up vote 40 down vote favorite
13

Having installed Ubuntu 11.10 with whole disk encryption and LVM, I need to provide a way for users to easily change LUKS passphrase.

Preferably, this should be done using GUI tools, thus, enabling novice users to perform this basic task.

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up vote 34 down vote

I am not familiar with gui tool but cryptsetup is the tool to interact with luks.

Basically AFAIK luks lets you add 8 passphrase slots and you can do that with:

sudo cryptsetup -y luksAddKey ENCRYPTED_PARTITION
sudo cryptsetup luksRemoveKey ENCRYPTED_PARTITION

where 0 is the slot number. I guess luks stores slots as 0,1,2 etc. But I recommend you to be very careful with luks as you may lock yourself out. Please refer to manual of cryptsetup. Also I recommend you to visit other distro IRC channel just to be extra safe before you proceed.

You may need to reboot the machine and try your new passsphrase as well before you remove the key.

cryptsetup

EDIT: Seems like gnome-disk-utility lets you change the passphrase.

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cryptsetup luksRemoveKey <partition> actually takes a keyfile as the last parameter. So if you want to input the passphrase, just give the device as parameter. cryptsetup will first prompt for "Enter LUKS passphrase to be deleted:" and then "Enter any remaining LUKS passphrase:" – user1338062 Apr 17 '13 at 9:30
    
You made my day. Thanks! – krlmlr Oct 10 '14 at 10:26
    
Avoid the gnome utility if your passphrase is very long, it may cut your input... – Thomas May 30 '15 at 20:51
    
@Thomas or whoever else is interested: at least 14 characters are not too long for the gnome disk utility. – KlaymenDK Apr 13 '16 at 13:52
up vote 17 down vote

Tested in ubuntu 14.04: Search for the "Disks" application

Select Device, select volume, Click cogs (more actions) -> "Change passphrase"

screenshot:

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Doesn't work with "long" passphrases... – Thomas May 30 '15 at 20:47
    
What actual application is this please? apt-get install ??? – shadowbq Oct 9 '15 at 13:16
    
FYI: gnome-disk-utility / apt-get install gnome-disk-utility && gnome-disks – shadowbq Oct 9 '15 at 13:23
1  
This is the built-in Disks application. No need to install anything. It works with fairly decent passwords. I haven't tried anything over 20 characters though. – Alain O'Dea Nov 26 '15 at 2:55
up vote 10 down vote 
cryptsetup luksChangeKey <target device> -S <target key slot number>

This will ask you first for a valid pass-phrase (in any enabled keyslot) then will prompt you fro the new passphrase in the target keyslot

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1  
In 12.04.5 I was asked for the new password twice. – Devin Lane Sep 19 '15 at 21:00

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