This article describes basic usage of eCryptfs. It guides you through the process of creating a private and secure encrypted directory within your
$HOME directory to store sensitive files and private data.
In implementation eCryptfs differs from dm-crypt, which provides a block device encryption layer, while eCryptfs is an actual file-system – a stacked cryptographic file system. For comparison of the two you can refer to this table and the Disk encryption#Comparison table. One distinguished feature is that the encryption is stacked on an existing filesystem; eCryptfs can be mounted onto any single existing directory and does not require a separate partition (or size pre-allocation).
- 1 Basics
- 2 Setup & mounting
- 2.1 High-level tools (hardcoded paths)
- 2.2 ecryptfs-simple
- 2.3 Manual setup
- 3 Usage
- 4 See Also
As mentioned in the summary eCryptfs does not require special on-disk storage allocation effort, such as a separate partition or pre-allocated space. Instead, you can mount eCryptfs on top of any single directory to protect it. That includes, for example, a user's entire
$HOME directory or single dedicated directories within it. All cryptographic metadata is stored in the headers of files, so encrypted data can be easily moved, stored for backup and recovered. There are other advantages, but there are also drawbacks, for instance eCryptfs is not suitable for encrypting complete partitions which also means you cannot protect swap space with it (but you can, of course, combine it with Dm-crypt/Swap encryption). If you are just starting to set up disk encryption, swap encryption and other points to consider are covered in Disk encryption#Preparation.
To familiarize with eCryptfs a few points:
- As a stacked filesystem, a mounting of an eCryptfs directory refers to mounting a (stacked) encrypted directory to another unencrypted mount point (directory) at Linux kernel runtime.
- It is possible to share an encrypted directory between users. However, the encryption is linked to one passphrase so this must be shared as well. It is also possible to share a directory with differently encrypted files (different passphrases).
- A number of eCryptfs acronyms are used throughout the documentation:
- The encrypted directory is referred to as the lower and the unencrypted as the upper directory throughout the eCryptfs documentation and this article. While not relevant for this article, the "overlay" filesystem introduced with Linux 3.18 uses (and explains) the same upper/lower nomenclatura for the stacking of filesystems.
- the mount passphrase (or key) is what gives access to the encrypted files, i.e. unlocks the encryption. eCryptfs uses the term wrapped passphrase to refer to the cryptographically secured mount passphrase.
FEFEKrefers to a File's Encryption key Encryption Key (see kernel documentation).
FNEKrefers to a File Name Encryption Key, a key to (optionally) encrypt the filenames stored in the encrypted directory.
Before using eCryptfs, the following disadvantages should be checked for applicability.
- Ease of use
- The EncFS. package provides several different ways of setting up eCryptfs. The high-level "Ubuntu tools" are the easiest to use, but they hard-code the lower directory path and other settings, limiting their usefulness. The package also includes low-level tools which are fully configurable, but they are somewhat more difficult to use compared to alternatives like
- Network storage mounts
- eCryptfs has long-standing bugs when used on top of NFS and possibly other networked filesystems. It is always possible to use eCryptfs on a local directory and then copy the encrypted files from the local directory to a network host. However, if you want to set up eCryptfs directly on top of an NFS mount, with no local copy of the files, eCryptfs may crash or behave incorrectly. If in doubt, EncFS may be a better choice in this case.
- Sparse files
- Sparse files written to eCryptfs will produce larger, non-sparse encrypted files in the lower directory. For example, in an eCryptfs directory running
truncate -s 1G file.imgcreates a 1GB encrypted file on the underlying filesystem, with the corresponding resource (disk space, data throughput) requirements. If the same file were created on an unencrypted filesystem or a filesystem using block device encryption, it would only take a few kilobytes.
- This should be considered before encrypting large portions of the directory structure, though in most cases the disadvantages will be minor. If you need to use large sparse files, you can work around this issue by putting the sparse files in an unencrypted directory or using block device encryption for them.
Setup & mounting
Before starting, check the eCryptfs documentation. It is distributed with a very good and complete set of manual pages.
eCryptfs has been included in Linux since version 2.6.19. Start by loading the
# modprobe ecryptfs
To actually mount an eCryptfs filesystem, you need to use userspace tools provided by the package Official repositories. Unfortunately, due to the poor design of these tools, you must choose between three ways of setting up eCryptfs with different tradeoffs:available in the
- Use the high-level tools, which set things up automatically but require the lower directory to be
~/.Private/, and allow only one encrypted filesystem per user.
