Krdytkyu

I installed Ubuntu 11.10 with the alternate CD and encrypted the whole system (except boot) with the encrypted LVM. Everything works great as before, but I would like to change the password of the encrypted LVM. I tried to follow the Tips and Tricks of this article, but it does not work.
After typing:

sudo cryptsetup luksDump /dev/sda5

It says: "Device /dev/sd5 doesn't exist or access denied."
I thought the encrypted partition is /dev/sda5.
Any help how to change the password?

Here is the answer that worked for me, after Hamish helped me to realize my typo.

First, you need to find out which is the encrypted LVM partition, it may be sda3, but it can also be sda5, sdX2, ...:

cat /etc/crypttab

To add a new password, use luksAddKey:

sudo cryptsetup luksAddKey /dev/sda3

To remove an existing password, use luksRemoveKey:

sudo cryptsetup luksRemoveKey /dev/sda3

View currently used slots of the encrypted partition:

sudo cryptsetup luksDump /dev/sd3

Cited from this blog. Thanks.

Download "Disks" from Software Manager. Run it. Select your encrypted device partition. Click gear icon. Select "Change passphrase". That's it

Without thinking I set the passphrase to be really long, and it became a pain to type. I ended up using the following to change it to something more manageable.

sudo cryptsetup luksChangeKey /dev/sda5

To see the slots used:

sudo cryptsetup luksDump /dev/sda5

And to find out which partition to use

cat /etc/crypttab

And if it is listed by uuid, use

ls -l /dev/disk/by-uuid/{insert your uuid here}

Then use

sudo cryptsetup luksAddKey /dev/sda5

sudo cryptsetup luksRemoveKey /dev/sda5

or

sudo cryptsetup luksChangeKey /dev/sda5

and for faster reference (assuming only 1 entry in /etc/crypttab)

sudo cryptsetup luksAddKey /dev/disk/by-uuid/$(cat /etc/crypttab | sed -e "s|(.*) UUID=(.*) none.*|2|g")

sudo cryptsetup luksChangeKey /dev/disk/by-uuid/$(cat /etc/crypttab | sed -e "s|(.*) UUID=(.*) none.*|2|g")

The encrypted partition may well be using /dev/sda5 (note the a in sda5) and that is the device you probably need to use (unless that is just a typo in your question).

However the encrypted device itself will have another name - something like /dev/mapper/cryptroot. For the device name you could:

• look in the file /etc/crypttab - this will have both the partition and the mapper name in it, but only for permanent partitions


• run mount and see what the mapper name is - this is useful when you have plugged in an encrypted disk via USB. (Though I'm not sure how you then find the actual underlying device name).

I had issues locating partition name, so created this guide:

1. 
   

   Locate your LMV partition

   
   
   

   # install jq if you don't have it
   
   sudo apt-get install jq
   
   
   
   # find LVM partition
   
   LVMPART=$(lsblk -p --json | jq -r '.blockdevices | select(.children) | .children | select(.children) as $partition | .children | select(.type == "crypt") | $partition.name')
   
   
   
   # check if it was found
   
   echo $LVMPART
   
   
   
       # (optional)
   
       # if above output is empty, locate it in a tree view using this command
   
       lsblk -p
   
   
   
       # partition `/dev/some_name` should be the parent object of the one with TYPE of `crypt`, set it
   
       LVMPART=`/dev/some_name`
   
   

   
   


2. 
   

   Check LVM partition meta by dumping it

   
   
   

   sudo cryptsetup luksDump $LVMPART
   
   

   
   


3. 
   

   Add new key (you can have multiple keys)

   
   
   

   sudo cryptsetup luksAddKey $LVMPART
   
   

   
   


4. 
   

   After dumping it again, you should see multiple keys

   
   
   

   sudo cryptsetup luksDump $LVMPART
   
   

   
   


5. 
   

   Delete old key if desired

   
   
   

   sudo cryptsetup luksRemoveKey $LVMPART