Building a Tails image
Download Tails 1.0.1 June 10, 2014
  1. Using Vagrant
    1. Local HTTP proxy
    2. Build options
  2. Building manually
    1. Dependencies
    2. Configure live-build
    3. Build process
  3. More information
  4. Related pages

Using Vagrant

Tails can be built easily in a virtual machine using Rake, Vagrant and VirtualBox. The process requires a minimum of 1 GB of free memory and a maximum of 10 GB of free storage.

Installing the needed tools on Debian Wheezy is a matter of:

$ sudo apt-get install virtualbox vagrant rake

Then, please run:

$ git clone git://git.tails.boum.org/tails
$ cd tails
$ git checkout devel
$ export TAILS_BUILD_OPTIONS="noproxy"
$ rake build
$ unset TAILS_BUILD_OPTIONS

The first time, this can take a little while to download the base virtual machine from Tails mirror (around 300 MB). It will then boot the machine, set it up and start the build process. When done, several tails-* files should appear in the current directory.

After you are done working on Tails, do not forget to shut the virtual machine down:

$ rake vm:halt

One may also want to customize their image before building.

To know all available Rake tasks, please run rake -T.

Local HTTP proxy

If you have a local HTTP proxy, the build system will use it as long as you properly set the http_proxy environment variable. The easiest way to do so is to run:

$ export http_proxy=http://proxy.lan:3142

This needs to be done before any other operations.

Build options

Options regarding the build process can be set using the TAILS_BUILD_OPTIONS environment variable. Muliple options must be separated by whitespaces.

The following options are available:

Memory build settings

Tails builds way faster when everything is done in memory. If your computer runs Linux and happens to have more than 6.5 GB of free memory before you start the virtual machine, it will automatically switch to 'build in RAM' mode.

To force a specific behaviour please set:

  • ram: start the virtual machine with 6.5GB of memory, build Tails inside a tmpfs. Build fails if the system is not in a proper state to do so.
  • noram: start the virtual machine with 1GB of memory if not already done, build Tails using the virtual machine hard disk.

HTTP proxy settings

Building Tails requires downloading a little bit more than 1 GB of Debian packages. To preserve bandwidth and developer sanity, using a HTTP proxy is nearly a must. Tails virtual machine contains a fully configured local HTTP proxy that will be used if no other local proxy is defined.

The following flags can be used to force a specific behaviour:

  • extproxy: use the proxy configured through the http_proxy environment variable. Fail if it is not set.
  • vmproxy: use the local proxy configured in the virtual machine even if a local HTTP proxy is set.
  • noproxy: do not use any HTTP proxy.

Bootstrap cache settings

A Tails build starts with debootstrap:ing a minimal Debian system which then is modified into a full Tails system. This is a rather time consuming step that usually does not have to be done: the packages used in it rarely get updated and hence the result is exactly the same most of the time.

The following flags can be used to force a specific behaviour:

  • cache: re-use a cached bootstrap stage (if available), and saves the bootstrap stage to disk on successful build. This will also reduce the amount of memory required for in-memory builds by around 150 MiB (see the ram option above). Warning: this option may create subtle differences between builds from the exact same Tails source which are hard to track to track and understand. Use this option only if you know what you are doing, and if you are not building an actual release.
  • nocache: do the bootstrap stage from scratch (default).

SquashFS compression settings

One of the most expensive operations when building Tails is the creation of the final SquashFS. It also depends on the compression algorithm used. When working on the stable or testing branch, the image will be made using the slow but efficient default. Any other setup will switch to the faster gzip.

Forcing a specific behaviour can be done using:

  • gzipcomp: always use gzip to create the SquashFS.
  • defaultcomp: always use the default compression algorithm.

Clean-up settings

Some operations are preserved accross builds. Currently they are:

  • The wiki (for documentation).
  • The bootstrap stage cache (see the cache option above).

In case you want to delete all these, the following option is available:

  • cleanall: force a clean up before starting the build.

Virtual CPUs settings

The number of virtual CPUs that are allocated in the virtual machine can be set through:

  • cpus=n: allocate n CPUs to the virtual machine.

Obviously you should not allocate more virtual CPUs than the number of cores available to the host system. When using Linux, the number of CPUs allocated will default to be the same as the host system.

Git settings

The build system can only work on files that have been commited to the Git repository. By default, it will refuse to start a build in presence of uncommited changes. This behaviour can be controlled by:

  • ignorechanges: allow to make a build that will ignore changes in the Git repository.

Example

The fastest build you could pretend to get can be done by setting:

export TAILS_BUILD_OPTIONS="ram cache extproxy gzipcomp"

This will force the build to happen in RAM and allow skipping the boostrap stage if one is cached, and will use use an HTTP proxy external to the virtual machine, and SquashFS compression will be done using gzip.

Building manually

In order to build Tails manually, you need a running Debian Wheezy system and some backports. Anything else will fail.

Dependencies

The following Debian packages need to be installed:

  • our live-build 2.x package, adapted for Wheezy. Its version is something like 3.0.5+really+is+2.0.12-0.tails1. One can install it from:

    deb http://deb.tails.boum.org/ builder-wheezy main

    This APT repository's signing key can be found on the keyservers. It is certified by the Tails signing key, and its fingerprint is:

    221F 9A3C 6FA3 E09E 182E  060B C798 8EA7 A358 D82E

  • syslinux

  • eatmydata, time and whois (for /usr/bin/mkpasswd)
  • ikiwiki 3.20120725 or newer, available in wheezy-backports.
  • apt-get install libyaml-perl libyaml-libyaml-perl po4a perlmagick libyaml-syck-perl so that the wiki builds smoothly.
  • dpkg-dev
  • intltool

Configure live-build

Add these lines to /etc/live/build.conf:

LB_PARENT_MIRROR_BINARY="http://ftp.us.debian.org/debian/"
LB_MIRROR_BINARY="http://ftp.us.debian.org/debian/"

Build process

Every build command must be run as root, at the root of a clone of the tails repository.

In short, a build could be done using:

# lb clean --all && lb config && lb build

Customize the build process if needed

If you need to set custom build settings that are specific to your local environment, such as a custom Debian mirror or APT proxy, you probably want to configure live-build a bit.

The most common customizations are documented on this wiki:

More documentation about this can be found in the Debian Live Manual.

Initialize the Live system's configuration

Initialize the Live system's configuration with lb config in a clean build tree. Most lb config options are supported, have a look to the lb_config(1) manpage for details.

Build the system

You can then use the standard live-build commands as root to build the image (lb build) and to cleanup the build directory (lb clean).

More information

More documentation about the build process can be found in the Debian Live Manual.

Related pages