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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?

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Oops, it was indeed a typo! I always typed /dev/sd5 instead of /dev/sd5. Thanks Hamish for the hint. So I answer the question with the information from Andreas Härter (‌​nd_tricks) – Filbuntu Mar 5 '12 at 12:53
possible duplicate of How to change LUKS passphrase? – Gilles Jul 11 '12 at 23:09
up vote 14 down vote accepted

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

To add a new password, use luksAddKey:

sudo cryptsetup luksAddKey /dev/sda5

To remove an existing password, use luksRemoveKey:

sudo cryptsetup luksRemoveKey /dev/sda5

Cited from this blog. Thanks.

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does this imply you can have more than one password to unencrypt the disk? – bph Jan 18 at 16:05
It obviously implies it. The question is; can you have more than one? I'm taking a wild guess: Yes. – Rob Quist Jan 19 at 17:57
You can. I tested it out – bph Jan 25 at 22:31

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

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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).
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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
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