2011-06-18 // Full disk encryption with Ubuntu (9.04 Jaunty or newer), LVM and LUKS

This article provides a step-by-step guide on how to install an Ubuntu Linux system with full disk encryption (new installation). However, you should take a relaxed day as topical newbie for further reading. You don't have to keep everything in mind but it is never an error to acquaint oneself with something new.

In this case, full disk encryption means:

• All non-boot data of the system will be encrypted (incl. temporary files and swap)
• Only a small boot partition remains unencrypted to store the boot loader and the kernel. The security of your data won't be affected by this.
• Automatic real-time, on-the-fly encryption incl. pre-boot authentication.

Additional key points:

• This how-to does not use the (IMHO inflexible) Alternate-CD crypto setup.
• There will be a separate /home partition within the encrypted volume, making backups and fresh installations easier.
• Despite the fact that there is more than one single encrypted partition, you only have to enter one single password during boot time. The Logical Volume Manager (LVM) is used to make this possible. LVM will be used as “crypto container”, containing the different partitions /, /home and swap.
• You don't loose any comfort – apart from the password question when the system boots, you don't have to expect any changes during daily usage. This is also true regarding kernel and/or distribution updates, there is nothing special to keep in mind. Therefore it is really worth it to tough it out.
• Suspend-to-disk (S4)/hibernation works (if it also would work on an unencrypted installation, for sure).
• Thanks to Logical Volume Manager (LVM), subsequent partitioning changes are possible.

Short summary to get an overview of the actions needed to be done:

1. Boot a live session plus install the needed software (LVM, LUKS/cryptsetup).
2. Subdivide the target device into two partitions:
   • small boot partition (~200MB are more than enough)
   • unformatted partition (remaining space)
3. Encrypt the unformatted partition, unlock it afterwards.
4. Creation of a LVM group on the unformatted, unlocked crypto partition, containing the root, home and swap partition.
5. Start of the graphical Ubuntu installation wizard, telling it to use the root, home and swap partition within the encrypted LVM group plus the small, unencrypted partition as /boot.
6. Do not reboot directly after the installation wizard finished its work. Change into the freshly installed system with chroot instead. This is needed to install the required software (LVM, LUKS/cryptsetup) on it (you won't be able to boot it otherwise).
7. Reboot.

If it's all Greek to you, don't be scared. It is no rocket science.

• A Ubuntu installation CD (not the Alternate-CD) to be able to start a live session: download
• Working Internet connection. You have to install some additional software packages during the live session (for which Internet connection is necessary). It is probably most convenient to connect your system to a Internet router or something similar to prevent needless configuration at the live session. If your network card does not work out-of-the-box, you may want to temporarily install a cheap Realtek NIC or something like that.

I provide a crypt-setup bash script, making the system installation faster and easier. The scripts prompts the user to enter the needed data (target device, partition sizes, key length etc.) and processes the installation as described at ”Manual installation” afterwards. This saves much typing and prevents errors. Using the script, a full disk encryption setup should only take a few minutes longer than a default installation.

1. Start the live session. Boot from the installation CD and start a live session (not the installer). The fitting menu item should be “Try Ubuntu” or something similar (the notation may vary a little bit, depending on the Ubuntu version and when/if a key was pressed). Please choose the language you are going to use on the installed system right from the start. This prevents problems regarding the keyboard layout and the password setup.¹⁾
2. Run the script. Open a terminal and run the following commands to download and start the script (copy and paste recommended):

   wget "http://blog.andreas-haerter.com/_export/code/2011/06/18/ubuntu-full-disk-encryption-lvm-luks.sh?codeblock=1" -O "/tmp/ubuntu-full-disk-encryption-lvm-luks.sh"
   chmod a+rx "/tmp/ubuntu-full-disk-encryption-lvm-luks.sh"
   sudo "/tmp/ubuntu-full-disk-encryption-lvm-luks.sh"

Boot from the installation CD and start a live session (not the installer). The fitting menu item should be “Try Ubuntu” or something similar (the notation may vary a little bit, depending on the Ubuntu version and when/if a key was pressed). Please choose the language you are going to use on the installed system right from the start. This prevents problems regarding the keyboard layout and the password setup.²⁾

