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Why Use Encryption?

In the simplest terms encryption is a method for establishing privacy.

There are presently two approaches to partition level encryption data encryption and system encryption.

Data encryption, defined as encrypting a users data, provides for many benefits including:

  • Preventing unauthorized physical access to private data.
  • Some confidence in data disposal when discarding obsolete systems.

However data encryption alone has some significant drawbacks. In modern computing systems, there are many background processes that may store information about encrypted data or parts of the encrypted data itself in non-encrypted areas of the hard drive, thus reducing the effectiveness of any data encryption system in place.

System encryption, defined as the encryption of the operating system and user data, helps to address some of the inadequacies of data encryption. The benefits of system encryption over data encryption alone include:

  • Preventing unauthorized physical access to operating system files
  • Preventing unauthorized physical access to private data that may cached by the system.

In the context of overall system security, system encryption should be viewed as an adjunct to the existing security mechanisms of the operating system that focuses on physical attempts to breach system security which includes:

  • Attempts to bypass the operating system by inserting a boot CD/USB
  • Copying, modifying, or removing the hard disk drives when the computer is off

Despite the use of system encryption, there are still points of physical insecurity. These issues revolve around the /boot partition which must remain unencrypted in order for the machine to properly boot. However, system encryption is presently the best way to minimize the loss of data privacy by physical attempts at invasion.

Warning: Any encryption method employed is only as good as its associated key management. Partition level encryption does not protect you from all forms of security compromise. There are ways to break into computers while they are powered on that are unaffected by disk level encryption. Read the caveats section below!

What Methods are Available for System Encryption?

There are multiple current methods that can be employed for system encryption, including:

loop-AES (loop-AES)
loop-AES is a descendant of cryptoloop and is a secure and fast solution to system encryption.
However loop-AES is considered less user-friendly than other options as it requires non-standard kernel support.
standard device-mapper encryption (dm-crypt)
This is the standard device mapper which can be used for those who like to have control over all aspects partition management.
LUKS for dm-crypt (LUKS)
LUKS stores all of the needed setup information for dm-crypt on the disk itself and abstracts partition and key management in an attempt to improve ease of use.
Briefly some key features that LUKS provides include:
  • Support for either passphrase or keyfiles as encryption keys
  • Per partition key creation and revocation
  • Multiple passphrases or keyfiles for a particular partition


For any type of encryption the security of your privacy is dependent on two things:

Key Complexity and Availability

The user-provided key used for encryption, whether a passphrase or a keyfile, must be complex enough that is it not easy to guess. Having a strong encryption algorithm does nothing to provide privacy if the key used for encryption is too simple. The tenets of strong keys are based on length and randomness. There are many sources available with instructions on how to create strong encryption keys.

Part of key complexity is key availability. For example a complex key written on a sticky note pasted to the computer's keyboard would not provide much in the way privacy. Therefore in addition to creating a strong key, maintaining it in a secure location is necessary as well.

Encryption Algorithm

There are many peer-reviewed encryption algorithms in existence. The encryption algorithms and block ciphers used in any of the mentioned methods for applying encryption in this wiki page are considered strong algorithms that have been subjected to cryptographic review by the cryptography community.

discard/TRIM support for solid state disks

Solid state disk users should be aware that by default, Linux's full-disk encryption mechanisms will not forward TRIM commands from the filesystem to the underlying disk. The device-mapper maintainers have made it clear that TRIM support will never be enabled by default on dm-crypt devices because of the potential security implications; if TRIM support were enabled, an attacker may be able to tell which blocks have been used, how many blocks have been used, and other information that is exposed directly to the device when a TRIM is issued.

It may be possible to determine the filesystem utilized by your encrypted device through the data that is leaked by TRIM. Furthermore, any information that may be derived by a profile of block usage may be exposed by enabling TRIM support on an encrypted device.

As of linux version 3.1, support for dm-crypt TRIM pass-through can be toggled upon device creation or mount with dmsetup. Support for this option also exists in cryptsetup version 1.4.0 and up. To add support during boot, you will need to add ":allow-discards" to the cryptdevice option. The option should look like this:


For more information, including specific commands and details on dm-crypt TRIM pass-through, see these mailing list threads:


System Encryption

System encryption provides security against unauthorized physical access to a machine that is powered off. It does not effect any security advantages for a system that is powered on with its partitions mounted in an unencrypted state. For a powered on user-accessible system the normal precautions to prevent viruses, trojans, worms, or other attempts to access private data should be exercised. Furthermore, system encryption has been shown to be penetrable in cases where a system has been recently shut down. This is due to the fact that cessation of power does not immediately degrade data that was stored in RAM prior to shutdown. Therefore someone with physical access to your computer within a few moments of shutdown could cool the RAM modules and use them extract your encryption key - thus obtaining access to your data.

Note: System Encryption assumes encryption of all mounted partitions: this includes all partitions except for /boot - meaning that the root file system, swap partition, and all other partitions must be encrypted. If the swap, /tmp, or root filesystems are unencrypted, only Data Encryption level of security has been accomplished.

Data Encryption

There are two common forms of data encryption:

  • Encryption of data partitions on the same physical disk as the system.
  • Encryption of data partitions on separate physical disks from the system.
Encryption of data partitions on the same physical disk as the system

The most common form of data encryption is encrypting the /home partition.

In cases where the encrypted data are located on the same physical disk as the system accessing the drive the privacy of data has already been decreased by orders of magnitude when compared to system encryption. The reason for this is that the host operating systems employ background methods to assist the user in the access and management of their data. The problem lies in where these processes store this data which is most commonly in the unencrypted system partition.

For example, mlocate will scan all currently mounted file systems regularly and write the list of filenames to /var/lib/mlocate/mlocate.db, which is located in the non-encrypted root or /var partition. Thus an attacker will have a list of all filenames for that computer, even the ones on the encrypted /home partition, readily available to assist them in accessing the encrypted data present on the disk.

Some have compared this to reducing the level of security from partition-based encryption to filesystem level encryption like System Encryption with eCryptfs.

Encryption of data partitions on separate physical disks from the system

Popular forms of data encryption on physically separate partitions include the encryption of removable media such as:

  • USB Flash Drives
  • External Hard Disk Drives or Separate Internal Hard Disk Drives
  • CD/DVD/Blu-Ray Optical Media
  • Magnetic Storage Media

The most important part of this form of data encryption is to remember that the encryption protects the privacy of the data that is located within the encrypted media only when it is not mounted. Data encryption does not protect the privacy of data once it is made accessible to a system. For example, attaching an encrypted USB flash drive, and subsequently decrypting a file for use temporarily on a non-secured system could result in remnants of that file existing on the host system in an unencrypted form.

