Ubuntu – How to create a file and mount it as a filesystem

You can use cryptmount to encrypt a filesystem, also if the filesystem is on a file.

The cryptmount manual page has a very simple and detailed explanation that I report (modified) here, and it do mention explicitly a file based filesystem.

• Step 1
  Add an entry in /etc/cryptmount/cmtab, as follows:

  mycrypt {
      dev=/media/data/mycrypt dir=/home/enzotib/mycrypt
      fstype=ext4 mountoptions=defaults cipher=twofish
      keyfile=/etc/cryptmount/mycrypt.key
      keyformat=builtin
  }
  

  where /media/data/mycrypt is the support file created by dd and /home/enzotib/mycrypt is the desired mountpoint.

• Step 2
  Generate a secret decryption key

  sudo cryptmount --generate-key 32 mycrypt
  

• Step 3
  Execute the following command

  sudo cryptmount --prepare mycrypt
  

  you will then be asked for the password used when setting up the key

• Step 4
  Create the filesystem

  sudo mkfs.ext4 /dev/mapper/mycrypt
  

• Step 5
  Execute

  sudo cryptmount --release mycrypt
  

• Step 6
  Now mount the filesystem

  mkdir /home/enzotib/mycrypt
  cryptmount -m mycrypt
  

  then unmount it

  cryptmount -u mycrypt
  

Also, if you need to crypt a directory, encfs may be worth to take into consideration.

Can you check the contents of /etc/fstab file ?

As its a very important file, backup it first.

sudo cp /etc/fstab /etc/fstab.bak

Instead of doing it on command line, do it using GUI tools please check this

http://www.webupd8.org/2011/11/how-to-mount-partitions-automatically.html

Note: Its a very important file. Please double check before doing any changes.

Update : Looks like you are not able to change settings with pysdm due to some bug in it - "No matter what I do with pysdm - Mount file system in read-only mode, still remains checked."

This can be fixed by manually editing /etc/fstab file . Changed

/dev/sda1                                  /media/sda1  ntfs  nls=iso8859-1,ro,umask=000,user  0  0  

to

/dev/sda1                                  /media/sda1  ntfs  nls=iso8859-1,rw,umask=000,user  0  0  

or even

/dev/sda1                                  /media/sda1  ntfs  nls=iso8859-1,umask=000,user  0  0  

and rebooted the system.