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* Manual fixes.

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Eelco Dolstra 2004-11-14 00:24:57 +00:00
parent 54c7a870d5
commit 0b79a12082
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40
doc/manual/introduction.xml
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@ -12,11 +12,11 @@ features are:
<itemizedlist>
<listitem><para>It makes sure that dependency specifications are
complete. In general in a deployment system you have to specify for
each component what its dependencies are, but there are no guarantees
that this specification is complete. If you forget a dependency, then
the component will build and work correctly on
<listitem><para>It helps you make sure that dependency specifications
are complete. In general in a deployment system you have to specify
for each component what its dependencies are, but there are no
guarantees that this specification is complete. If you forget a
dependency, then the component will build and work correctly on
<emphasis>your</emphasis> machine if you have the dependency
installed, but not on the end user's machine if it's not
there.</para></listitem>
@ -25,8 +25,8 @@ there.</para></listitem>
variants</emphasis> of a component installed at the same time. In
contrast, in systems such as RPM different versions of the same
package tend to install to the same location in the file system, so
you installing one version will remove the other. This is especially
important if you want to have use applications that have conflicting
installing one version will remove the other. This is especially
important if you want to use applications that have conflicting
requirements on different versions of a component (e.g., application A
requires version 1.0 of library X, while application B requires a
non-backwards compatible version 1.1).</para></listitem>
@ -45,24 +45,23 @@ component to fail).</para></listitem>
<listitem><para>Likewise, it is possible to atomically roll back after
an install, upgrade, or uninstall action. That is, in a fast (O(1))
operation the previous configuration of the system will be restored.
This is because upgrade or uninstall actions doesn't actually remove
operation the previous configuration of the system can be restored.
This is because upgrade or uninstall actions don't actually remove
components from the system.</para></listitem>
<listitem><para>Unused components can be
<emphasis>garbage-collected</emphasis> automatically and safely.
I.e., when you remove an application from a profile, its dependencies
will be deleted by the garbage collector if there are no other active
applications that are using it.</para></listitem>
<emphasis>garbage-collected</emphasis> automatically and safely: when
you remove an application from a profile, its dependencies will be
deleted by the garbage collector only if there are no other active
applications using them.</para></listitem>
<listitem><para>Nix supports both source-based deployment models
(where you distribute <emphasis>Nix expressions</emphasis> that tell
Nix how to build software from source) and binary-based deployment
models. The latter is more-or-less transparent: installation of
components is always based on Nix expressions, but if those
expressions have been built before and Nix knows that the resulting
binaries are available somewhere, it will use those
instead.</para></listitem>
components is always based on Nix expressions, but if the expressions
have been built before and Nix knows that the resulting binaries are
available somewhere, it will use those instead.</para></listitem>
<listitem><para>Nix is flexible in the deployment policies that it
supports. There is a clear separation between the tools that
@ -80,13 +79,12 @@ This means that if a component was built succesfully once, it can be
rebuilt again on another machine and the result will be the same. We
cannot <emphasis>guarantee</emphasis> this (e.g., if the build depends
on the time-of-day), but Nix (and the tools in the Nix Packages
collection) takes special measures to help achieve
this.</para></listitem>
collection) takes special care to help achieve this.</para></listitem>
<listitem><para>Nix expressions (the things that tell Nix how to build
components) are self-contained: they describe not just components but
complete compositions. In other words, Nix expressions also describe
how to build all the dependencies. This is contrast to component
how to build all the dependencies. This is in contrast to component
specification languages like RPM spec files, which might say that a
component X depends on some other component Y, but since it does not
describe <emphasis>exactly</emphasis> what Y is, the result of
@ -111,7 +109,7 @@ platforms.</para></listitem>
also for <emphasis>service deployment</emphasis>, such as the
deployment of a complete web server with all its configuration files,
static pages, software dependencies, and so on. Nix's advantages for
software deployment also apply here, for instance, the ability
software deployment also apply here: for instance, the ability
trivially to have multiple configurations at the same time, or the
ability to do rollbacks.</para></listitem>