Three  years  ago, I started using crypto containers for private data.
  Basically, I used this for mounting them:

    1   losetup /dev/loop0 "$IMG"
    2   cryptsetup luksOpen /dev/loop0 tresor
    3   mount /dev/mapper/tresor mount/

  Unmounting is done in a similar way:

    1   umount mount/
    2   cryptsetup luksClose tresor
    3   losetup -d /dev/loop0

  If you speak german, there's more verbose notes on that at [1].

  This works very well except for one thing: Your data is stored  in  an
  encrypted file of fixed size. So, from time to time, I had to increase
  that size from 50MB to 256MB to 1024MB...

  How about EncFS[2]?  Just tried it. It's simpler to  use  and  doesn't
  rely  on  files  with  fixed sizes. Looks good. I don't need "perfect"
  security so I don't care about  the  fact  that  people  can  see  the
  directory structure or the number of files (they can't see file names,
  of course).

  Why am I using encryption in the first place? I  want  to  protect  my
  data  if  my laptop gets stolen. That's it. Most probably, the average
  thief is not able to crack an EncFS. I bet he'd simply sell the laptop
  or wipe the hard drive so he can install Windows...

  ____________________

  1. gopher://uninformativ.de/0/txt/gnu-linux-notes/CryptSetup.txt

  2. https://wiki.archlinux.org/index.php/EncFS