[ab4fdfc] | 1 | <?xml version="1.0" encoding="UTF-8"?>
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[6732c094] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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[4122007] | 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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[4afc2603] | 8 | <sect1 id="pkgmgt">
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[1f24363] | 9 | <?dbhtml filename="pkgmgt.html"?>
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| 10 |
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| 11 |
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| 12 | <title>Package Management</title>
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| 13 |
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| 14 | <para>Package Management is an often requested addition
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| 15 | to the LFS Book. A Package Manager allows tracking
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| 16 | the installation of files making it easy to remove and upgrade packages.
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| 17 | And before you begin to wonder, NO—this section does not talk about any
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| 18 | particular package manager, nor does it recommend one. What it provides is
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| 19 | a roundup of the more popular techniques and how they work. The perfect
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| 20 | package manager for you may be among these techniques or may be a combination
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| 21 | of two or more of these techniques. This section briefly mentions
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| 22 | issues that may arise when upgrading packages.</para>
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| 23 |
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| 24 | <para>Some reasons why no package manager is mentioned in LFS
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| 25 | or BLFS:</para>
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| 26 |
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| 27 | <itemizedlist>
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| 28 | <listitem>
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| 29 | <para>Dealing with package management takes the focus away from
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| 30 | the goals of these books—teaching how a Linux system is built.</para>
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| 31 | </listitem>
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| 32 | <listitem>
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| 33 | <para>There are multiple solutions for package management, each having
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[919683dc] | 34 | its strengths and drawbacks. Including one that satisfies all audiences is
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[1f24363] | 35 | difficult.</para>
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| 36 | </listitem>
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| 37 | </itemizedlist>
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| 38 |
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| 39 | <para>There are some hints written on the topic of package management. Visit
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[01bf7b38] | 40 | the <ulink url="&hints-root;">Hints subproject</ulink>
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[4afc2603] | 41 | and see if one of them fits your need.</para>
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[1f24363] | 42 |
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| 43 | <sect2>
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| 44 | <title>Upgrade Issues</title>
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| 45 |
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[24ca7aa] | 46 | <para>A Package Manager makes it easy to upgrade to newer versions when
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| 47 | they are released. Generally the instructions in the LFS and BLFS Book can be
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| 48 | used to upgrade to the newer versions. Here are some points that you should
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[1f24363] | 49 | be aware of when upgrading packages, especially on a running system.</para>
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| 50 |
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| 51 | <itemizedlist>
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| 52 | <listitem>
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[4382a36] | 53 | <para>If one of the toolchain packages
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| 54 | (<application>Glibc</application>, <application>GCC</application> or
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| 55 | <application>Binutils</application>) needs to be upgraded to a newer
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[919683dc] | 56 | minor version, it is safer to rebuild LFS. Though you
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[4382a36] | 57 | <emphasis>may</emphasis> be able to get by rebuilding all the packages
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| 58 | in their dependency order, we do not recommend it. For example, if
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| 59 | glibc-2.2.x needs to be updated to glibc-2.3.x, it is safer to rebuild.
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| 60 | For micro version updates, a simple reinstallation usually works, but
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| 61 | is not guaranteed. For example, upgrading from glibc-2.3.4 to
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| 62 | glibc-2.3.5 will not usually cause any problems.</para>
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[1f24363] | 63 | </listitem>
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| 64 | <listitem>
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| 65 | <para>If a package containing a shared library is updated, and if the
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[4382a36] | 66 | name of the library changes, then all the packages dynamically linked
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| 67 | to the library need to be recompiled to link against the newer library.
