Why?
How?

Why?

The Debian mirrors live-build uses are very much configurable (see custom mirror), but Tails uses some non-Debian APT repositories whose location cannot be adapted to your build environment using only live-build settings.

Moreover, some packages fetch data online over HTTP at install time i.e. at Tails build time.

Both of these factors make it hard to build Tails offline... unless you have a HTTP proxy with all necessary files cached on disk, that is able to switch to offline mode.

How?

Install and configure squid-deb-proxy

squid-deb-proxy is a Debian proxy solution based on Squid with a tweaked configuration. It has a homepage on Launchpad and packages in Ubuntu.

On the other hand, we've found the upstream and Ubuntu packages to require many changes to be usable in Debian and especially for Tails purposes. Until we manage to turn our changes into a proper Debian package and make them generic enough to be pushed upstream, we recommend using the installation instructions bellow.

Install necessary dependencies:
```
    apt-get install squid3
```

Create the necessary directories:

    install -o root  -g root -m 00755 -d /etc/squid-deb-proxy
    install -o proxy -g root -m 00750 -d /var/cache/squid-deb-proxy
    install -o proxy -g root -m 00750 -d /var/log/squid-deb-proxy

Install the attached configuration files; all shall be owned by root:root and have 00644 permissions unless otherwise noted:
/etc/squid-deb-proxy/squid-deb-proxy.conf is the main configuration file passed to Squid3.
/etc/squid-deb-proxy/allowed-networks-src.acl lists the network sources that are allowed to access the cache
/etc/squid-deb-proxy/mirror-dstdomain.acl lists the network destinations the proxy is allowed to reach
/etc/init.d/squid-deb-proxy is the initscript; it needs to be made executable.
Adapt the configuration for your needs:
The example cache_mem setting shall be changed depending on the amount of RAM your build machine has
The example cache_dir has a 10G limit that is a bit high if you only want to use squid-deb-proxy to build Tails.

Have the proxy start on boot:

    update-rc.d squid-deb-proxy defaults

Start the proxy:
```
    invoke-rc.d squid-deb-proxy start
```

Use the proxy for live-build and APT

You need to set a few options in live-build's configuration file (/etc/live/build.conf).

First, the following line asks live-build to use the configured proxy for any use of APT it makes:

LB_APT_HTTP_PROXY="http://127.0.0.1:8000/"

Second, you probably need to ask live-build to use a custom Debian mirror to fit the destination domain restrictions you set previously up.

Use the proxy for non-APT purposes

Export the http_proxy='http://127.0.0.1:8000/' environment variable in the (root) shell you want to run the build in. This way, HTTP requests that are made by anyone else than APT during the build will use the configured Squid proxy.

Build offline

Un-comment the settings in the Offline mode section at the end of /etc/squid-deb-proxy/squid-deb-proxy.conf.