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diff --git a/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.md b/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.md new file mode 100644 index 0000000..c1b678d --- /dev/null +++ b/_posts/2015-03-28-reset-forgotten-password-on-luks-encrypted-ubuntu.md @@ -0,0 +1,51 @@ +--- +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. +--- + +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. + + + +By going down to the recovery mode option and hitting <kbd>e</kbd>, you can edit +the GRUB commands. By adding `init=/bin/bash` at the end of the line +beginning with `linux` 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 `cryptsetup luksOpen /dev/sda3 sda3_crypt`. + +Next, I mounted the freshly-unlocked disk with `mount -o rw /dev/sda3 /root`, +taking advantage of the pre-existing empty directory. From there, I used +`chroot` to run `passwd` 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. |