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Emil Engler
Asked: 2018-11-03 16:07:44 +0800 CST

Change LUKS passphrase, which device?

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I have Ubuntu 18.04 installed on my UEFI machine. I want to change the passphrase of my luks encrypted volume. I already know the commands of how to do this. However I don't know which device I need to choose for changing the key ? The EFI parition which is smaller than 1GB or the root partition which takes the whole space of the system ?

encryption luks 18.04

1 Answers

  1. Usually you would have an unencrypted /boot and an extended partition (sda2 in this example) which have inside the LUKS partition. In this case is sda5

    $ lsblk # check also with lsblk -f
sda                       8:0    0 931,5G  0 disk  
├─sda1                    8:1    0   731M  0 part  /boot
├─sda2                    8:2    0     1K  0 part  
└─sda5                    8:5    0 930,8G  0 part  
  └─sda5_crypt          253:0    0 930,8G  0 crypt 
    ├─ubuntu--vg-root   253:1    0 929,8G  0 lvm   /
    └─ubuntu--vg-swap_1 253:2    0   976M  0 lvm   [SWAP]

    screenshot

    $ sudo cryptsetup isLuks -v /dev/sda5
Command successful.

    sudo cryptsetup luksDump /dev/sda5 for cipher name, mode, and more info.

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