Error during LUKS Header Backup ("Device /dev/sd... doesn't exist or access denied")

[r.pfeiffer222]

Hello everyone!

I am fairly new to using (x)ubuntu, so please excuse me if there is an obvious solution to this problem. However, I could not find the answer anywhere on the web, hence this post.

I am trying to install a LUKS-encrypted Xubuntu 14.04.2 Desktop (i386) distribution on my Acer Aspire One 533.

As mentioned above, I am a ubuntu-newbie, so I followed this tutorial exactly, and everything worked out exactly as it should (according to the tutorial) until I reach Step 9, where I am supposed to back up my LUKS-headers.

When I type in the terminal (according to the tutorial I linked to above)

root@xubuntu:/# cryptsetup luksHeaderBackup /dev/sda2 --header-backup-file /home/sda2backup.img

I receive the error message

Device /dev/sda2 doesn't exist or access denied.

I redid the whole process multiple times now, and everything works until I get to this point.

I will greatly appreciate any help.

Thank you in advance!

Cheers,
Ronald


Edit:

My System has the following specs:

Acer Aspire One 533-13Drr
Intel Atom N455
1 GB DDR3 RAM
250 GB HDD

The partitions I am trying to install are:

sda1	/boot	500 MB
sda2	/	20 GB
sda3	swap	2 GB
sda4	/home	the rest