Canon in D (Classical guitar) by Johann Pachelbel

How to unlock encrypted file system on Linux automatically

1. create a keyfile with random content

$ sudo su -
$ dd if=/dev/random of=/root/keyfile bs=1024 count=4

2. Add the file to LUKS

$ cryptsetyp luksAddKey /dev/sdb1 /root/keyfile

3. Edit /etc/crypttab

$ sdb1_crypt /dev/sdb1 /root/keyfile luks

4. Edit /etc/fstab

/dev/mapper/sdb1_crypt /media/Repository ext4 defaults 0 2

5. Reboot or Remount

Ternary operator(?:) in bash

Ternary operator is a short form of if/then/else

case $a in
    1) b=$c ;;
    *) b=$d ;;
esac

[[ $a=1 ]] && b=$c || b=$d
# At this case, 3rd part can be executed in case 2nd part fails

[[ $a=1 ]] && { b=$c; true; } || b=$d
# to avoid executing 3rd part by accident when 2nd part fails
## semicolon(;) is needed in {}