Initial Setup

Overview and Preparation

The Arch installer comes with all the tools required for system encryption. Setup of encrypted partitions can be accomplished either manually prior to executing the arch installer or using the menu interface from the arch installer itself. The installation of an encrypted system is largely the same as installing an unencrypted system, so you can follow the Official Arch Linux Install Guide or the Beginners' Guide after the encrypted partitions are set up.

Routine creation of an encrypted system follows these general steps:

  • Secure erasure of the hard disk drive(s)
  • Partitioning and setup of encryption (LVM optional)
  • Routine package selection and installation
  • System Configuration
Warning: Encrypting a partition will erase everything currently on that partition. Please make appropriate data backups prior to starting.

Secure Erasure of the Hard Disk Drive

Secure erasure of the hard disk drive involves overwriting the entire drive with random data.

Note: Overwriting a hard disk drive multiple times with random data serves no purpose. Data existing prior to overwriting cannot be recovered after it has been overwritten. Overwriting Hard Drive Data: The Great Wiping Controversy

Why perform secure of erasure of a drive?

There are two types of hard disk drives, new and used, both kinds should be securely overwritten. The reasoning is slightly different for each but the goal is to help ensure the privacy of data located within the encrypted partitions.

New Hard Disk Drives
In hard drives that have been directly purchased from a manufacturer there is no preexisting private data to protect. The problem is that there is no consistency in what is presently on the drive. Ideally the drive should be completely filled with random bits. However some drives have been overwritten completely with zeros. Therefore once the drive is used to write encrypted data, it is relatively simple to identify where the encrypted data ends and the zeroed data begins compared to a drive that was written with random data before usage as an encrypted drive. Since an encrypted partition is supposed to be indistinguishable from random data, the lack of random data on a zeroed drive makes an encrypted drive an easier target for cryptanalysis.
Used Hard Disk Drives
Repartitioning or reformatting a used hard drive removes the file system structure for identifying where the original data was located while leaving the actual data intact on the drive itself. It is relatively straightforward using data tools like Foremost to access the remnant data. Therefore hard drives should be securely overwritten with random data prior to encryption to prevent unintentional data recovery.

Overwriting a hard disk drive with random data

There are two sources of random data commonly used for securely overwriting hard disk partitions.

  • /dev/urandom
  • badblocks
Using urandom
#dd if=/dev/urandom of=/dev/<drive> bs=1M

Where /dev/<drive> is the drive to be encrypted.

Note: Using /dev/urandom will take a long time to completely overwrite a drive with "random" data. In the strictest sense, /dev/urandom is less random than /dev/random; however, /dev/random uses the kernel entropy pool and will halt overwriting until more input entropy once this pool has been exhausted. This makes the use of /dev/random for overwriting hard disks impractical.
Note: Users may also find that /dev/urandom takes an excessively long time on large drives of several hundred gigabytes or more (more than twenty-four hours). Frandom offers a faster alternative.
Note: You can retrieve progress of the dd command with this command: kill -USR1 $(pidof dd)
Using badblocks
#badblocks -c 10240 -wsvt random /dev/<drive>

Where /dev/<drive> is the drive to be encrypted.

Note: The badblocks command overwrites the drive at a much faster rate by generating data that is not truly random.

See also badblocks.

Tip: In deciding which method to use for secure erasure of a hard disk drive, remember that this will not need to be performed more than once for as long as the drive is used as an encrypted drive.


After the drive has been securely overwritten, it is time to create partitions and begin setting up an encrypted system.

There are multiple ways to create disk partitions:

LUKS is compatible with systems that require LVM and/or RAID as well as with with standard primary, extended, and logical partitions.

Standard Partitions

These are the partitions that most people are familiar with. They come in three flavors: primary partitions, extended partitions, and logical partitions.

Primary Partitions
These are the normal partitions recognized by the system BIOS. There can be up to four of these stored in the MBR.
Extended Partitions
These are primary partitions that also define another partition within themselves. Extended partitions were created to work around the original limit of four primary partitions.
Logical Partitions
These are the partitions that are defined within extended partitions.

LVM: Logical Volume Manager

The LVM allows for creation of volume groups for systems that require complex combinations of multiple hard disk drives and partitions that are not possible with standard partitions. LVM is covered in detail in the Arch Linux LVM Wiki Article which is recommended reading prior to continuing with the instructions on setting up LUKS with LVM located below.

How does LVM fit into the overall system?

There is a growing preference towards logical volume management of LUKS encrypted physical media (LVM on LUKS). It is possible there may exist usage scenarios where encrypting logical volumes rather than physical disks is required (LUKS on LVM). However, the deployment of LVM on LUKS is considered much more generalizable. One reason for this is that using LUKS as the lowest level of infrastructure most closely approximates the deployment of physical disks with built-in hardware encryption. In this case, logical volume management would be layered on top of the hardware encryption – usage of LUKS would be superfluous.

Creating Disk Partitions

Disk partitions are created using:

# cfdisk

This will display a graphical interface for creating disk partitions.

There are two required partitions for any encrypted system:

A root file system
  • /
  • Will be encrypted and store all system and user files (/usr, /bin, /var, /home, etc.)
An initial boot partition
  • /boot
  • Will not be encrypted; the bootloader needs to access the /boot directory where it will load the initramfs/encryption modules needed to load the rest of the system which is encrypted (see Mkinitcpio for details). For this reason, /boot needs to reside on its own, unencrypted partition.
Note: A swap partition is optional; it can be encrypted with dm-crypt/LUKS. See Encrypting the Swap Partition for details.
Single Disk Systems

Depending on the system demands, there may be additional partitions desired. These partitions can be individually created at this level by defining separate primary or extended/logical partitions. However, if LVM is to be used, the space unoccupied by /boot and swap should be defined as single large partition which will be divided up later at the LVM level.

Multiple Disk Systems

In systems that will have multiple hard disk drives, the same options exist as a single disk system. After the creation of the /boot and swap partitions, the remaining free space on physical disks can divided up into their respective partitions at this level, or large partitions can define all free space per physical disk with intent to partition them within the LVM.

Configuring LUKS

Creating LUKS partitions with a passphrase is supported by the /arch/setup program.