- Use ecryptfs-simple, available from AUR, which is an easy way to mount eCryptfs filesystems using any lower directory and upper directory.
- #Manual setup, which involves separate steps for loading the passphrase and mounting eCryptfs, but allows complete control over the directories and encryption settings.
High-level tools (hardcoded paths)
Most of the user-friendly convenience tools installed by the ecryptfs-utils package assume a very specific eCryptfs setup, namely the one that is officially used by Ubuntu (where it can be selected as an option during distro installation). Unfortunately, these choices are not just default options but are actually hard-coded in the tools. If this set-up does not suit your needs, then you can not use the convenience tools and will have to follow the steps at #Manual setup instead.
The set-up used by these tools is as follows:
- each user can have only one encrypted directory that is managed by these tools:
- either full
$HOMEdirectory encryption, or
- a single encrypted data directory (by default
~/Private/, but this can be customized).
- either full
- the lower directory for each user is always
(in the case of full home dir encryption, this will be a symlink to the actual location at
- the encryption options used are:
- cipher: AES
- key length: 16 bytes (128 bits)
- key management scheme: passphrase
- plaintext passthrough: enabled
- the configuration / control info for the encrypted directory is stored in a bunch of files at
(in the case of full home dir encryption, this will be a symlink to the actual location at
Private.mnt[plain text file] - contains the path where the upper directory should be mounted (e.g.
Private.sig[plain text file] - contains the signature used to identify the mount passphrase in the kernel keyring
wrapped-passphrase[binary file] - the mount passphrase, encrypted with the login passphrase
auto-umount[empty files] - if they exist, the
pam_ecryptfs.somodule will (assuming it is loaded) automatically mount/unmount this encrypted directory when the user logs in/out
Encrypting a data directory
For a full
$HOME directory encryption see #Encrypting a home directory
Before the data directory encryption is setup, decide whether it should later be mounted manually or automatically with the user log-in.
To encrypt a single data directory as a user and mount it manually later, run:
$ ecryptfs-setup-private --nopwcheck --noautomount
and follow the instructions. The option
--nopwcheck enables you to choose a passphrase different to the user login passphrase and the option
--noautomount is self-explanatory. So, if you want to setup the encrypted directory automatically on log-in later, just leave out both options right away.
The script will automatically create the
~/.ecryptfs/ directory structures as described in the box above. It will also ask for two passphrases:
- login passphrase
- This is the password you will have to enter each time you want to mount the encrypted directory. If you want auto-mounting on login to work, it has to be the same password you use to login to your user account.
- mount passphrase
- This is used to derive the actual file encryption master key. Thus, you should not enter a custom one unless you know what you are doing - instead press Enter to let it auto-generate a secure random one. It will be encrypted using the login passphrase and stored in this encrypted form in
~/.ecryptfs/wrapped-passphrase. Later it will automatically be decrypted ("unwrapped") again in RAM when needed, so you never have to enter it manually. Make sure this file does not get lost, otherwise you can never access your encrypted folder again! You may want to run
ecryptfs-unwrap-passphraseto see the mount passphrase in unencrypted form, write it down on a piece of paper, and keep it in a safe (or similar), so you can use it to recover your encrypted data in case the wrapped-passphrase file is accidentally lost/corrupted or in case you forget the login passphrase.
The mount point ("upper directory") for the encrypted folder will be at
~/Private by default, however you can manually change this right after the setup command has finished running, by doing:
$ mv ~/Private /path/to/new/folder $ echo /path/to/new/folder > ~/.ecryptfs/Private.mnt
To actually use your encrypted folder, you will have to mount it - see #Mounting below.
Encrypting a home directory
The wrapper script
ecryptfs-migrate-home will set up an encrypted home directory for a user and take care of migrating any existing files they have in their not yet encrypted home directory.
To run it, the user in question must be logged out and own no processes. The best way to achieve this is to log the user out, log into a console as the root user, and check that
ps -U username returns no output. You also need to ensure that you have and installed. Once the prerequisites have been met, run:
# modprobe ecryptfs # ecryptfs-migrate-home -u username
and follow the instructions. After the wrapper script is complete, follow the instructions for auto-mounting - see #Auto-mounting below. It is imperative that the user logs in before the next reboot, to complete the process.