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| 68 | (Note that there is no correlation between the package version and the
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| 69 | name of the library.) For example, consider a package foo-1.2.3 that
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| 70 | installs a shared library with name
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| 71 | <filename class='libraryfile'>libfoo.so.1</filename>. Say you upgrade
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| 72 | the package to a newer version foo-1.2.4 that installs a shared library
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| 73 | with name <filename class='libraryfile'>libfoo.so.2</filename>. In this
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| 74 | case, all packages that are dynamically linked to
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| 75 | <filename class='libraryfile'>libfoo.so.1</filename> need to be
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| 76 | recompiled to link against
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| 77 | <filename class='libraryfile'>libfoo.so.2</filename>. Note that you
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| 78 | should not remove the previous libraries until the dependent packages
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| 79 | are recompiled.</para>
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[1f24363] | 80 | </listitem>
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| 81 | <listitem>
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[24ca7aa] | 82 | <para>If you are upgrading a running system, be on the lookout for packages
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[1f24363] | 83 | that use <command>cp</command> instead of <command>install</command>
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[4afc2603] | 84 | to install files. The latter command is usually safer if the executable
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| 85 | or library is already loaded in memory.</para>
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[1f24363] | 86 | </listitem>
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| 87 | </itemizedlist>
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| 88 |
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| 89 | </sect2>
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| 90 |
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| 91 | <sect2>
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| 92 | <title>Package Management Techniques</title>
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| 93 |
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| 94 | <para>The following are some common package management techniques. Before
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[4382a36] | 95 | making a decision on a package manager, do some research on the various
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[1f24363] | 96 | techniques, particularly the drawbacks of the particular scheme.</para>
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| 97 |
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| 98 | <sect3>
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| 99 | <title>It is All in My Head!</title>
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| 100 |
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| 101 | <para>Yes, this is a package management technique. Some folks do not find the
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| 102 | need for a package manager because they know the packages intimately and know
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| 103 | what files are installed by each package. Some users also do not need any
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| 104 | package management because they plan on rebuilding the entire system
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| 105 | when a package is changed.</para>
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| 106 |
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| 107 | </sect3>
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| 108 |
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| 109 | <sect3>
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| 110 | <title>Install in Separate Directories</title>
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| 111 |
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[4afc2603] | 112 | <para>This is a simplistic package management that does not need any
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| 113 | extra package to manage the installations. Each package is installed in a
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| 114 | separate directory. For example, package foo-1.1 is installed in
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[4382a36] | 115 | <filename class='directory'>/usr/pkg/foo-1.1</filename>
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[1f24363] | 116 | and a symlink is made from <filename>/usr/pkg/foo</filename> to
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[4382a36] | 117 | <filename class='directory'>/usr/pkg/foo-1.1</filename>. When installing
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| 118 | a new version foo-1.2, it is installed in
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| 119 | <filename class='directory'>/usr/pkg/foo-1.2</filename> and the previous
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| 120 | symlink is replaced by a symlink to the new version.</para>
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[1f24363] | 121 |
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[4382a36] | 122 | <para>The environment variables such as those mentioned in
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[4afc2603] | 123 | <quote><xref linkend="beyond"/></quote> need to be expanded to
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[1f24363] | 124 | include <filename>/usr/pkg/foo</filename>. For more than a few packages,
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| 125 | this scheme becomes unmanageable.</para>
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| 126 |
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| 127 | </sect3>
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| 128 |
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| 129 | <sect3>
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| 130 | <title>Symlink Style Package Management</title>
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| 131 |
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[4382a36] | 132 | <para>This is a variation of the previous package management technique.
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| 133 | Each package is installed similar to the previous scheme. But instead of
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| 134 | making the symlink, each file is symlinked into the
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| 135 | <filename class='directory'>/usr</filename> hierarchy. This removes the
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| 136 | need to expand the environment variables. Though the symlinks can be
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| 137 | created by the user to automate the creation, many package managers have
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| 138 | been written using this approach. A few of the popular ones are Stow,
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| 139 | Epkg, Graft, and Depot.</para>
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[1f24363] | 140 |
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| 141 | <para>The installation needs to be faked, so that the package thinks that it is
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[24ca7aa] | 142 | installed in <filename class="directory">/usr</filename> though in reality it is
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[4382a36] | 143 | installed in the <filename class="directory">/usr/pkg</filename> hierarchy.
