blob: b3154df76e3916dbcdf33219ad897e686c362500 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
|
---
title: How to Reset a Lost Password on a LUKS-Encrypted Disk in Ubuntu Linux
description: I recently needed to reset a lost password on an Ubuntu installation. But the LUKS encryption on the disk gave me some challenges. Here's what I did.
layout: post
category: writing
date: 2015-03-28 00:00:00
---
Here's the situation I recently found myself in:
* Ubuntu Linux 14.10
* Unknown password for user account
* Unknown (but set) root password (Ubuntu's philosophy is to use `sudo` for everything)
* LUKS encrypted filesystem (known passphrase)
* Physical access to the computer
<!--more-->
I needed to reset my account password. Normally, with physical access to a machine, all bets are off when it comes to security. I tried booting up the machine into [recovery mode](https://wiki.ubuntu.com/RecoveryMode) by holding down <kbd>shift</kbd> as soon as the BIOS had finished loading. But when I selected the "Drop to root shell" option, I was prompted to enter the unknown root password.
My second approach was to boot into single user mode by editing the GRUB command script.
<div class="text-center"><a href="/assets/images/ubuntu-grub.png"><img src="/assets/images/ubuntu-grub.png" alt="Ubuntu's GRUB menu"></a></div>
By going down to the recovery mode option and hitting <kbd>e</kbd>, you can edit the GRUB commands. By adding <code>init=/bin/bash</code> at the end of the line beginning with <code>linux</code> that specifies the boot image, you can specify an initial shell to use. Then I hit <kbd>F10</kbd> to boot.
After waiting for about 30 seconds or a minute, I saw a message that waiting for the root device (the locked disk) had timed out. I was then dumped into an [initramfs](https://wiki.ubuntu.com/Initramfs) shell. From there, I was able to unlock the disk by running <code>cryptsetup luksOpen /dev/sda3 sda3_crypt</code>.
Next, I mounted the freshly-unlocked disk with <code>mount -o rw /dev/sda3 /root</code>, taking advantage of the pre-existing empty directory. From there, I used <code>chroot</code> to run <code>passwd</code> in the OS.
{% highlight bash %}
$ chroot /root passwd
$ chroot /root passwd myUserName
{% endhighlight %}
By running these commands, I successfully reset both the root password as well as the password for my account. From there, I was able to restart the machine and boot normally.
*Is something here incorrect? Know of a better way to do it? Let me know [@bburwell](https://twitter.com/bburwell).*
|
