifically
> designed for that. So, either iso9660 or UDF.
> 
>  Sincerely,
> 
>  Ray Ingles                                                  (313)
> 227-2317

Just for grims, mostly, I have tinkered with writing other formats to
optical media, and found it can work. The command line cdrecord, or the
later wodim, will write any binary blob you feed it to the media without
complaint. You can do the same with K3b. It will give you stern
warnings, but let you proceed if you insist that you know what you are
doing.

I have written ext3 and ntfs filesystems to DVD in this manner.

Here is a procedure I used for creating a 4GB encrypted data DVD:

1. Using K3B create a standard ISO of the filesystem.

2. Using cp make a copy of this ISO. This creates a binary file exactly
the right size to contain the encrypted ISO.
  $ cp  data.iso crypt.iso

3. Link the second ISO to a loopback device, with encryption:
  $ losetup -e blowfish256 /dev/loop7 crypt.iso
  Password: ************************

4. Write data.iso to crypt.iso through the encrypted loop device.
  $ dd if=data.iso of=/dev/loop7

5. After writing completes, disconnect the loop device.
  $ losetup -d /dev/loop7

6. Test your encrypted ISO:
  $ mount -o loop,encryption=blowfish256 crypt.iso mnt
  Password: *************************

7. Once you are sure certain that the encrypted ISO works use K3B to
write it to your media. As mentioned K3B will object, but should allow
you to do it.

Of course such media require manual mounting and root or sudo-root
permissions, as do steps 3-7 above. But for grins at least, it can be done.