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[24ca7aa] | 144 | Installing in this manner is not usually a trivial task. For example, consider
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| 145 | that you are installing a package libfoo-1.1. The following instructions may
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[1f24363] | 146 | not install the package properly:</para>
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| 147 |
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[24ca7aa] | 148 | <screen><userinput>./configure --prefix=/usr/pkg/libfoo/1.1
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[20828163] | 149 | make
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[1f24363] | 150 | make install</userinput></screen>
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[3d760b6] | 151 |
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[4382a36] | 152 | <para>The installation will work, but the dependent packages may not link
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| 153 | to libfoo as you would expect. If you compile a package that links against
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| 154 | libfoo, you may notice that it is linked to
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| 155 | <filename class='libraryfile'>/usr/pkg/libfoo/1.1/lib/libfoo.so.1</filename>
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| 156 | instead of <filename class='libraryfile'>/usr/lib/libfoo.so.1</filename>
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| 157 | as you would expect. The correct approach is to use <envar>DESTDIR</envar>
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| 158 | strategy to fake installation of the package. This approach works as
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| 159 | follows:</para>
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[3d760b6] | 160 |
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[1f24363] | 161 | <screen><userinput>./configure --prefix=/usr
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[20828163] | 162 | make
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[1f24363] | 163 | make DESTDIR=/usr/pkg/libfoo/1.1 install</userinput></screen>
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[3d760b6] | 164 |
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[4382a36] | 165 | <para>Most of the packages do support this approach, but there are some
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| 166 | which do not. For the non-compliant packages, you may either need to
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| 167 | manually install the package, or you may find that it is easier to install
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| 168 | some problematic packages into
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| 169 | <filename class='directory'>/opt</filename>.</para>
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[3d760b6] | 170 |
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[1f24363] | 171 | </sect3>
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[3d760b6] | 172 |
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[1f24363] | 173 | <sect3>
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| 174 | <title>Timestamp Based</title>
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[3d760b6] | 175 |
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[4382a36] | 176 | <para>In this technique, a file is timestamped before the installation of
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| 177 | the package. After the installation, a simple use of the
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| 178 | <command>find</command> command with the appropriate options can generate
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| 179 | a log of all the files installed after the timestamp file was created. A
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| 180 | package manager written with this approach is install-log.</para>
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[3d760b6] | 181 |
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[1f24363] | 182 | <para>Though this scheme has the advantage of being simple, it has two drawbacks.
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| 183 | If during installation, the files are installed with any timestamp other than the
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| 184 | current time, those files will not be tracked by the package manager. Also, this
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| 185 | scheme can only be used when one package is installed at a time. The logs are not
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| 186 | reliable if two packages are being installed on two different consoles.</para>
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[3d760b6] | 187 |
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[1f24363] | 188 | </sect3>
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[3d760b6] | 189 |
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[1f24363] | 190 | <sect3>
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| 191 | <title>LD_PRELOAD Based</title>
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[3d760b6] | 192 |
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[1f24363] | 193 | <para>In this approach, a library is preloaded before installation. During
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| 194 | installation, this library tracks the packages that are being installed by
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| 195 | attaching itself to various executables such as <command>cp</command>,
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| 196 | <command>install</command>, <command>mv</command> and tracking the system
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| 197 | calls that modify the filesystem. For this approach to work, all the executables
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[919683dc] | 198 | need to be dynamically linked without the suid or sgid bit. Preloading the
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[1f24363] | 199 | library may cause some unwanted side-effects during installation. Therefore,
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| 200 | do perform some tests to ensure that the package manager does not break
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| 201 | anything and logs all the appropriate files.</para>
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[3d760b6] | 202 |
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[1f24363] | 203 | </sect3>
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[3d760b6] | 204 |
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[1f24363] | 205 | <sect3>
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| 206 | <title>Creating Package Archives</title>
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[3d760b6] | 207 |
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[1f24363] | 208 | <para>In this scheme, the package installation is faked into a separate
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| 209 | tree as described in the Symlink style package management. After the
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| 210 | installation, a package archive is created using the installed files.
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| 211 | This archive is then used to install the package either on the local
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| 212 | machine or can even be used to install the package on other machines.</para>
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[3d760b6] | 213 |
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[1f24363] | 214 | <para>This approach is used by most of the package managers found in the
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| 215 | commercial distributions. Examples of package managers that follow this
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| 216 | approach are RPM, pkg-utils, Debian's apt, and Gentoo's Portage system.</para>
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[3d760b6] | 217 |
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[1f24363] | 218 | </sect3>
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[3d760b6] | 219 |
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[1f24363] | 220 | <sect3>
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| 221 | <title>User Based Management</title>
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[3d760b6] | 222 |
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[4382a36] | 223 | <para>This scheme, unique to LFS, was devised by Matthias Benkmann,
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[01bf7b38] | 224 | and is available from the <ulink url="&hints-root;">Hints
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[24ca7aa] | 225 | Project</ulink>. In this scheme, each package is installed as a separate user
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| 226 | into the standard locations. Files belonging to a package are easily identified
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[4382a36] | 227 | by checking the user ID. The features and shortcomings of this approach are
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[1f24363] | 228 | too complex to describe in this section. For the details please see the hint at <ulink
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[01bf7b38] | 229 | url="&hints-root;/downloads/files/more_control_and_pkg_man.txt"/>.</para>
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[3d760b6] | 230 |
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[1f24363] | 231 | </sect3>
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[3d760b6] | 232 |
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[1f24363] | 233 | </sect2>
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[3d760b6] | 234 |
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| 235 | </sect1>
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