* Started on the introduction.

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Eelco Dolstra 2003-08-07 15:27:14 +00:00
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<chapter>
<title>Introduction</title>
<para>
Nix is a system for the automatic creation and distribution of data, such
as computer programs and other software artifacts.
</para>
<sect1>
<title>The problem space</title>
<para>
Nix is a system for controlling the automatic creation and distribution
of data, such as computer programs and other software artifacts. This
is a very general problem, and there are many applications that fall
under this description.
</para>
<sect2>
<title>Build management</title>
<para>
Build management tools are used to perform <emphasis>software
builds</emphasis>, that is, the construction of derived products
such as executable programs from source code. A commonly used build
tool is Make, which is a standard tool on Unix systems. These tools
have to deal with several issues:
<itemizedlist>
<listitem>
<para>
</para>
</listitem>
</itemizedlist>
</para>
</sect2>
<sect2>
<title>Package management</title>
<para>
After software has been built, is must also be
<emphasis>deployed</emphasis> in the intended target environment,
e.g., the user's workstation. Examples include the Red Hat package
manager (RPM), Microsoft's MSI, and so on. Here also we have to deal
with several issues:
<itemizedlist>
<listitem>
<para>
The <emphasis>creation</emphasis> of packages from some formal
description of what artifacts should be distributed in the
package.
</para>
</listitem>
<listitem>
<para>
The <emphasis>deployment</emphasis> of packages, that is, the
mechanism by which we get them onto the intended target
environment. This can be as simple as copying a file, but
complexity comes from the wide range of possible installation
media (such as a network install), and the scalability of the
process (if a program must be installed on a thousand systems,
we do not want to visit each system and perform some manual
steps to install the program on that system; that is, the
complexity for the system administrator should be constant, not
linear).
</para>
</listitem>
</itemizedlist>
</para>
</sect2>
</sect1>
<sect1>
<title>The Nix system</title>
<para>
...
</para>
<para>
Existing tools in this field generally both a underlying model (such as
the derivation graph of build tools, or the versioning scheme that
determines when two packages are <quote>compatible</quote> in a package
management system) and a formalism that allows ...
</para>
<para>
Following the principle of separation of mechanism and policy, the Nix
system separates the <emphasis>low-level aspect</emphasis> of file
system object management form the <emphasis>high-level
aspect</emphasis> of the ...
</para>
</sect1>
</chapter>
<!--======================================================================-->
<chapter>
<title>A Guided Tour</title>
<para>
Bla bla
</para>
</chapter>
<!--======================================================================-->
<chapter>
<title>Fix Language Reference</title>
<para>
Bla bla
</para>
</chapter>
<!--======================================================================-->
<chapter>
<title>Nix Syntax and Semantics</title>
<para>
Bla bla
</para>
</chapter>
@ -99,4 +216,74 @@ $ make install</screen>
</chapter>
<!--======================================================================-->
<appendix>
<title>Troubleshooting</title>
<sect1>
<title>Database hangs</title>
<para>
If Nix or Fix appear to hang immediately after they are started, Nix's
database is probably <quote>wedged</quote>, i.e., some process died
while it held a lock on the database. The solution is to ensure that
no other processes are accessing the database and then run the
following command:
</para>
<screen>
$ db_recover -e -h <replaceable>prefix</replaceable>/var/nix/db</screen>
<para>
Here, <replaceable>prefix</replaceable> should be replaced by Nix's
installation prefix.
</para>
</sect1>
<sect1>
<title>Database logfile removal</title>
<para>
Every time a Nix database transaction takes place, Nix writes a record
of this transaction to a <emphasis>log</emphasis> in its database
directory to ensure that the operation can be replayed in case of a
application or system crash. However, without manual intervention,
the log grows indefinitely. Hence, unused log files should be deleted
periodically. This can be accomplished using the following command:
</para>
<screen>
$ rm `db_archive -a -h <replaceable>prefix</replaceable>/var/nix/db`</screen>
</sect1>
</appendix>
<!--======================================================================-->
<appendix>
<title>Known problems</title>
<itemizedlist>
<listitem>
<para>
Nix should automatically recover the Berkeley DB database.
</para>
</listitem>
<listitem>
<para>
Nix should automatically remove Berkeley DB logfiles.
</para>
</listitem>
</itemizedlist>
</appendix>
</book>