Because the full disk encryption will be prepared by using a live session (which brings no more than what is absolutely necessary), you have to install some additional packages plus their dependencies for the running session (lvm2 and cryptsetup). Open a terminal and execute the following command:

sudo apt-get install lvm2 cryptsetup

You can't reboot for understandable reasons (→live session, your changes would be gone after a reboot). This is why you have to load a needed kernel module manually (provided by the packages you installed) using the termimal:

sudo modprobe dm-crypt

Now the current live session does provide everything you need to install the encrypted system.

You have to subdivide the target hard disk into two partitions. This will be done with GParted.³⁾ Start it via terminal (→ gksudo gparted) or by clicking “System→Administration→GParted”

The following partitions are needed:

• dev/sdX1, ext3, 200MB at the beginning
  You can use up to 17 chars for the description. I chose “boot (no crypt)”.
• dev/sdX2, unformatted, at least 8GB (the root, home and swap partitions need to find room).
  You can use up to 17 chars for the description. I chose “sys (lvm,crypt)”. Normally, you should simply use all remaining space (how it was done in the following).

You can close GParted after all operations were applied (→ green check mark).

sudo shred -vn 1 /dev/sdX1
sudo shred -vn 1 /dev/sdX2

The partition sdX2 will be prepared to act as crypto device by using the cryptsetup luksFormat command. This is also the moment to decide which encryption algorithm, chaining mode and initialization vector should be used. aes-xts-plain is recommended because it brings protection against so called “watermarking” and other known attacks plus encrypts your data securely by using AES:

sudo cryptsetup --cipher aes-xts-plain --key-size 512 --verify-passphrase luksFormat /dev/sdX2
[define the password. Attention: there will be no feedback like * or something similar]

After formatting, the crypto device needs a name and has to be unlocked to make it possible for the installer to access it. The device is accessible via /dev/mapper/<chosen name> if everything works. I chose the name lvm_crypt:⁴⁾

sudo cryptsetup luksOpen /dev/sdX2 lvm_crypt

The Logical Volume Manager (LVM) won't be used to connect multiple drives here. It is used to prevent the management of different keys respectively the need to type multiple passwords when booting the system. Because /home gets its own partition and swap is also encrypted, you normally would have to type a separate password for each partition. To bypass this annoyance, a LVM volume incl. LVM volume group will be generated within the opened crypto partition you created earlier by using the cryptsetup command. pvcreate is used to initialize the LVM volume, vgcreate creates the LVM volume group within the LVM volume:

sudo pvcreate /dev/mapper/lvm_crypt
sudo vgcreate ubuntu /dev/mapper/lvm_crypt

Now you are able to create the needed partitions within the LVM volume respectively the LVM volume group ubuntu. Swap should be ~1.3 times greater as your installed RAM (at least if you want a solid suspend-to-disk (S4)/hibernation). If space is rare (e.g. when using a SSD), you certainly want to use less. But opinions about a sane swap size differ as much as the ones about the size of the root partition. This is why you should look at the following values as an example (but they can be adopted without any problems). The PC I used to write this article got 4GB RAM (→ multiplied by 1.3 = 5200MB swap) and I created a 25GB root partition:

sudo lvcreate -L 5200M -n swap ubuntu
sudo lvcreate -L 25000M -n root ubuntu
sudo lvcreate -l 100%FREE -n home ubuntu 

If you need additional/other partitions, you can create them by using the same schema. If you have problems with the syntax, man lvcreate may be helpful.

You should format the created partitions to prevent problems with some versions of the graphical Ubuntu-installer ubiquity (during the graphical installation of the real system, the partitions will be formatted again. So don't worry if you want to choose another file system than EXT4: you can choose it there):

sudo mkswap /dev/mapper/ubuntu-swap
sudo mkfs.ext4 /dev/mapper/ubuntu-root
sudo mkfs.ext4 /dev/mapper/ubuntu-home

The needed preparations of the encrypted device are finished now. All needed partitions are existing and the installation of the real system can begin.