This section of the Wiki will cover how to manually utilize LUKS from the command line to encrypt a system.

The steps for accomplishing this through the graphical installer are very similar and can be located in the dialogue for manual configuration of the hard drive.

Mapping Physical Partitions to LUKS

Once the desired partitions are created it is time to format them as LUKS partitions and then mount them through the device mapper.

When creating LUKS partitions they must be associated with a key.

A key is either a:

  • Passphrase
  • Keyfile

It is possible to define up to 8 different keys per LUKS partition.

Using LUKS to Format Partitions with a Passphrase

Cryptsetup is used to interface with LUKS for formatting, mounting and unmounting encrypted partitions.

A full list of options cryptsetup accepts can be found in the [Cryptsetup Manpage]

The options used here are:

  • -c defines the cipher type
  • -y prompts for password confirmation on password creation
  • -s defines the key size
luksFormat addresses the LUKS extensions built into cryptsetup.

In the following examples for creating LUKS partitions, we will use the AES cipher in XTS mode; at present this is most generally used preferred cipher. Other ciphers can be used with cryptsetup, and details about them can be found here: Wikipedia:Block_cipher

Formatting LUKS Partitions

First of all make sure the device mapper kernel module is loaded by executing the following: # modprobe dm_mod

In order to format a desired partition as an encrypted LUKS partition execute:

# cryptsetup -c <cipher> -y -s <key size> luksFormat /dev/<partition name>
Enter passphrase: <password>
Verify passphrase: <password>

This should be repeated for all partitions except for /boot and possibly swap.

The example below will create an encrypted root partition using the AES cipher in XTS mode (generally referred to as XTS-AES).

cryptsetup -c aes-xts-plain -y -s 512 luksFormat /dev/sda2
Note: If hibernation usage is planned, swap must be encrypted in this fashion; otherwise, if hibernation is not a planned feature for the system, encrypting the swap file will be performed in a alternative manner.
Warning: Irrespective of the chosen partitioning method, the /boot partition must remain separate and unencrypted in order to load the kernel and boot the system.

Unlocking/Mapping LUKS Partitions with the Device Mapper

Once the LUKS partitions have been created it is time to unlock them.

The unlocking process will map the partitions to a new device name using the device mapper. This alerts the kernel that /dev/<partition name> is actually an encrypted device and should be addressed through LUKS using the /dev/mapper/<name> so as not to overwrite the encrypted data.

In order to open an encrypted LUKS partition execute:

# cryptsetup luksOpen /dev/<partition name> <device-mapper name>
Enter any LUKS passphrase: <password>
key slot 0 unlocked.
Command successful.

Usually the device mapped name is descriptive of the function of the partition that is mapped, example:

  • cryptsetup luksOpen /dev/sda2 swap
Once opened, the swap partition device address would be /dev/mapper/swap instead of /dev/sda2.
  • cryptsetup luksOpen /dev/sda3 root
Once opened, the root partition device address would be /dev/mapper/root instead of /dev/sda3.
Note: Since /boot is not encrypted, it does not need a device mapped name and will be addressed as /dev/sda1.
Warning: In order to write encrypted data into the partition it must be accessed through the device mapped name.

Using LUKS to Format Partitions with a Keyfile

What is a Keyfile?

A keyfile is any file in which the data contained within it is used as the passphrase to unlock an encrypted volume. Therefore if these files are lost or changed, decrypting the volume will no longer be possible.

Tip: Define a passphrase in addition to the keyfile for backup access to encrypted volumes in the event the defined keyfile is lost or changed.

Why use a Keyfile?

There are many kinds of keyfile. Each type of keyfile used has benefits and disadvantages summarized below:

this is my passphrase I would have typed during boot but I have placed it in a file instead

This is a keyfile containing a simple passphrase. The benefit of this type of keyfile is that if the file is lost the data it contained is known and hopefully easily remembered by the owner of the encrypted volume. However the disadvantage is that this does not add any security over entering a passphrase during the initial system start.

fjqweifj830149-57 819y4my1- 38t1934yt8-91m 34co3;t8y;9p3y-

This is a keyfile containing a block of random characters. The benefit of this type of keyfile is that it is much more resistant to dictionary attacks than a simple passphrase. An additional strength of keyfiles can be utilized in this situation which is the length of data used. Since this is not a string meant to be memorized by a person for entry, it is trivial to create files containing thousands of random characters as the key. The disadvantage is that if this file is lost or changed, it will most likely not be possible to access the encrypted volume without a backup passphrase.

where any binary file, images, text, video could be chosen as the keyfile

This is a binary file that has been defined as a keyfile. When identifying files as candidates for a keyfile, it is recommended to choose files that are relatively static such as photos, music, video clips. The benefit of these files is that they serve a dual function which can make them harder to identify as keyfiles. Instead of having a text file with a large amount of random text, the keyfile would look like a regular image file or music clip to the casual observer. The disadvantage is that if this file is lost or changed, it will most likely not be possible to access the encrypted volume without a backup passphrase. Additionally, there is a theoretical loss of randomness when compared to a randomly generated text file. This is due to the fact that images, videos and music have some intrinsic relationship between neighboring bits of data that does not exist for a text file. However this is controversial and has never been exploited publicly.

Creating a Keyfile with Random Characters

Here dd is used to generate a keyfile of 2048 bits of random characters.

# dd if=/dev/urandom of=mykeyfile bs=512 count=4

The usage of dd is similar to initially wiping the volume with random data prior to encryption. While badblocks may also be used, most key files are on the order of a few kilobytes and there is no noticeable speed difference between dd or badblocks.

Creating a new LUKS encrypted partition with a Keyfile

When creating a new LUKS encrypted partition, a keyfile may be associated with the partition on its creation using:

# cryptsetup -c <desired cipher> -s <key size> luksFormat /dev/<volume to encrypt> /path/to/mykeyfile

This is accomplished by appending the bold area to the standard cryptsetup command which defines where the keyfile is located.

Adding Additional Passphrases or Keyfiles to a LUKS Encrypted Partition

LUKS supports the association of up to 8 keys with any single encrypted volume. Keys can be either keyfiles or passphrases.

Once an encrytped partition has been created, the initial key is associated at slot 0. Additional keys will occupy slots 1–7.

The addition of new keys to an encrypted partition is accomplished using cryptsetup with the luksAddKey extension.

