Using APT Offline


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                               Jason Gunthorpe

                              <jgg@debian.org>

                                Version 1.4.6

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Copyright © 1999 Jason Gunthorpe

License Notice

    "APT" and this document are free software; you can redistribute them and/
    or modify them under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.

    For more details, on Debian systems, see the file /usr/share/
    common-licenses/GPL for the full license.

Abstract

This document describes how to use APT in a non-networked environment,
specifically a 'sneaker-net' approach for performing upgrades.

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Table of Contents

1. Introduction

    1.1. Overview

2. Using APT on both machines

    2.1. Overview
    2.2. The configuration file

3. Using APT and wget

    3.1. Overview
    3.2. Operation

Chapter 1. Introduction

Table of Contents

1.1. Overview

1.1. Overview

    Normally APT requires direct access to a Debian archive, either from a
    local media or through a network. Another common complaint is that a
    Debian machine is on a slow link, such as a modem and another machine has
    a very fast connection but they are physically distant.

    The solution to this is to use large removable media such as a Zip disc
    or a SuperDisk disc. These discs are not large enough to store the entire
    Debian archive but can easily fit a subset large enough for most users.
    The idea is to use APT to generate a list of packages that are required
    and then fetch them onto the disc using another machine with good
    connectivity. It is even possible to use another Debian machine with APT
    or to use a completely different OS and a download tool like wget. Let 
    remote host mean the machine downloading the packages, and target host
    the one with bad or no connection.

    This is achieved by creatively manipulating the APT configuration file.
    The essential premise to tell APT to look on a disc for it's archive
    files. Note that the disc should be formatted with a filesystem that can
    handle long file names such as ext2, fat32 or vfat.

Chapter 2. Using APT on both machines

Table of Contents

2.1. Overview
2.2. The configuration file

2.1. Overview

    APT being available on both machines gives the simplest configuration.
    The basic idea is to place a copy of the status file on the disc and use
    the remote machine to fetch the latest package files and decide which
    packages to download. The disk directory structure should look like:

      /disc/
        archives/
           partial/
        lists/
           partial/
        status
        sources.list
        apt.conf

2.2. The configuration file

    The configuration file should tell APT to store its files on the disc and
    to use the configuration files on the disc as well. The sources.list
    should contain the proper sites that you wish to use from the remote
    machine, and the status file should be a copy of /var/lib/dpkg/status
    from the target host. Please note, if you are using a local archive you
    must use copy URIs, the syntax is identical to file URIs.

    apt.conf must contain the necessary information to make APT use the disc:

     APT
     {
       /* This is not necessary if the two machines are the same arch, it tells
          the remote APT what architecture the target machine is */
       Architecture "i386";

       Get::Download-Only "true";
     };

     Dir
     {
       /* Use the disc for state information and redirect the status file from
          the /var/lib/dpkg default */
       State "/disc/";
       State::status "status";

       // Binary caches will be stored locally
       Cache::archives "/disc/archives/";
       Cache "/tmp/";

       // Location of the source list.
       Etc "/disc/";
     };

    More details can be seen by examining the apt.conf man page and the
    sample configuration file in /usr/share/doc/apt/examples/apt.conf.

    On the target machine the first thing to do is mount the disc and copy /
    var/lib/dpkg/status to it. You will also need to create the directories
    outlined in the Overview, archives/partial/ and lists/partial/. Then take
    the disc to the remote machine and configure the sources.list. On the
    remote machine execute the following:

     # export APT_CONFIG="/disc/apt.conf"
     # apt-get update
     [ APT fetches the package files ]
     # apt-get dist-upgrade
     [ APT fetches all the packages needed to upgrade the target machine ]

    The dist-upgrade command can be replaced with any other standard APT
    commands, particularly dselect-upgrade. You can even use an APT front end
    such as dselect. However this presents a problem in communicating your
    selections back to the local computer.

    Now the disc contains all of the index files and archives needed to
    upgrade the target machine. Take the disc back and run:

      # export APT_CONFIG="/disc/apt.conf"
      # apt-get check
      [ APT generates a local copy of the cache files ]
      # apt-get --no-d -o dir::state::status=/var/lib/dpkg/status dist-upgrade
      [ Or any other APT command ]

    It is necessary for proper function to re-specify the status file to be
    the local one. This is very important!

    If you are using dselect you can do the very risky operation of copying
    disc/status to /var/lib/dpkg/status so that any selections you made on
    the remote machine are updated. I highly recommend that people only make
    selections on the local machine - but this may not always be possible. DO
    NOT copy the status file if dpkg or APT have been run in the mean time!!

Chapter 3. Using APT and wget

Table of Contents

3.1. Overview
3.2. Operation

3.1. Overview

    wget is a popular and portable download tool that can run on nearly any
    machine. Unlike the method above this requires that the Debian machine
    already has a list of available packages.

    The basic idea is to create a disc that has only the archive files
    downloaded from the remote site. This is done by using the --print-uris
    option to apt-get and then preparing a wget script to actually fetch the
    packages.

3.2. Operation

    Unlike the previous technique no special configuration files are
    required. We merely use the standard APT commands to generate the file
    list.

     # apt-get dist-upgrade
     [ Press no when prompted, make sure you are happy with the actions ]
     # apt-get -qq --print-uris dist-upgrade > uris
     # awk '{print "wget -O " $2 " " $1}' < uris > /disc/wget-script

    Any command other than dist-upgrade could be used here, including
    dselect-upgrade.

    The /disc/wget-script file will now contain a list of wget commands to
    execute in order to fetch the necessary archives. This script should be
    run with the current directory as the disc's mount point so as to save
    the output on the disc.

    The remote machine would do something like

      # cd /disc
      # sh -x ./wget-script
      [ wait.. ]

    Once the archives are downloaded and the disc returned to the Debian
    machine installation can proceed using,

      # apt-get -o dir::cache::archives="/disc/" dist-upgrade

    Which will use the already fetched archives on the disc.