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diff --git a/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.markdown b/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.markdown new file mode 100644 index 0000000..1c30045 --- /dev/null +++ b/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.markdown @@ -0,0 +1,34 @@ +--- +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 + +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="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. + + $ chroot /root passwd + $ chroot /root passwd myUserName + +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).* |