# cryptsetup luksAddKey /dev/<encrypted volume> /path/to/mykeyfile

Where /dev/<encrypted volume> is the volume that is to have the new key associated with it.

If the bolded area is present, cryptsetup will look for the keyfile defined at that location to associate with the encrypted volume specified.

Storing the Key File

External Storage on a USB Drive

Preparation for permanent device names

For reading the file from an USB stick it is important to access it through a permanent device name. The numbering of the normal device names e.g. /dev/sdb1 is somewhat arbitrary and depends on how many storage devices are attached and in what order, etc. So in order to assure that the encrypt HOOK in the initcpio finds your keyfile, you must use a permanent device name.

Quick method

A quick method (as opposed to setting up a udev rule) for doing so involves referencing your removable device by its label (or UUID). To find your label or UUID, plug in your USB drive and run the following:

# ls -l /dev/disk/by-label/
lrwxrwxrwx 1 root root 10 12. Feb 10:11 Keys -> ../../sdb1


# ls -l /dev/disk/by-uuid/
lrwxrwxrwx 1 root root 10 12. Feb 10:11 4803-8A7B -> ../../sdb1

In this case, I labeled the vfat partition on my USB drive as "Keys" so my device is always symlinked in /dev/disk/by-label/Keys, or if I had wanted to use the UUID I would find /dev/disk/by-uuid/4803-8A7B. This allows me to have a consistent naming of my USB devices regardless of the order they are plugged into the system. These device names can be used in the "cryptkey" kernel option or any where else. Filesystem UUIDs are stored in the filesystem itself, meaning that the UUID will be the same if you plug it into any other computer, and that a dd backup of it will always have the same UUID since dd does a bitwise copy.

Note: If you plan to store the keyfile between MBR and the 1st partition you cannot use this method, since it only allows access to the partitions (sdb1, sdb2, ...) but not to the USB device (sdb) itself. Create a udev rule instead as described in the following section.

Using udev

Optionally you may choose to set up your flash drive with a udev rule. There is some documentation in the Arch wiki about that already; if you want more in-depth, structural info, read this guide. Here is quickly how it goes.

Get the serial number from your USB flash drive:

lsusb -v | grep -A 5 Vendor

Create a udev rule for it by adding the following to a file in /etc/udev/rules.d/, such as 8-usbstick.rules:

KERNEL=="sd*", ATTRS{serial}=="$SERIAL", SYMLINK+="$SYMLINK%n"

Replace $SYMLINK and $SERIAL with their respective values. %n will expand to the partition (just like sda is subdivided into sda1, sda2, ...). You do not need to go with the 'serial' attribute. If you have a custom rule of your own, you can put it in as well (e.g. using the vendor name).

Rescan your sysfs:

udevadm trigger

Now check the contents of /dev:

ls /dev

It should show your device with your desired name.

Generating the keyfile

Optionally you can mount a tmpfs for storing the temporary keyfile.

# mkdir ./mytmpfs
# mount tmpfs ./mytmpfs -t tmpfs -o size=32m
# cd ./mytmpfs

The advantage is that it resides in RAM and not on a physical disk, so after unmounting your keyfile is securly gone. So copy your keyfile to some place you consider as secure before unmounting. If you are planning to store the keyfile as a plain file on your USB device, you can also simply execute the following command in the corresponding directory, e.g. /media/sdb1

The keyfile can be of arbitrary content and size. We will generate a random temporary keyfile of 2048 bytes:

# dd if=/dev/urandom of=secretkey bs=512 count=4

If you stored your temporary keyfile on a physical storage device, remember to not just (re)move the keyfile later on, but use something like

cp secretkey /destination/path
shred --remove --zero secretkey

to securely overwrite it. (However due to journaling filesystems this is also not 100% secure.)

Add the temporary keyfile with cryptsetup:

# cryptsetup luksAddKey /dev/sda2 secretkey
Enter any LUKS passphrase:
key slot 0 unlocked.
Command successful.

Storing the keyfile

To store the key file, you have two options. The first is less risky than the other, but perhaps a bit more secure (if you consider security by obscurity as more secure). In any case you have to do some further configuration, if not already done above.

Configuration of initcpio

You have to add two extra modules in your /etc/mkinitcpio.conf, one for the drive's file system and one for the codepage. Further if you created a udev rule, you should tell mkinitcpio about it:

MODULES="ata_generic ata_piix nls_cp437 vfat"

In this example it is assumed that you use a FAT formatted USB drive. Replace those module names if you use another file system on your USB stick (e.g. ext2) or another codepage. Users running the stock Arch kernel should stick to the codepage mentioned here.

Additionally, insert the usb hook somewhere before the encrypt hook.

HOOKS="... usb encrypt ... filesystems ..."

If you have a non-US keyboard, it might prove useful to load your keyboard layout before you are prompted to enter the password to unlock the root partition at boot. For this, you will need the keymap hook before encrypt.

Generate a new image (maybe you should backup a copy of your old kernel26.img first):

mkinitcpio -g /boot/kernel26.img

Storing the key as a plain (visible) file

Be sure to choose a plain name for your key – a bit of 'security through obscurity' is always nice ;-). Avoid using dotfiles (hidden files) – the encrypt hook will fail to find the keyfile during the boot process.

You have to add a kernel parameter in your /boot/grub/menu.lst (GRUB). It should look something like this:

kernel /vmlinuz26 root=/dev/hda3 ro vga=791 cryptkey=/dev/usbstick:vfat:/secretkey

This assumes /dev/usbstick is the FAT partition of your choice. Replace it with /dev/disk/by-... or whatever your device is.

That is all, reboot and have fun!

Storing the key between MBR and 1st partition

We will write the key directly between the Master Boot Record (MBR) and the first partition.

Warning: You should only follow this step if you know what you are doing -- it can cause data loss and damage your partitions or MBR on the stick!

If you have a bootloader installed on your drive you have to adjust the values. E.g. GRUB needs the first 16 sectors (actually, it depends on the type of the file system, so do not rely on this too much), so you would have to replace seek=4 with seek=16; otherwise you would overwrite parts of your GRUB installation. When in doubt, take a look at the first 64 sectors of your drive and decide on your own where to place your key.

