I have the following scenario:

I want to automatically backup some data from my Laptop(Fedora Core 17) to a external encrypted(luks) hard disk. The disk can be opened by a key file, which lies on the also encrypted root partition of my laptop. The hard disk is attached to my docking station and therefore only "present" when I am at home (which is approximately 1/2 of the time the Laptop runs)

I have everything set up the way I want it with one exception.

I don't get a decent way to mount the hard disk automatically at boot if and only if it is present.

If I add it to crypttab and fstab without noauto it tries to mount it at boot and takes a lot(!) of time and error messages when it is not present. If I add noauto, well it does not mount automatically ;)

Is there a way to configure luks/crypttab to do the following:

• check whether the disk is present
• if yes: decrypt/mount
• if no: just don't