"cryptsetup luksOpen /dev/sdb1 lin-bak", but it disappears after I reboot

[Todd And Margo Chester]

Hi All,

I can set up "/dev/mapper/lin-bak" with

    # cryptsetup luksOpen /dev/sdb1 lin-bak

but it disappears after I reboot. This messes up my
crypttab/fstab. Any idea what I am doing wrong?

Many thanks,
-T