Optional If you do not know if you have enough free space before the first partition, you can do

dd if=/dev/usbstick of=64sectors bs=512 count=64   # gives you copy of your first 64 sectors
hexcurse 64sectors                                 # determine free space
xxd 64sectors | less                               # alternative hex viewer

Write your key to the disk:

dd if=secretkey of=/dev/usbstick bs=512 seek=4

If everything went fine you can now overwrite and delete your temporary secretkey as noted above. You should not simply use rm as the keyfile would only be unlinked from your filesystem and be left physically intact.

Now you have to add a kernel parameter in your /boot/grub/menu.lst file (GRUB); it should look something like this:

kernel /vmlinuz26 root=/dev/hda3 ro vga=791 cryptkey=/dev/usbstick:2048:2048

Format for the cryptkey option:


OFFSET and SIZE match in this example, but this is just coincidence - they can differ (and often will). An other possible example could be

kernel /vmlinuz26 root=/dev/hda3 ro vga=791 cryptkey=/dev/usbstick:8192:2048

That is all, reboot and have fun! And look if your partitions still work after that ;-).

Encrypting the Swap partition

Without suspend-to-disk support

In systems where suspend to disk is not a desired feature, it is possible to create a swap file that will have a random passphrase with each boot.

This is accomplished by using dm-crypt directly without LUKS extensions.

Append a similar line to /etc/crypttab to set up a randomly encrypted swap partition:

<device-mapper name> <swap physical partition> SWAP "-c aes-xts-plain -h whirlpool -s 512"


  • <device-mapper name> represents the name you want to use as label in /etc/fstab
  • <swap physical partition> should be the ID of the actual partition.
    Warning: You should use IDs here because if there are multiple hard drives installed in the system, their naming order (sda, sdb,...) can occasionally be scrambled upon boot and thus the swap would be created over a valuable file system, destroying its content. ls -l /dev/disk/*/* | grep sdl7 should help you to find the desired partition.
  • SWAP identifies the partition as a swap partition
  • -c defines a cipher
  • -h defines a hash algorithm
  • -s defines the key size

Example line (where /dev/sdl7 is the physical partition and LABEL=swap the desired label):

swap /dev/disk/by-id/scsi-SATA_Hitachi_HDS7220_JK1130YAGX0R1T-part7 SWAP "-c aes-xts-plain -h whirlpool -s 512"
Maps /dev/sdl7 to /dev/mapper/swap as a swap partition which we can now add in /etc/fstab like a normal swap.

If the partition chosen for swap was previously a LUKS partition, crypttab will not overwrite the partition to create a swap partition. This is a safety measure to prevent data loss from accidental mis-identification of the swap partition in crypttab. In order to use such a partition the LUKS header must be removed. This can be accomplished with:

# dd if=/dev/zero of=/dev/sdl7 bs=1M

With suspend-to-disk support

Warning: Do not use this setup with a key file. Please read about the issue reported here

To be able to resume after suspending the computer to disk (hibernate), it is required to keep the swap filesystem intact. Therefore, it is required to have a pre-existent LUKS swap partition, which can be stored on the disk or input manually at startup. Because the resume takes place before /etc/crypttab can be used, it is required to create a hook in /etc/mkinitcpio.conf to open the swap LUKS device before resuming. The following setup has the disadvantage of having to insert a key manually for the swap partition.

If you want to use a partition which is currently used by the system, you have to disable it first:

# swapoff /dev/<device>

To create the swap partition, follow steps similar to those described in mapping partitions above.

  • Format the partition you want to use as swap with the cryptsetup command. For performance reasons, you might want to use different ciphers with different key sizes.
# cryptsetup -c aes-xts-plain -s 512 -h sha512 -v luksFormat /dev/<device>

Check the result with:

# cryptsetup luksDump /dev/<device>
  • Open the partition in /dev/mapper:
# cryptsetup luksOpen /dev/<device> swapDevice
  • Create a swap filesystem inside the mapped partition:
# mkswap /dev/mapper/swapDevice

Now you should have a LUKS swap partition which asks for the passphrase before mounting. Make sure you remove any line in /etc/crypttab which uses this device. Now you have to create a hook to open the swap at boot time.

  • Create a hook file containing the open command:
 # vim: set ft=sh:
 run_hook ()
     cryptsetup luksOpen /dev/<device> swapDevice
  • Then create and edit the hook setup file:
 # vim: set ft=sh:
 build ()
 help ()
   This opens the swap encrypted partition /dev/<device> in /dev/mapper/swapDevice
  • Add the hook openswap in the HOOKS array in /etc/mkinitcpio.conf, before filesystem, but after encrypt which is mandatory as well. Do not forget to add the resume hook between openswap and filesystem as well.
  • Regenerate the boot image:
# mkinitcpio -p linux
  • Add the mapped partition to /etc/fstab by adding the following line:
/dev/mapper/swapDevice swap swap defaults 0 0
  • Set up your system to resume from /dev/mapper/swapDevice. For example, if you use GRUB with kernel hibernation support, add resume=/dev/mapper/swapDevice to the kernel line in /boot/grub/menu.lst. A line with encrypted root and swap partitions can look like this:
kernel /vmlinuz26 cryptdevice=/dev/sda2:rootDevice root=/dev/mapper/rootDevice resume=/dev/mapper/swapDevice ro

At boot time, the openswap hook will open the swap partition so the kernel resume may use it. If you use special hooks for resuming from hibernation, make sure they are placed after openswap in the HOOKS array. Please note that because of initrd opening swap, there is no entry for swapDevice in /etc/crypttab needed in this case.

Using a swap file for suspend-to-disk support

  • Choose a mapped partition (e.g. /dev/mapper/rootDevice) whose mounted filesystem (e.g. /) contains enough free space to hold the entire contents of your system's RAM. For example, if your system has 4 GiB RAM, then you need at least that much free space on the mounted filesystem of your chosen mapped partition for the swap file.
  • Create the swap file (e.g. /swapfile) inside the mounted filesystem of your chosen mapped partition. Be sure to activate it with swapon and also add it to your /etc/fstab file afterward.
  • Set up your system to resume from your chosen mapped partition. For example, if you use GRUB with kernel hibernation support, add resume=your chosen mapped partition and resume_offset=see calculation command below to the kernel line in /boot/grub/menu.lst. A line with encrypted root partition can look like this:
kernel /vmlinuz26 cryptdevice=/dev/sda2:rootDevice root=/dev/mapper/rootDevice resume=/dev/mapper/rootDevice resume_offset=123456789 ro

You can calculate the resume_offset of your swap file like this:

# filefrag -v /swapfile | awk '{if($1==0){print $3}}'
  • Add the resume hook to your etc/mkinitcpio.conf file and rebuild the image afterward:
HOOKS="... encrypt resume ... filesystems ..."