Start the graphical Ubuntu installation wizard by clicking the “Install Ubuntu <version>” icon on the desktop:

After choosing language, time zone etc. you have to choose “specify partitions manually” at the “Prepare disk space” window (the notation may vary a little bit, depending on the used Ubuntu version). There you have to assign the partitions you created before:⁵⁾

• /dev/sdX1
  • Boot partition
  • File system (“use as”): ext3 journaling file system (no ext4 to prevent compatibility issues)
  • Format the partition: yes
  • Mount point: /boot
• /dev/mapper/ubuntu-root
  • Root partition
  • File system (“use as”): ext4 journaling file system (or your own option)
  • Format the partition: yes
  • Mount point: /
• /dev/mapper/ubuntu-home
  • Home partition
  • File system (“use as”): ext4 journaling file system (or your own option)
  • Format the partition: yes
  • Mount point: /home

Complete the setup by following the instructions of the installation wizard. You may activate the “Log in automatically” option (without bad conscience) to prevent the need for typing an additional password before logging in. The encryption password should be enough in single-user environments. Do NOT reboot the system after the installer finished. There is still some work to do.

If you would reboot your system now, the installed system couldn't boot. It still needs the software to access the encrypted drive and has to prompt the user for the password. Therefore we use chroot to change into the freshly installed system to install the needed packages lvm2 und cryptsetup (Attention: all following commands have to be executed within the same terminal window. And don't forget to replace sdX1 with your own partition, e.g. sda1):

sudo mount /dev/mapper/ubuntu-root /mnt
sudo mount /dev/sdX1 /mnt/boot
sudo mount -o bind /dev /mnt/dev
sudo mount -t proc proc /mnt/proc
sudo mount -t sysfs sys /mnt/sys
sudo cp /etc/resolv.conf /mnt/etc/resolv.conf
sudo chroot /mnt /bin/bash
apt-get install cryptsetup lvm2

Now, you are almost done. Ubuntu was installed into a LVM group on a crypted drive and has the software necessary to decrypt the data. In order to ask the drive to decipher automatically when booting the system, you have to write a fitting UUID entry for the /dev/sdX2 partition into the /etc/crypttab file. The following command detects the UUID and writes the needed line into /etc/crypttab (don't forget to replace sdX2 with your own partition, e.g. sda2):

echo "lvm_crypt UUID=$(ls -la /dev/disk/by-uuid | grep $(basename /dev/sdX2) | cut -d ' ' -f 9) none luks" >> /etc/crypttab

The system has to inherit the /etc/crypttab changes now (you can ignore “cryptsetup: WARNING: invalid line in /etc/crypttab” and “Cannot find /lib/modules/[…]-generic” warnings):

update-initramfs -u -k all 

Done . You should be asked for the password when booting the system. Work with your securely encrypted system as usual. Simply close the chroot environment and reboot your computer:

exit
sudo reboot

• Change/add/remove passwords: LUKS is able to manage up to eight passwords at the same time. Each password will be stored in a so-called slot (0-7). The currently used slots of the encrypted partition can be printed out by using luksDump (don't forget to replace sdX2 with your own partition, e.g. sda2):

  sudo cryptsetup luksDump /dev/sdX2
  
  [...example output follows...]
  Key Slot 0: ENABLED
  	Iterations:         	xxxxxx
  	Salt:               	[...]
  	                      	[...]
  	Key material offset:	8
  	AF stripes:            	4000
  Key Slot 1: DISABLED
  Key Slot 2: DISABLED
  Key Slot 3: DISABLED
  Key Slot 4: DISABLED
  Key Slot 5: DISABLED
  Key Slot 6: DISABLED
  Key Slot 7: DISABLED