Once everything is working, the unencrypted backup of the users home directory, which is saved to
/home/username.random_characters, can and should be deleted.
Executing the wrapper
and entering the passphrase is all needed to mount the encrypted directory to the above described upper directory
will unmount it again.
The tools include another script that can be very handy to access an encrypted
.Private data or home directory. Executing
ecryptfs-recover-private as root will search the system (or an optional specific path) for the directory, interactively query the passphrase for it and mount the directory. It can, for example, be used from a live-CD or different system to access the encrypted data in case of a recovery. Note that if booting from an Arch Linux ISO you must first install the to it. Further, it will only be able to mount
.Private directories created with the Ubuntu tools.
The default way to auto-mount an encrypted directory is via PAM. See
man pam_ecryptfs and - for more details - 'PAM MODULE' in:
For auto-mounting it is required that the passphrase to access the encrypted directory is synchronised with the user log-in.
The following steps set it up:
1. Check if
~/.ecryptfs/wrapped-passphrase exist (these are automatically created by ecryptfs-setup-private).
2. Add ecryptfs to the pam-stack exactly as following to allow transparent unwrapping of the passphrase on login:
/etc/pam.d/system-auth and after the line containing
auth required pam_unix.so add:
auth required pam_ecryptfs.so unwrap
Next, above the line containing
password required pam_unix.so insert:
password optional pam_ecryptfs.so
And finally, after the line
session required pam_unix.so add:
session optional pam_ecryptfs.so unwrap
3. Re-login and check output of mount which should now contain a mountpoint, e.g.:
/home/$USER/.Private on /home/$USER/Private type ecryptfs (...)
for the user's encrypted directory. It should be perfectly readable at
The latter should be automatically unmounted and made unavailable when the user logs off.
Use ecryptfs-simple if you just want to use eCryptfs to mount arbitrary directories the way you can with EncFS. ecryptfs-simple does not require root privileges or entries in
/etc/fstab, nor is it limited to hard-coded directories such as
~/.Private. The package is available to be installed as AUR and from Xyne's repos.
As the name implies, usage is simple:
# simple mounting ecryptfs-simple /path/to/foo /path/to/bar
# automatic mounting: prompts for options on the first mount of a directory then reloads them next time ecryptfs-simple -a /path/to/foo /path/to/bar
# unmounting by source directory ecryptfs-simple -u /path/to/foo
# unmounting by mountpoint ecryptfs-simple -u /path/to/bar
The following details instructions to set up eCryptfs encrypted directories manually. This involves two steps. First, the passphrase is processed and loaded into the kernel keyring. Second, the filesystem is actually mounted using the key from the keyring.
There are two ways to add the passphrase to the kernel keyring in the first step. The simpler option is
ecryptfs-add-passphrase, which uses a single passphrase to encrypt the files. The disadvantage is that you cannot change the passphrase later. It works like this:
$ ecryptfs-add-passphrase Passphrase: Inserted auth tok with sig [78c6f0645fe62da0] into the user session keyring
You can also pipe a passphrase into
ecryptfs-add-passphrase -. Keep in mind that if you leave your passphrase in a file, it will usually defeat the purpose of using encryption.
As an alternative to a plain passphrase, you can use a "wrapped passphrase", where the files are encrypted using a randomly generated key, which is itself encrypted with your passphrase and stored in a file. In this case, you can change your passphrase by unwrapping the key file with your old passphrase and rewrapping it using your new passphrase.
In the following we do a generation similar to the source and then use ecryptfs-wrap-passphrase to wrap it with the password ("Arch") to
$ printf "%s\n%s" $(od -x -N 100 --width=30 /dev/random | head -n 1 | sed "s/^0000000//" | sed "s/\s*//g") "Arch" | ecryptfs-wrap-passphrase /home/username/.ecryptfs/wrapped-passphrase
Next, we can enter our passphrase "Arch" to load the key into the keyring:
$ printf "%s" "Arch" | ecryptfs-insert-wrapped-passphrase-into-keyring /home/username/.ecryptfs/wrapped-passphrase - Inserted auth tok with sig [7c5d3dd8a1b49db0] into the user session keyring
In either case, when you successfully add the passphrase to the kernel keyring, you will get a "key signature" like
78c6f0645fe62da0 which you will need in the next step.
