Linux/Security/Encrypted disk

Make a harddisk encrypted and password protected.

Use case

Unless hardware is not physically protected, it is mostly not necessary to take the overhead of encryption on every harddisk. Clear exceptions are external harddisks with sensitive information on them i.e. backup disks. If they leave the building, they might get lost or stolen.

Cryptsetup

Cryptsetup is a utility for setting up disk encryption using dm-crypt kernel module. It adds an extra step to mounting and unmounting in that a decrypted device needs to be created before mounting and removed after mounting.

Mount

# This creates /dev/mapper/backup
cryptsetup luksOpen /dev/sdb1 backup
# Now mount the decrypted device
 mount /dev/mapper/backup /mnt/backup

Unmount

umount /mnt/backup
cryptsetup luksClose backup

Install

Centos 6

yum install cryptsetup-luks

Centos 7

yum install cryptsetup

Encrypt a disk

WARNING: This procedure wipes data from the disk.

First find out which device is the disk that needs to be encrypted. If it is a USB disk, then plug it in.

fdisk -l

or

ls -l /dev/disk/by-id

Let us assume we found that the device is /dev/sdb.

Check if there are no partitions of /dev/sdb mounted at the moment. Else unmount them.

df

Create a partition partition on the device i.e. /dev/sdb1.

fdisk /dev/sdb

Format the partition as an encrypted.

cryptsetup luksFormat /dev/sdb1