To be specific, I want it to be impossible to boot up my linux computer without a certain sdhc card inserted. And I don't want the bios to boot from the sdhc card. Also, if the sdhc card is removed when the computer is on, I want it to do a full secure wipe of the main hard drive.. I have no idea where to start on this and I couldn't find anything on google except booting with a full linux image on the sdhc card, which I don't want. So the sdhc card would be the /boot partition. But how to only boot from my sdhc so that if someone else tries to use their own sdhc card to boot, it will deny access....
migrated from serverfault.com Jul 5 '13 at 3:37
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Just a few thoughts.
As mentioned by Kevin Soviero I would look into LUKS for the encryption and storing the keyfile on a external device. You can find information for instance at https://wiki.archlinux.org/index.php/Dm-crypt_with_LUKS
For the second part I would look into udev and create a rule that would call a script to wipe things when the card is removed.
You can test your setting by actually removing the SD card. Don't forget to make an exact copy of your hard disk beforehand.