I have an external HDD with two partitions on it. There's the primary partition and an additional partition I created called "Data" which is bitlocker encrypted (I created the Data partition on a Windows PC).
I've found two different ways of unlocking and mounting the Data partition on Ubuntu. I stumbled upon the first one myself accidentally, and the second one involving dislocker seems to be the standard approach you find by googling how to do this. I have several questions embedded here, so I bolded them.
Approach 1
I stumbled on the first approach by mistake, and I don't really understand it. It is to mount with the following commands:
sudo mkdir /media/WD_BLACK_DATA
sudo mount -t ntfs /dev/dm-3 /media/Data
The part I don't understand is the /dev/dm-3. Calling lsblk /dev/sdb gives the following output for this drive:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sdb 8:16 0 4.5T 0 disk
├─sdb1 8:17 0 4.2T 0 part /media/WD_BLACK_5TB
└─sdb2 8:18 0 377.2G 0 part
└─bitlk-77269abe-2988-4b8a-9ca9-a8508a975db7
252:3 0 377.2G 0 crypt /media/WD_BLACK_DATA
And calling lsblk without any arguments does not output /dev/dm-3 at all.
The Data partition is indicated by /dev/sdb2. Trying to mount the partition with sudo mount -t ntfs /dev/sdb2 /media/WD_BLACK_DATA gives an error. I can't find /dev/dm-3 anywhere, yet it works. I think the way I figured it out was Nautilus gave me an error at one point when I tried mounting it the wrong way, and the error message had a mention of /dev/dm-3, so I tried it out successfully. So one of my questions is: what is /dev/dm-3, and what query would I use to show me that /dev/dm-3 is the name of this partition? Why does mounting with /dev/sdb2 not work but using /dev/dm-3 does work? I can mount the non-encrypted drive just fine using sudo mount -t ntfs /dev/sdb1 /media/WD_BLACK_5TB
Approach 2: dislocker
Googling how to mount a bitlocker encrypted drive gives the this approach (e.g. this guide). Basically, I have to install the dislocker package, and do the following steps:
# Create a mount point for the dislocker file
sudo mkdir /media/bitlocker
Create a mount point for dislocker to mount the virtual filesystem
sudo mkdir /media/Data
is this just to decrypt the drive?
sudo dislocker -r -V /dev/sdb1 -u[PASSWORD] -- /media/bitlocker
mount the partition
sudo mount -r -o loop /media/bitlocker/dislocker-file /media/Data
In this approach, why are we having to create two mount points? What is the dislocker file? In mounting the partition, what is loop? When I run lsblk, there are many entries with loop in the name; example:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 4K 1 loop /snap/bare/5
loop1 7:1 0 313.1M 1 loop /snap/code/172
loop2 7:2 0 316.5M 1 loop /snap/code/173
loop3 7:3 0 572K 1 loop /snap/color-picker/26
All these loop entries are related to snap, but dislocker isn't related to snap, so what's actually happening here?
I can configure /etc/fstab using either of these approaches. For approach 1, it's /dev/dm-3 /media/WD_BLACK_DATA ntfs password=<password> 0 0
Approach 1 is way more convenient and straightforward (aside from figuring out that the name to use was /dev/dm-3), so why is that not the standard approach? And what advantages if any does using dislocker provide?
