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* Started on the introduction.
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Eelco Dolstra
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<chapter>
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<title>Introduction</title>
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<para>
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Nix is a system for the automatic creation and distribution of data, such
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as computer programs and other software artifacts.
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</para>
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<sect1>
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<title>The problem space</title>
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<para>
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Nix is a system for controlling the automatic creation and distribution
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of data, such as computer programs and other software artifacts. This
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is a very general problem, and there are many applications that fall
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under this description.
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</para>
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<sect2>
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<title>Build management</title>
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<para>
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Build management tools are used to perform <emphasis>software
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builds</emphasis>, that is, the construction of derived products
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such as executable programs from source code. A commonly used build
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tool is Make, which is a standard tool on Unix systems. These tools
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have to deal with several issues:
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<itemizedlist>
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<listitem>
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<para>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</sect2>
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<sect2>
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<title>Package management</title>
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<para>
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After software has been built, is must also be
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<emphasis>deployed</emphasis> in the intended target environment,
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e.g., the user's workstation. Examples include the Red Hat package
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manager (RPM), Microsoft's MSI, and so on. Here also we have to deal
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with several issues:
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<itemizedlist>
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<listitem>
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<para>
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The <emphasis>creation</emphasis> of packages from some formal
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description of what artifacts should be distributed in the
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package.
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</para>
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</listitem>
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<listitem>
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<para>
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The <emphasis>deployment</emphasis> of packages, that is, the
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mechanism by which we get them onto the intended target
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environment. This can be as simple as copying a file, but
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complexity comes from the wide range of possible installation
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media (such as a network install), and the scalability of the
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process (if a program must be installed on a thousand systems,
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we do not want to visit each system and perform some manual
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steps to install the program on that system; that is, the
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complexity for the system administrator should be constant, not
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linear).
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</sect2>
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</sect1>
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<sect1>
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<title>The Nix system</title>
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<para>
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...
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</para>
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<para>
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Existing tools in this field generally both a underlying model (such as
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the derivation graph of build tools, or the versioning scheme that
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determines when two packages are <quote>compatible</quote> in a package
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management system) and a formalism that allows ...
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</para>
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<para>
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Following the principle of separation of mechanism and policy, the Nix
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system separates the <emphasis>low-level aspect</emphasis> of file
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system object management form the <emphasis>high-level
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aspect</emphasis> of the ...
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</para>
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</sect1>
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</chapter>
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<!--======================================================================-->
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<chapter>
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<title>A Guided Tour</title>
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<para>
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Bla bla
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</para>
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</chapter>
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<!--======================================================================-->
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<chapter>
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<title>Fix Language Reference</title>
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<para>
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Bla bla
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</para>
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</chapter>
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<!--======================================================================-->
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<chapter>
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<title>Nix Syntax and Semantics</title>
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<para>
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Bla bla
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</para>
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</chapter>
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@ -99,4 +216,74 @@ $ make install</screen>
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</chapter>
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<!--======================================================================-->
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<appendix>
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<title>Troubleshooting</title>
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<sect1>
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<title>Database hangs</title>
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<para>
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If Nix or Fix appear to hang immediately after they are started, Nix's
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database is probably <quote>wedged</quote>, i.e., some process died
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while it held a lock on the database. The solution is to ensure that
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no other processes are accessing the database and then run the
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following command:
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</para>
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<screen>
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$ db_recover -e -h <replaceable>prefix</replaceable>/var/nix/db</screen>
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<para>
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Here, <replaceable>prefix</replaceable> should be replaced by Nix's
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installation prefix.
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</para>
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</sect1>
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<sect1>
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<title>Database logfile removal</title>
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<para>
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Every time a Nix database transaction takes place, Nix writes a record
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of this transaction to a <emphasis>log</emphasis> in its database
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directory to ensure that the operation can be replayed in case of a
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application or system crash. However, without manual intervention,
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the log grows indefinitely. Hence, unused log files should be deleted
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periodically. This can be accomplished using the following command:
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</para>
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<screen>
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$ rm `db_archive -a -h <replaceable>prefix</replaceable>/var/nix/db`</screen>
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</sect1>
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</appendix>
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<!--======================================================================-->
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<appendix>
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<title>Known problems</title>
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<itemizedlist>
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<listitem>
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<para>
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Nix should automatically recover the Berkeley DB database.
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</para>
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</listitem>
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<listitem>
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<para>
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Nix should automatically remove Berkeley DB logfiles.
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</para>
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</listitem>
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</itemizedlist>
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</appendix>
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</book>
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