  To add a new password, use luksAddKey:

  sudo cryptsetup luksAddKey /dev/sdX2

  To remove an existing password, use luksRemoveKey:

  sudo cryptsetup luksRemoveKey /dev/sdX2

• Access an encrypted system from a Live CD: In the case of emergency, it may be useful to have access to the encrypted files of a system installed by using this manual (you need the password, for sure). Boot the Live CD and install the needed software:

  sudo apt-get install lvm2 cryptsetup
  sudo modprobe dm-crypt

  Open/decrypt the device (replace sda2 with your device if needed):

  sudo cryptsetup luksOpen /dev/sda2 lvm

  Activate the LVM to get /dev/ubuntu/home, /dev/ubuntu/root and /dev/ubuntu/swap:

  sudo pvscan
  sudo vgscan
  sudo lvscan
  sudo vgchange -a y

  Mount the root and home partition:

  sudo mkdir /mnt/root
  sudo mount /dev/ubuntu/root /mnt/root
  sudo mkdir /mnt/home
  sudo mount /dev/ubuntu/home /mnt/home

  Now you can access your home partition via /mnt/home, the root partition is located at /mnt/root. So you can copy or edit all of your data. If you don't have enough permissions to copy needed files, try it with a filemanager started with gksudo nautilus.

Enrcypt a system

• Artikel im Linux Magazin 2005/08: Geheime Niederschrift - Festplattenverschlüsselung mit DM-Crypt und Cryptsetup-LUKS: Technik und Anwendung
• Debuntu: How-To: encrypted partitions over LVM with LUKS
• System verschlüsseln
• Daten verschlüsseln
• Logical Volume Manager (LVM)
• Linux Unified Key Setup (LUKS)

Other

• Disk encryption theory
• Block cipher modes of operation
• Initialization vector
• Advanced Encryption Standard (AES)
• Universally Unique Identifier (UUID)
• Pre-boot authentication
• Was bringt EXT4?

Notice: this article was published on http://readm3.org/os/ubuntu/full-disk-encryption-lvm-luks first. I moved it to my blog for organizational reasons.

Comments

Johannes

No. 1 @ 2011/07/25 00:07

Vielen Dank für das tolle Script. Super Arbeit :)

Hier noch ein Hinweis für diejenigen, die wie ich nicht Ubuntu verwenden wollen. Sollte die Distribution Ubuntu-basiert sein (in meinem Falle Linux Mint 11, ich vermute die meisten Debian-Varianten sollten auch funktionieren), muss das Script geändert werden, da der Installer natürlich nicht im Script hinterlegt ist. Dadurch bricht das Script ab und ihr müsst neustarten und von vore anfangen. Sucht im Script nach der Zeile

ubiquity –desktop %k gtk_ui > /dev/null 2>&1 #command copied from the properties of the GNOME starter on the Live CD's Desktop

Ersetzt sie mit dem Befehl für den Installer eurer Distribution (zu finden über einen Rechtsklick auf das Symbol auf dem Desktop unter Eigenschaften), lasst aber natürlich das

/dev/null 2>&1

dahinter stehen. Und schon seid ihr dabei.

Grüße

» Reply

Merlin

No. 2 @ 2011/08/14 20:12

I followed the tutorial, combining it with manual partition creation because my disk uses Advanced Format so I had to align the partitions manually myself using parted. I also added one EFI partition needed for booting my laptop.

Everything went really well until the end and at the final reboot I get to the grub menu, I pick the kernel and then I get thrown to initramfs command line. No password is asked before that to decrypt the LVM.

Any idea what could be wrong?

» Reply

Andreas Haerter

No. 3 @ 2011/08/16 07:49

@Merlin:

Any idea what could be wrong?

Entry in /etc/crypttab really correct? If not, you'll get the busybox. Maybe you forgot to replace /dev/sdX2 with your device when you used to following command:

echo "lvm_crypt UUID=$(ls -la /dev/disk/by-uuid | grep $(basename /dev/sdX2) | cut -d ' ' -f 9) none luks" >> /etc/crypttab

» Reply

Rajesh

No. 4 @ 2012/01/08 13:14

I followed your instruction (& went with the manual steps as I wanted to see how it was done) with Oneiric. It worked precisely as documented. Thank you very very much. I had dual boot (Windows XP and Ubuntu) on my laptop. The only additional thing I did was that before shutting down (for restart post installation), apart from the steps you mentioned was that I modified my XP boot.ini file as documented here: http://bkpavan.wordpress.com/2008/04/02/how-to-boot-linux-using-windows-bootloader-xp/. My Windows partition is completely unaffected which is great as I had backed up my data to it!

