Set of commands for creating OSX Journaled (Extended) Encrypted images. Attaching them. Detaching them. Attaching them on system boot.

hdiutil.sh

# Create a 10 megabytes, blank, AES 256 Encrypted, with password "mypassword",
# MacOS Journaled (Extended) image named "MyImage" when attached,
# and myimage.dmg as filename in the current directory.
#
echo -n "mypassword" | hdiutil create \
  -encryption AES-256  \
  -stdinpass           \
  -size 10m            \
  -fs "Journaled HFS+" \
  -volname MyImage     \
  ./myimage.dmg

# Attaches (Mounts) the ./myimage.dmg to /Volumes/MyImage
#
echo -n "mypassword" | hdiutil attach -stdinpass ./myimage.dmg

# Flags the /Volumes/MyImage volume as hidden so it doesn't show up on the Desktop.
#
chflags hidden /Volumes/MyImage

# Detaches (Unmounts) the MyImage Volume.
#
hdiutil detach /Volumes/MyImage

# Mounts the image on system boot.
#
crontab -e # (Opens Crontab Buffer) Add the following line:
@reboot /bin/bash -c 'echo -n "mypassword" | hdiutil attach -stdinpass /path/to/myimage.dmg'