You need to map it in the file /etc/crypttab.

You want to configure your /etc/crypttab file to look like this:
lin-bak     /dev/sdb1

On Sat, Jul 28, 2012 at 9:40 PM, Todd And Margo Chester <
[log in to unmask]> wrote:

> Hi All,
>
> Xfce 4.8
> Scientific Linux 6.2, 64 bit
>
> I have just encrypted my backup drive.  Is there anyway
> to get it into my fstab?
>
> Problem is rebooting removed the label I created in
> /dev/mapper with
>
>      # cryptsetup luksOpen /dev/sdb1 lin-bak
>
> and in fstab, I can add:
>   /dev/mapper/lin-bak  /lin-bak  ext4  defaults  1 0
>
> But "/dev/mapper/lin-bak" vanishes on me after a reboot.
>
> I can double click on the icon on my desktop and
> it will mount in "/media/lin-bak".  But this plays
> havoc on my scripts.  Gives me a long funny name
> in /dev/mapper too, which disappears when you
> dismount.
>
> Be nice to be able to get the drive into my fstab.
> If not, how do I mount it from the command line?
>
> If I try to mount directly, I get
>
>      # mount  /dev/sdb1  /lin-bak
>      mount: unknown filesystem type 'crypto_LUKS'
>
> Perplexed,
> -T
>