Installing the system

Now that /dev/mapper/root and /dev/mapper/home are in place, we can enter the regular Arch setup script to install the system into the encrypted volumes.

# /arch/setup
Note: Most of the installation can be carried out normally. However, there are a few areas where it is important to make certain selections. These are marked below.

Prepare hard drive

Skip the Partitioning and Auto-Prepare steps and go straight to manual configuration. Instead of choosing the hardware devices (/dev/sdaX) directly, you have to select the mapper devices created above. Choose /dev/mapper/root for your root and /dev/mapper/home as /home partition respectively and format them with any filesystem you like. The same is valid for a swap partition which is set up like the /home partition. Make sure you mount /dev/sda1 as the /boot partition, or else the installer will not properly set up the bootloader.

Select and Install packages

Select and install the packages as usual: the base package contains all required programs.

Configure System

{{Note|The encrypt hook is only needed if your root partition is a LUKS partition (or a LUKS partition that needs to be mounted before root). The encrypt hook is not needed if any other partition (swap, for example) is encrypted. System initialization scripts (/etc/rc.sysinit and /etc/crypttab among others) take care of those.

Afterwards you can check the files presented to you by the installer, the most important one being /etc/mkinitcpio.conf. For detailed information about mkinitcpio and its configuration refer to Mkinitcpio. You have to make sure that your HOOKS array in /etc/mkinitcpio.conf looks something like this:

HOOKS="... encrypt ... filesystems ..."

It is important that the encrypt hook comes before the filesystems hook. If you store your key on an external USB device (e.g. a USB stick), you need to add the USB hook too:

HOOKS="... usb encrypt ... filesystems ..."

For safety, add usb before encrypt because the hooks are run in the order they appear. If you need support for foreign keymaps for your encryption password, you have to specify the hook keymap as well. I suggest putting this in /etc/mkinitcpio.conf immediately before encrypt.

If you have a USB keyboard, you will need the usbinput hook in /etc/mkinitcpio.conf. Without it, no USB keyboard will work in early userspace.

If your root partition is a LUKS partition, add the used filesystem to the MODULES section.

MODULES="... ext3 ext4 xfs ..."

Install Bootloader

GRUB: You have to make some small changes to the entries generated by the installer by replacing /dev/mapper/root with /dev/sda3. The important point to remember here is to use the same cryptdevice name you assigned when you initially unlocked your device. In this example, the device name is cryptroot; customize yours accordingly:

# (0) Arch Linux
title Arch Linux
root (hd0,0)
kernel /vmlinuz-linux cryptdevice=/dev/sda3:cryptroot root=/dev/mapper/cryptroot ro
initrd /initramfs-linux.img

For kernels older than 2.6.37, the syntax is:

# (0) Arch Linux
title Arch Linux
root (hd0,0)
kernel /vmlinuz26 root=/dev/sda3 ro
initrd /kernel26.img

LILO: Edit the Arch Linux section in /etc/lilo.conf and include a line for the append option, over the initrd, with the root=/dev/sda3 parameter. The append section makes the same kernel line as in GRUB. Also, you can omit the root option above the image option. The section looks like this:

# Arch Linux lilo section
image = /vmlinuz26
# root = /dev/sda3
 label = Arch
 initrd = /kernel26.img
 append = "root=/dev/sda3"
Note: If you want to use a USB flash drive with a keyfile, you have to append the cryptkey option. See the corresponding section below.

Exit Install

Now that the install is finished the only thing left to do is add entries to the /etc/crypttab file so you do not have to enter the passphrase for all encrypted partitions. This works only for non-root partitions e.g. /home, swap, etc.

# vi /mnt/etc/crypttab

Add the following line for the /home partition

home    /dev/sda5    "myotherpassword"

You can also use a keyfile instead of a passphrase. If not already done, create a keyfile and add the key to the corresponding LUKS partition as described above. Then add the following information to the /etc/crypttab file for automounting:

home    /dev/sda5    /path/of/your/keyfile

After rebooting you should now be presented with the text

A password is required to access the root filesystem:

followed by a prompt for a LUKS password. Type it in and everything should boot. Once you've logged in, have a look at your mounted partitions by typing mount. You should have /dev/mapper/root mounted at / and, if you set up a separate encrypted home partition, /dev/mapper/home mounted at /home. If you set up encrypted swap, swapon -s should have /dev/mapper/swap listed as your swap partition.

Note: Eventually the text prompting for the password is mixed up with other boot messages. So the boot process may seem frozen at first glance, but it is not, simply enter your password and press return.

Remote unlocking of the root (or other) partition

If you want to be able to reboot a fully LUKS-encrypted system remotely, or start it with a Wake-on-LAN service, you will need a way to enter a passphrase for the root partition/volume at startup. This can be achieved by running the net hook along with an SSH server in initrd. Install the dropbear_initrd_encryptAUR package from the AUR and follow the post-installation instructions. Replace the encrypt hook with dropbear encryptssh in /etc/mkinitcpio.conf. Put the net hook early in the HOOKS array if your DHCP server takes a long time to lease IP addresses.

If you would simply like a nice solution to mount other encrypted partitions (such as /home)remotely, you may want to look at this forum thread.

Note: Acutally trim will not work with this script because it is not yet updated to the latest encrypt hook, so it is not able to parse -–allow-discards from /boot/grub/menu.lst. (Version: dropbear_initrd_encrypt 0.8-16). You won't notice any error when using online discard, but you see an error when you try to use fstrim.For a temporary solution just add -–allow-discards to every cryptsetup line of /lib/initcpio/install/dropbear(1 line) and /lib/initcpio/hooks/encryptssh(3 lines)

Backup the cryptheader

If the header of your encrypted partition gets destroyed, you will not be able to decrypt your data. Therefore, having a backup of the headers and storing them on another disk might be a good idea.

Attention: Many people recommend NOT backing up the cryptheader, but even so it's a single point of failure! In short, the problem is that LUKS is not aware of the duplicated cryptheader, which contains the master key which is used to encrypt all files on your partition. Of course this master key is encrypted with your passphrases or keyfiles. But if one of those gets compromised and you want to revoke it you have to do this on all copies of the cryptheader! I.e. if someone has got your cryptheader and one of your keys he can decrypt the master key and access all your data. Of course the same is true for all backups you create of your partions. So you decide if you are one of those paranoids brave enough to go without a backup for the sake of security or not. See also [1]Template:Linkrot for further details on this.