There are two different ways of manually mounting eCryptfs, described in the following sections. The first way, using
mount.ecryptfs_private, can be run as a regular user and involves setting up some configuration files. This method does not allow you to change the encryption settings, such as key size. The second way is to use a raw
mount command, which gives you complete control over all settings, but requires you to either run it as root, or add an entry to
/etc/fstab which lets a user mount eCryptfs.
With configuration files
This method involves running
mount.ecryptfs_private from the package, after first loading your passphrase. This binary requires no root privileges to work by default.
First choose a name for your configuration files in
~/.ecryptfs and decide on the lower and upper directories. In this example we use
secret for the configuration files, put in encrypted data in
~/.secret, and mount the decrypted files at
~/secret. Create the required directories:
$ mkdir ~/.secret ~/secret ~/.ecryptfs
Now specify the directories in
~/.ecryptfs/secret.conf, using full paths. Its format looks like the one in
/etc/fstab without the mount options:
$ echo "$HOME/.secret $HOME/secret ecryptfs" > ~/.ecryptfs/secret.conf
Write the key signature you got from
ecryptfs-insert-wrapped-passphrase-into-keyring (see above) into
$ echo 78c6f0645fe62da0 > ~/.ecryptfs/secret.sig
If you also want to enable filename encryption, add a second passphrase to the keyring (or reuse the first passphrase) and append its key signature to
$ echo 326a6d3e2a5d444a >> ~/.ecryptfs/secret.sig
$ mount.ecryptfs_private secret
When you're done, unmount it:
$ umount.ecryptfs_private secret
Raw mount command
By running the actual
mount command manually, you get complete control over the encryption options. The disadvantage is that you need to either run
mount as root, or add an entry to
/etc/fstab for each eCryptfs directory so users can mount them.
First create your private directories. In this example, we use the same ones as the previous section:
$ mkdir -m 700 ~/.secret $ mkdir -m 500 ~/secret
- Actual encrypted data will be stored in the lower
- While mounted, decrypted data will be available in
- While not mounted nothing can be written to this directory
- While mounted it has the same permissions as the lower directory
Now, supposed you have created the wrapped keyphrase above, you need to insert the encryption key once to the root user's keyring:
# printf "%s" "Arch" | ecryptfs-insert-wrapped-passphrase-into-keyring /home/username/.ecryptfs/wrapped-passphrase - Inserted auth tok with sig [7c5d3dd8a1b49db0] into the user session keyring
so that the followng mount command succeeds:
# mount -i -t ecryptfs ~/.secret ~/secret -o ecryptfs_sig=7c5d3dd8a1b49db0,ecryptfs_fnek_sig=7c5d3dd8a1b49db0,ecryptfs_cipher=aes,ecryptfs_key_bytes=32,ecryptfs_unlink_sigs
ecryptfs_sigsets the data passphrase key signature.
ecryptfs_fnek_sigsets the filename passphrase key signature; you can omit this option if you do not want to encrypt filenames.
ecryptfs_key_bytescan be 16, 24, or 32 to change the encryption key size.
ecryptfs_unlink_sigswill remove the passphrase(s) from the keyring when you unmount, so you have to add the passphrase(s) back again in order to re-mount the filesystem.
- There are a few other options listed in the
Once you've chosen the right mount options, you can add an entry to
/etc/fstab so regular users can mount eCryptfs on these directories. Copy the mount options to a new
/etc/fstab entry and add the options
noauto. The full entry will look similar to (bold entries added):
/home/username/.secret /home/username/secret ecryptfs noauto,user,ecryptfs_sig=7c5d3dd8a1b49db0,ecryptfs_fnek_sig=7c5d3dd8a1b49db0,ecryptfs_cipher=aes,ecryptfs_key_bytes=32,ecryptfs_unlink_sigs 0 0
noautooption is important, because otherwise systemd will error trying to mount the entry directly on boot.
useroption enables to mount the directory as a user.
- The user mount will default to option
noexec. If you want to have at least executable files in your private directory, you can add
execto the fstab options.
- The user mount will default to option
The setup is now complete and the directory should be mountable by the user.
