/usr/share/doc/debdelta-doc/html/index.html

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>The debdelta suite</TITLE
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><DIV
CLASS="TITLEPAGE"
><H1
CLASS="title"
><A
NAME="AEN1"
>The debdelta suite</A
></H1
><H3
CLASS="author"
><A
NAME="AEN4"
>Andrea C. G. Mennucci</A
></H3
><P
CLASS="copyright"
>Copyright &copy; 2006-2011 </P
><DIV
><DIV
CLASS="abstract"
><P
></P
><A
NAME="AEN8"
></A
><P
>debdelta is an application suite designed to compute
    changes between Debian packages. These changes (that we will call
    'deltas') are similar to the output of the "diff" program in that
    they may be used to store and transmit only the changes between
    Debian packages.  This suite contains 'debdelta-upgrade', that
    downloads deltas and use them to create all Debian packages needed
    for an 'apt-get upgrade'.  </P
><P
></P
></DIV
></DIV
><HR></DIV
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>1. <A
HREF="index.html#AEN13"
>Overview</A
></DT
><DD
><DL
><DT
>1.1. <A
HREF="index.html#AEN16"
>debdelta</A
></DT
><DT
>1.2. <A
HREF="index.html#AEN21"
>debpatch</A
></DT
><DT
>1.3. <A
HREF="index.html#AEN27"
>debdeltas</A
></DT
><DT
>1.4. <A
HREF="index.html#AEN34"
>debdelta-upgrade</A
></DT
><DT
>1.5. <A
HREF="index.html#AEN43"
>debforensic</A
></DT
></DL
></DD
><DT
>2. <A
HREF="x54.html"
>a delta</A
></DT
><DD
><DL
><DT
>2.1. <A
HREF="x54.html#AEN58"
>the info in a delta</A
></DT
><DT
>2.2. <A
HREF="x54.html#AEN61"
>how to apply a delta</A
></DT
></DL
></DD
><DT
>3. <A
HREF="x65.html"
>debdelta-upgrade service</A
></DT
><DD
><DL
><DT
>3.1. <A
HREF="x65.html#AEN69"
>The framework</A
></DT
><DT
>3.2. <A
HREF="x65.html#AEN74"
>The goals</A
></DT
><DT
>3.3. <A
HREF="x65.html#AEN82"
>The repository structure</A
></DT
><DT
>3.4. <A
HREF="x65.html#delta_creation"
>The repository creation</A
></DT
><DT
>3.5. <A
HREF="x65.html#AEN102"
>size limit</A
></DT
><DT
>3.6. <A
HREF="x65.html#AEN106"
>/etc/debdelta/sources.conf</A
></DT
><DT
>3.7. <A
HREF="x65.html#AEN115"
>indexes</A
></DT
><DD
><DL
><DT
>3.7.1. <A
HREF="x65.html#AEN117"
>indexes of debs in APT</A
></DT
><DT
>3.7.2. <A
HREF="x65.html#no_indexes"
>no indexes of deltas in debdelta</A
></DT
></DL
></DD
><DT
>3.8. <A
HREF="x65.html#no_incremental"
>no incremental deltas</A
></DT
><DD
><DL
><DT
>3.8.1. <A
HREF="x65.html#AEN131"
>What "incremental" would be, and why it is not</A
></DT
></DL
></DD
><DT
>3.9. <A
HREF="x65.html#repo_howto"
>Repository howto</A
></DT
><DD
><DL
><DT
>3.9.1. <A
HREF="x65.html#AEN154"
>debmirror --debmarshal</A
></DT
><DT
>3.9.2. <A
HREF="x65.html#AEN167"
>hooks and repository of old_debs</A
></DT
></DL
></DD
></DL
></DD
><DT
>4. <A
HREF="x182.html"
>Goals, tricks, ideas and issues</A
></DT
><DD
><DL
><DT
>4.1. <A
HREF="x182.html#AEN184"
>exact patching</A
></DT
><DT
>4.2. <A
HREF="x182.html#AEN195"
>exact recompression</A
></DT
><DT
>4.3. <A
HREF="x182.html#AEN204"
>speed</A
></DT
><DD
><DL
><DT
>4.3.1. <A
HREF="x182.html#AEN206"
>some (old) numbers</A
></DT
><DT
>4.3.2. <A
HREF="x182.html#AEN212"
>speeding up</A
></DT
><DT
>4.3.3. <A
HREF="x182.html#AEN216"
>the 10kb trick</A
></DT
><DT
>4.3.4. <A
HREF="x182.html#predictor"
>the choice, the predictor</A
></DT
><DT
>4.3.5. <A
HREF="x182.html#AEN232"
>State of the art</A
></DT
></DL
></DD
><DT
>4.4. <A
HREF="x182.html#the_enemy_within"
>better deb compression is a worse delta</A
></DT
><DT
>4.5. <A
HREF="x182.html#long_time"
>long time recovery</A
></DT
><DT
>4.6. <A
HREF="x182.html#AEN249"
>streaming</A
></DT
><DT
>4.7. <A
HREF="x182.html#format_unzipped"
>--format=unzipped</A
></DT
><DT
>4.8. <A
HREF="x182.html#format_preunpacked"
>--format=preunpacked</A
></DT
></DL
></DD
><DT
>5. <A
HREF="x277.html"
>Todo</A
></DT
><DD
><DL
><DT
>5.1. <A
HREF="x277.html#AEN279"
>todo list</A
></DT
><DT
>5.2. <A
HREF="x277.html#getting_worse"
>things are getting worse</A
></DT
></DL
></DD
></DL
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="AEN13"
>1. Overview</A
></H1
><P
>&#13;      The debdelta application suite is really composed of different
    applications.</P
><DIV
CLASS="section"
><H2
CLASS="section"
><A
NAME="AEN16"
>1.1. debdelta</A
></H2
><P
>&#13;      <B
CLASS="command"
>debdelta</B
> computes the delta, that is, a file
      that encodes the difference between two Debian packages.
      