Note: You can also back up the header into a tmpfs/ramfs and encrypt it with gpg or whatever before writing it to a physical disk. Of course you can wrap your encrypted backup into another encryption layer and so on until you feel safe enough :-)



First you have to find out the payload offset of the crypted partition (replace sdaX with the corresponding partition)

cryptsetup luksDump /dev/sdaX | grep "Payload offset"
Payload offset:	4040

Now that you know the value, you can backup the header with a simple dd command

dd if=/dev/sdaX of=./backup.img bs=512 count=4040

Using cryptsetup

You can also use the luksHeaderBackup command instead:

cryptsetup luksHeaderBackup /dev/sdaX --header-backup-file ./backup.img


Be careful before restore: make sure that you chose the right partition (again replace sdaX with the corresponding partition). Restoring the wrong header or restoring to an unencrypted partition will cause data loss.


Again, you will need to the same values as when backing up:

dd if=./backup.img of=/dev/sdX bs=512 count=4040

Using cryptsetup

Or you can use the luksHeaderRestore command:

cryptsetup luksHeaderRestore /dev/sdaX --header-backup-file ./backup.img

Note: All the keyslot areas are overwritten; only active keyslots from the backup file are available after issuing this command.

Encrypting a loopback filesystem

[This paragraph has been merged from another page; its consistency with the other paragraphs should be improved]

Preparation and mapping

First, start start by creating an encrypted container!

dd if=/dev/urandom of=/bigsecret bs=1M count=10

This will create the file bigsecret with a size of 10 megabytes.

losetup /dev/loop0 /bigsecret

This will create the device node /dev/loop0, so that we can mount/use our container.

Note: If it gives you the error /dev/loop0: No such file or directory, you need to first load the kernel module with modprobe loop. These days (Kernel 3.2) loop devices are created on demand. Ask for a new loop device with losetup -f.
cryptsetup luksFormat /dev/loop0

This will ask you for a password for your new container file.

Note: If you get an error like Command failed: Failed to setup dm-crypt key mapping. Check kernel for support for the aes-cbc-essiv:sha256 cipher spec and verify that /dev/loop0 contains at least 133 sectors, then run modprobe dm-mod.
cryptsetup luksOpen /dev/loop0 secret

The encrypted container is now available through the device file /dev/mapper/secret. Now we are able to create a partition in the container:

mkfs.ext2 /dev/mapper/secret

and mount it...

mkdir /mnt/secret
mount -t ext2 /dev/mapper/secret /mnt/secret

We can now use the container as if it was a normal partition! To unmount the container:

umount /mnt/secret
cryptsetup luksClose secret
losetup -d /dev/loop0 # free the loopdevice.

so, if you want to mount the container again, you just apply the following commands:

losetup /dev/loop0 /bigsecret
cryptsetup luksOpen /dev/loop0 secret
mount -t ext2 /dev/mapper/secret /mnt/secret

Encrypt using a key-file

Let us first generate a 2048 byte random keyfile:

dd if=/dev/urandom of=keyfile bs=1k count=2

We can now format our container using this key

cryptsetup luksFormat /dev/loop0 keyfile

or our partition :

cryptsetup luksFormat /dev/hda2 keyfile

Once formatted, we can now open the LUKS device using the key:

cryptsetup -d keyfile luksOpen /dev/loop0 container

You can now like before format the device /dev/mapper/container with your favorite filesystem and then mount it just as easily.

The keyfile is now the only key to your file. I personally advise encrypting your keyfile using your private GPG key and storing an off-site secured copy of the file.

Resizing the loopback filesystem

First we should unmount the encrypted container:

umount /mnt/secret
cryptsetup luksClose secret
losetup -d /dev/loop0 # free the loopdevice.

After this we need to expand our container file with the size of the data we want to add:

dd if=/dev/urandom bs=1M count=1024 | cat - >> /bigsecret

Be careful to really use TWO >, or you will override your current container!

You could use /dev/zero instead of /dev/urandom to significantly speed up the process, but with /dev/zero your encrypted filesystems will not be as secure. (A better option to create random data quicker than /dev/urandom is frandom [2], available from the AUR).

Now we have to map the container to the loop device:

losetup /dev/loop0 /bigsecret
cryptsetup luksOpen /dev/loop0 secret

After this we will resize the encrypted part of the container to the maximum size of the container file:

cryptsetup resize secret

Finally, we can resize the filesystem. Here is an example for ext2/3/4:

e2fsck -f /dev/mapper/secret # Just doing a filesystem check, because it's a bad idea to resize a broken fs
resize2fs /dev/mapper/secret

You can now mount your container again:

mount /dev/mapper/secret /mnt/secret

Encrypting a LVM setup

It's really easy to use encryption with LVM. If you do not know how to set up LVM, then read Installing_with_Software_RAID_or_LVM.

The easiest and best method is to set up LVM on top of the encrypted partition instead of the other way around. This link here is easy to follow and explains everything: Arch Linux: LVM on top of an encrypted partition

The most important thing in setting LVM on top of encryption is that you need to have the encrypt hook before the lvm2 hook (and those two before the filesystems hook, but that's repeating) because they are processed in order.

To use encryption on top of LVM, you have to first set up your LVM volumes and then use them as the base for the encrypted partitions. That means, in short, that you have to set up LVM first. Then follow this guide, but replace all occurrences of /dev/sdXy in the guide with its LVM counterpart. (E.g.: /dev/sda5 -> /dev/<volume group name>/home).

Do not forget to add the encrypt hook in /etc/mkinitcpio.conf before the lvm2 hook, if you chose to set up encrypted partitions on top of LVM. Also remember to change USELVM in /etc/rc.conf to "yes".

LVM with Arch Linux Installer (>2009.08)

Since Arch Linux images 2009.08, LVM and dm_crypt is supported by the installer out of the box. This makes it very easy to configure your system for LVM on dm-crypt or vice versa. Actually the configuration is done exactly as without LVM: see the corresponding section above. It differs only in two aspects.

The partition and filesystem choice

Create a small, unencrypted boot partition and use the remaining space for a single partition which can later be split up into multiple logic volumes by LVM.