» Reply

Moritz

No. 5 @ 2012/02/20 14:01

Nice article, quite handy for people who are not into full disk encryption, yet.

What I'm missing is a discussion of the weaknesses of XTS. It is not safe for use on large crypto devices and there are thus actually situations where aes-cbc-essiv provides better resistance than aes-xts-plain.

http://www.saout.de/pipermail/dm-crypt/2009-August/000017.html

» Reply

Andreas Haerter

No. 6 @ 2012/02/22 09:12

@Moritz: Hi Moritz. Don't you think “not safe” is a little bit extreme regarding the described issues?

With a petabyte the attack success probability rate
decreases to at most eight in a trillion.

AFAIK, cbc-essiv also got some theoretical issues (watermarking…). However: I'm not a mathematician or information scientist with crypto-background. Do you have more information about the weaknesses of XTS regarding large amounts of data regarding? I especially mean the type of attacks resulting out of the XTS issues (Just Watermarking or decryption of partial/small amounts of data? Or breaking the whole encryption? …).

Thanks!

» Reply

Martin

No. 7 @ 2012/03/05 13:14

Thanks very much for the article and the hard work that went into it!

My question is regarding dual boot with another Linux distro. What are the necessary steps to get that working? Would I simply create the necessary partition inside the LVM, and assume that the two would share the same /boot partition?

» Reply

Alex

No. 8 @ 2012/03/05 16:36

Thank you for the script. Tested successfully on Lubuntu 11.04 to USB flash drive. One small problem, not sure if it's grub or something else. First, I get a blinking cursor and I have to press CTRL+ALT+F3 to see the graphics prompt to enter the passphrase. Is there a way to go straight to the prompt and to skip having to enter CTRL+ALT+F3?

» Reply

Knut

No. 9 @ 2012/03/13 21:44

I'm booting linux mint 12 and am running your script and get:

Are you sure? (Type uppercase yes): YES
Enter LUKS passphrase: 
Verify passphrase: 
device-mapper: reload ioctl failed: Invalid argument
Failed to setup dm-crypt key mapping for device /dev/sda2.
Check that kernel supports aes-xts-plain cipher (check syslog for more info).

Any idea why?

» Reply

Felix

No. 10 @ 2012/03/14 19:53

Just wanted to say thanks for this nice tutorial, it's easy to follow and it worked like a charm :).

» Reply

Anthony

No. 11 @ 2012/04/05 18:29

  $(ls -la /dev/disk/by-uuid | grep $(basename /dev/sdX2) | cut -d ' ' -f 9)
  

Installing Ubuntu 12.04, I found I had to change the end of the above to ”-f 11” – there were a couple of additional spaces in the string, so ”-f 9” didn't return the UUID.

It might be a good idea to display the output of the above to the user so it's easy to confirm that the correct string is generated.

» Reply

Oliver Lau

No. 12 @ 2012/05/09 21:37

Die manuelle Verschüsselung mit Luks funktioniert bei ubuntu Ver. 12.04 LTS von der Desktop-CD nicht mehr. Habe das mehrfach bei mir unfreiwillig testen müssen. Nach dem chroot geben die Befehle update-initramfs -u -a all aber grub-update Fehler aus. Auch gibt es Probleme mit der Systemreperatur nach dem chroot derselben Art bei mir, was mir aufgefallen ist nach dem upgrade, weil der bootloader in den Masterbootrekord der Festplatte und nicht auf meinen Stick geschrieben wurde und deshalb versehentlich von mir zerstört wurde. Ferner wird die UUID nicht in die /etc/crypttab der verschlüsselten Partition geschrieben, was eigentlich nach der Befehlfolge zu erwarten wäre.

Bei Luci hatte das alles noch bei mir funktioniert. Bin daher auf der Suche nach einer anderen Lösung. Im Moment habe ich kein Linux auf meiner Festplatte aufgrund dieser upgrade Probleme.

Oliver Lau, Einbeck

» Reply

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