      Example:
      <PRE
CLASS="programlisting"
>&#13;	$ a=/var/cache/apt/archives 
	$ debdelta -v $a/emacs-snapshot-common_1%3a20060512-1_all.deb \
	$a/emacs-snapshot-common_1%3a20060518-1_all.deb /tmp/emacs.debdelta
      </PRE
>
      the result is:
      deb delta is  12.5% of deb ; that is, 15452kB would be saved
    </P
></DIV
><DIV
CLASS="section"
><H2
CLASS="section"
><A
NAME="AEN21"
>1.2. debpatch</A
></H2
><P
>&#13;      <B
CLASS="command"
>debpatch</B
> 
      can use the delta file and a copy of the old Debian package
      to recreate the new Debian package.  (This process is called "applying
      the delta file"). If the old Debian package is not available, but is
      installed in the host, it can use the installed data; in this case,
      '/' is used in lieu of the old .deb.
    </P
><P
>&#13;      Example:
      <PRE
CLASS="programlisting"
>&#13;	$ debpatch -A  /tmp/emacs.debdelta / /tmp/emacs.deb
      </PRE
>
    </P
></DIV
><DIV
CLASS="section"
><H2
CLASS="section"
><A
NAME="AEN27"
>1.3. debdeltas</A
></H2
><P
>&#13;      <B
CLASS="command"
>debdeltas</B
>
      can be used to generate deltas for many debs at once.
      It will generate delta files with names such as
      <TT
CLASS="filename"
>package_old-version_new-version_architecture.debdelta</TT
>.
      
      If the delta exceeds ~70% of the deb, 'debdeltas' will delete it
      and leave a stamp of the form
      <TT
CLASS="filename"
>package_old-version_new-version_architecture.debdelta-too-big</TT
>.

      Example usages are in the man page; see also <A
HREF="x65.html#repo_howto"
>Section 3.9</A
>.
    </P
></DIV
><DIV
CLASS="section"
><H2
CLASS="section"
><A
NAME="AEN34"
>1.4. debdelta-upgrade</A
></H2
><P
>&#13;      <B
CLASS="command"
>debdelta-upgrade</B
>
      will download necessary deltas
      and apply them to create debs for a
      successive  <B
CLASS="command"
>apt-get upgrade</B
>.

      The deltas are available for upgrades in
      'stable' , 'stable-security' , 'testing', 'unstable' and 'experimental',
      for i386 and amd64.

      Example usage:
      <PRE
CLASS="programlisting"
>&#13;	# apt-get update &#38;&#38; debdelta-upgrade &#38;&#38; apt-get upgrade
      </PRE
>
      If run by a non-root user, debs are saved in /tmp/archives : do not
      forget to move them in <TT
CLASS="filename"
>/var/cache/apt/archives</TT
>
    </P
><P
>&#13;      debdelta-upgrade will also download .debs for which no delta is
      available (this is done in parallel to patching, to maximize
      speed). See the explanation of "debdelta-upgrade --deb-policy" in the
      man page for more informations and customization on which debs get downloaded.
    </P
><P
>&#13;      More informations are in next sections.
    </P
></DIV
><DIV
CLASS="section"
><H2
CLASS="section"
><A
NAME="AEN43"
>1.5. debforensic</A
></H2
><P
>&#13;      <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
> There is also another bunch of code 
      (that though was never distributed.... it is available in the GIT repo).
      </I
></SPAN
>. 
      <B
CLASS="command"
>debforensics</B
> creates
      and uses sqlite databases containing information regarding
      debian binary packages. <B
CLASS="command"
>debforensics --add</B
>
      will scan debian packages and add the list of files (and SHA1 hashes
      of them) to the database. <B
CLASS="command"
>debforensics --scan</B
>
      will check a file against multiple databases, to see if that file is part
      of any package.  <B
CLASS="command"
>debforensics --forensic</B
>
      will scan a filesystem and list files that are part of a package, and
      files that are not (or are missplaced, or have strange permissions....).
    </P
><P
>&#13;      If debdelta-upgrade fails to apply a delta, and '-d' is passed,
      then a debug file is generated, and  then debforensic may be used
      to understand what went wrong (theoretically).</P
><DIV
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><P
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><P
>Beware: a full database for main/amd64 is 
       ~350MBs, without indexes. So in practice currently I cannot keep
        a database in my host.</P
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