For a LVM-on-dm-crypt system set up the filesystems and mounting points for example like this:

/dev/sda1   raw->ext2;yes;/boot;no_opts;no_label;no_params
/dev/sda2   raw->dm_crypt;yes;no_mountpoint;no_opts;sda2crypt;-c_aes-xts-plain_-y_-s_512
/dev/mapper/sda2crypt   dm_crypt->lvm-vg;yes;no_mountpoint;no_opts;no_label;no_params
/dev/mapper/sda2crypt+  lvm-pv->lvm-vg;yes;no_mountpoint;no_opts;cryptpool;no_params
/dev/mapper/cryptpool   lvm-vg(cryptpool)->lvm-lv;yes;no_mountpoint;no_opts;cryptroot;10000M|lvm-lv;yes;no_mountpoint;no_opts;crypthome;20000M
/dev/mapper/cryptpool-cryptroot   lvm-lv(cryptroot)->ext3;yes;/;no_opts;cryptroot;no_params
/dev/mapper/cryptpool-crypthome   lvm-lv(crypthome)->ext3;yes;/home;no_opts;cryptroot;no_params

The configuration stage

  • In /etc/rc.conf set USELVM to "yes"
  • In /etc/mkinitcpio.conf add the encrypt hook before the lvm2 hook in the HOOKS array, if you set up LVM on top of the encrypted partition.

That is it for the LVM & dm_crypt specific part. The rest is done as usual.

Applying this to a non-root partition

You might get tempted to apply all this fancy stuff to a non-root partition. Arch does not support this out of the box, however, you can easily change the cryptdev and cryptname values in /lib/initcpio/hooks/encrypt (the first one to your /dev/sd* partition, the second to the name you want to attribute). That should be enough.

The big advantage is you can have everything automated, while setting up /etc/crypttab with an external key file (i.e. the keyfile is not on any internal hard drive partition) can be a pain - you need to make sure the USB/FireWire/... device gets mounted before the encrypted partition, which means you have to change the order of /etc/fstab (at least).

Of course, if the cryptsetup package gets upgraded, you will have to change this script again. However, this solution is to be preferred over hacking /etc/rc.sysinit or similar files. Unlike /etc/crypttab, only one partition is supported, but with some further hacking one should be able to have multiple partitions unlocked.

If you want to do this on a software RAID partition, there is one more thing you need to do. Just setting the /dev/mdX device in /lib/initcpio/hooks/encrypt is not enough; the encrypt hook will fail to find the key for some reason, and not prompt for a passphrase either. It looks like the RAID devices are not brought up until after the encrypt hook is run. You can solve this by putting the RAID array in /boot/grub/menu.lst, like

kernel /boot/vmlinuz26 md=1,/dev/hda5,/dev/hdb5

If you set up your root partition as a RAID, you will notice the similarities with that setup ;-). GRUB can handle multiple array definitions just fine:

kernel /boot/vmlinuz26 root=/dev/md0 ro md=0,/dev/sda1,/dev/sdb1 md=1,/dev/sda5,/dev/sdb5,/dev/sdc5

LVM and dm-crypt manually (short version)


If you are smart enough for this, you will be smart enough to ignore/replace LVM-specific things if you do not want to use LVM.

Note: This brief uses reiserfs for some of the partitions, so change this accordingly if you want to use a more "normal" file system, like ext4.

Partitioning scheme

/dev/sda1 -> /boot
/dev/sda2 -> LVM

The commands

cryptsetup -d /dev/random -c aes-xts-plain -s 512 create lvm /dev/sda2
dd if=/dev/urandom of=/dev/mapper/lvm
cryptsetup remove lvm
lvm pvcreate /dev/sda2
lvm vgcreate lvm /dev/sda2
lvm lvcreate -L 10G -n root lvm
lvm lvcreate -L 500M -n swap lvm
lvm lvcreate -L 500M -n tmp lvm
lvm lvcreate -l 100%FREE -n home lvm
cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/root
cryptsetup luksOpen /dev/lvm/root root
mkreiserfs /dev/mapper/root
mount /dev/mapper/root /mnt
dd if=/dev/zero of=/dev/sda1 bs=1M
mkreiserfs /dev/sda1
mkdir /mnt/boot
mount /dev/sda1 /mnt/boot
mkdir -p -m 700 /mnt/etc/luks-keys
dd if=/dev/random of=/mnt/etc/luks-keys/home bs=1 count=256

Install Arch Linux

Run /arch/setup



Change USELVM="no" to USELVM="yes".


Put lvm2 and encrypt (in that order) before filesystems in the HOOKS array. Again, note that you are setting encryption on top of LVM.)


Change root=/dev/hda3 to root=/dev/lvm/root.

For kernel >= 2.6.30, you should change root=/dev/hda3 to the following:

cryptdevice=/dev/lvm/root:root root=/dev/mapper/root
/dev/mapper/root        /       reiserfs        defaults        0       1
/dev/sda1               /boot   reiserfs        defaults        0       2
/dev/mapper/tmp         /tmp    tmpfs           defaults        0       0
/dev/mapper/swap        none    swap            sw              0       0
swap	/dev/lvm/swap	SWAP		-c aes-xts-plain -h whirlpool -s 512
tmp	/dev/lvm/tmp	/dev/urandom	-c aes-xts-plain -s 512

After rebooting

The commands
cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/home /etc/luks-keys/home
cryptsetup luksOpen -d /etc/luks-keys/home /dev/lvm/home home
mkreiserfs /dev/mapper/home
mount /dev/mapper/home /home
home	/dev/lvm/home   /etc/luks-keys/home
/dev/mapper/home        /home   reiserfs        defaults        0       0

/ on LVM on LUKS

Make sure your kernel command line looks like this:

root=/dev/mapper/<volume-group>-<logical-volume> cryptdevice=/dev/<luks-part>:<volume-group>

For example:

root=/dev/mapper/vg-arch cryptdevice=/dev/sda4:vg

Or like this:

cryptdevice=/dev/<volume-group>/<logical-volume>:root root=/dev/mapper/root

Securing the unencrypted boot partition

Referring to an article from the ct-magazine (Issue 3/12, page 146, 01.16.2012 the following script checks all files under /boot for changes of sha1 hash, inode and occupied blocks on the hard drive. It also checks the MBR.

The script with installation instructions is available here: (Autor: Juergen Schmidt, ju at; License: GPLv2)

There is also an AUR package:

After installation do

  echo "/usr/local/bin/ &" >> /etc/rc.local

And as need to be excuted after login, add it to the autostarts.