To mount the encrypted directory as the user, the passphrase must be unwrapped and made available in the user's keyring. Following above section example:
$ ecryptfs-insert-wrapped-passphrase-into-keyring /home/username/.ecryptfs/wrapped-passphrase Passphrase: Inserted auth tok with sig [7c5d3dd8a1b49db0] into the user session keyring
Now the directory can be mounted without the mount helper questions:
$ mount -i /home/username/secret
and files be placed into the
secret directory. The above two steps are necessary every time to mount the directory manually.
To unmount it again:
$ umount /home/username/secret
To finalize, the preliminary passphrase to wrap the encryption passphrase may be changed:
$ ecryptfs-rewrap-passphrase /home/username/.ecryptfs/wrapped-passphrase Old wrapping passphrase: New wrapping passphrase: New wrapping passphrase (again):
The un-mounting should also clear the keyring, to check the user's keyring or clear it manually:
$ keyctl list @u $ keyctl clear @u
Different methods can be employed to automount the previously defined user-mount in
/etc/fstab on login. As a first general step, follow point (1) and (2) of #Auto-mounting.
Another method is to automount the eCryptfs directory on user login using pam_mount. To configure this method, add the following lines to
<luserconf name=".pam_mount.conf.xml" /> <mntoptions require="" /> <lclmount>mount -i %(VOLUME) "%(before=\"-o\" OPTIONS)"</lclmount>
Please prefer writing manually these lines instead of simply copy/pasting them (especially the lclmount line), otherwise you might get some corrupted characters. Explanation:
- the first line indicates where the user-based configuration file is located (here
- the second line overwrites the default required mount options which are unnecessary ("nosuid,nodev")
- the last line indicates which mount command to run (eCryptfs needs the
Then set the volume definition, preferably to
<pam_mount> <volume noroot="1" fstype="ecryptfs" path="/home/user/.secret/" mountpoint="/home/user/secret/"/> </pam_mount>
"noroot" is needed because the encryption key will be added to the user's keyring.
/etc/pam.d/login as described in the pam_mount article.
To avoid wasting time needlessly unwrapping the passphrase you can create a script that will check pmvarrun to see the number of open sessions:
#!/bin/sh # # /usr/local/bin/doecryptfs exit $(/usr/sbin/pmvarrun -u$PAM_USER -o0)
With the following line added before the eCryptfs unwrap module in your PAM stack:
auth [success=ignore default=1] pam_exec.so quiet /usr/local/bin/doecryptfs auth required pam_ecryptfs.so unwrap
The article suggests adding these to
/etc/pam.d/login, but the changes will need to be added to all other places you login, such as
Besides using your private directory as storage for sensitive files, and private data, you can also use it to protect application data. Firefox for example has an internal password manager, but the browsing history and cache can also be sensitive. Protecting it is easy:
$ mv ~/.mozilla ~/Private/mozilla $ ln -s ~/Private/mozilla ~/.mozilla
Removal of encryption
There are no special steps involved, if you want to remove your private directory. Make sure it is un-mounted and delete the respective lower directory (e.g.
~/.Private), along with all the encrypted files. After also removing the related encryption signatures and configuration in
~/.ecryptfs, all is gone.
$ ecryptfs-setup-private --undo
and follow the instructions.
If you want to move a file out of the private directory just move it to the new destination while
~/Private is mounted.
With eCryptfs the cryptographic metadata is stored in the header of the files. Setup variants explained in this article separate the directory with encrypted data from the mount point. The unencrypted mount point is fully transparent and available for a backup. Obviously this has to be considered for automated backups, if one has to avoid leaking sensitive unencrypted data into a backup.
You can do backups, or incremental backups, of the encrypted (e.g.
~/.Private) directory, treating it like any other directory.
Further points to note:
- If you used the Ubuntu tools for #Encrypting a home directory, be aware the location of the lower directory with the encrypted files is outside the regular user's
- It should be ensured to include the eCryptfs setup files (located in
~/.ecryptfsusually) into the regular or a separate backup.
- If you use special filesystem mount options, for example
ecryptfs_xattr, do extra checks on restore integrity.
- eCryptfs - Manpages and project home
- Security audit of eCryptfs by Taylor Hornby (January 22, 2014).
- eCryptfs and $HOME by Adrian C. (anrxc) - Article with installation instructions and discussion of eCryptfs usage
- Chromium data protection (November 2009) - Design document detailing encryption options for Chromium OS, including explanation on its eCryptfs usage
- eCryptfs design by Michael Halcrow (May 2005) - Original design document detailing and discussing eCryptfs