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| 4 | <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.1 2003/11/20 10:52:35 swift Exp $ --> |
4 | <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.2 2003/11/25 17:34:47 swift Exp $ --> |
| 5 | |
5 | |
| 6 | <sections> |
6 | <sections> |
| 7 | <section> |
7 | <section> |
| 8 | <title>What are USE-flags?</title> |
8 | <title>What are USE-flags?</title> |
| 9 | <subsection> |
9 | <subsection> |
| 10 | <title>The ideas behind USE-flags</title> |
10 | <title>The ideas behind USE-flags</title> |
| 11 | <body> |
11 | <body> |
| 12 | |
12 | |
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13 | <p> |
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14 | When you are installing Gentoo (or any other distribution, or even operating |
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15 | system for that matter) you make choices depending on the environment you are |
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16 | working with. A setup for a server differs from a setup for a workstation. |
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17 | A gaming workstation differs from a 3D rendering workstation. |
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18 | </p> |
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19 | |
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20 | <p> |
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21 | This is not only true for choosing what packages you want to install, but also |
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22 | what features a certain package should support. If you don't need OpenGL, why |
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23 | would you bother installing OpenGL and build OpenGL support in most of your |
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24 | packages? If you don't want to use KDE, why would you bother compiling packages |
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25 | with KDE-support if those packages work flawless without? |
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26 | </p> |
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27 | |
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28 | <p> |
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29 | To help users in deciding what to install/activate and what not, we wanted the |
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30 | user to specify his environment in an easy way. This forces the user into |
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31 | deciding what he really wants and eases the process for Portage, our package |
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32 | managment system, to make usefull decisions. |
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33 | </p> |
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34 | |
| 13 | </body> |
35 | </body> |
| 14 | </subsection> |
36 | </subsection> |
| 15 | <subsection> |
37 | <subsection> |
| 16 | <title>Definition of a USE-flag</title> |
38 | <title>Definition of a USE-flag</title> |
| 17 | <body> |
39 | <body> |
| 18 | |
40 | |
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41 | <p> |
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42 | Enter the USE-flags. Such a flag is a keyword that embodies support and |
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43 | dependency-information for a certain concept. If you define a certain USE-flag, |
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44 | Portage will know that you want support for the chosen keyword. Ofcourse |
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45 | this also alters the dependency information for a package. |
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46 | </p> |
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47 | |
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48 | <p> |
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49 | Lets take a look at a specific example: the <c>kde</c> keyword. If you do not |
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50 | have this keyword in your <c>USE</c> variable, all packages that have |
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51 | <e>optional</e> KDE support will be compiled <e>without</e> KDE support. All |
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52 | packages that have an <e>optional</e> KDE dependency will be installed |
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53 | <e>without</e> installing the KDE libraries (as dependency). If you have defined |
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54 | the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE |
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55 | support, and the KDE libraries will be installed as dependency. |
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56 | </p> |
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57 | |
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58 | <p> |
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59 | By correctly defining the keywords you will receive a system tailored |
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60 | specifically to your needs. |
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61 | </p> |
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62 | |
| 19 | </body> |
63 | </body> |
| 20 | </subsection> |
64 | </subsection> |
| 21 | <subsection> |
65 | <subsection> |
| 22 | <title>What USE-flags exist?</title> |
66 | <title>What USE-flags exist?</title> |
| 23 | <body> |
67 | <body> |
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68 | |
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69 | <p> |
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70 | There are two types of USE-flags: <e>global</e> and <e>local</e> USE-flags. |
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71 | </p> |
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72 | |
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73 | <ul> |
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74 | <li> |
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75 | A <e>global</e> USE-flag is used by several packages, system-wide. This is |
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76 | what most people see as USE-flags. |
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77 | </li> |
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78 | <li> |
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79 | A <e>local</e> USE-fag is used by a single package to make package-specific |
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80 | decisions. |
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81 | </li> |
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82 | </ul> |
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83 | |
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84 | <p> |
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85 | A list of available global USE-flags can be found <uri |
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86 | link="/dyn/use-index.xml">online</uri> or locally in |
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87 | <path>/usr/portage/profiles/use.desc</path>. A short (<e>very</e> incomplete) |
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88 | snippet: |
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89 | </p> |
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90 | |
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91 | <pre caption="A short snippet of available USE-flags"> |
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92 | gtk - Adds support for x11-libs/gtk+ (The GIMP Toolkit) |
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93 | gtk2 - Use gtk+-2.0.0 over gtk+-1.2 in cases where a program supports both. |
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94 | gtkhtml - Adds support for gnome-extra/gtkhtml |
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95 | guile - Adds support for dev-util/guile (interpreter for Scheme) |
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96 | icc - Use the Intel C++ Compiler if the package supports it |
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97 | icc-pgo - Enable PGO data generation or use when use icc. |
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98 | imap - Adds support for IMAP |
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99 | </pre> |
| 24 | |
100 | |
| 25 | </body> |
101 | </body> |
| 26 | </subsection> |
102 | </subsection> |
| 27 | </section> |
103 | </section> |
| 28 | <section> |
104 | <section> |
| 29 | <title>Using USE-flags</title> |
105 | <title>Using USE-flags</title> |
| 30 | <subsection> |
106 | <subsection> |
| 31 | <title>Declare permanent USE-flags</title> |
107 | <title>Declare permanent USE-flags</title> |
| 32 | <body> |
108 | <body> |
| 33 | |
109 | |
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110 | <p> |
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111 | In the hope you are convinced of the importance of USE-flags we will now inform |
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112 | you how to declare USE-flags. |
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113 | </p> |
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114 | |
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115 | <p> |
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116 | As previously mentioned, all USE-flags are declared inside the <c>USE</c> |
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117 | variable. To make it easy for users to search and pick USE-flags, we already |
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118 | provide a <e>default</e> USE setting. This setting is a collection of USE-flags |
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119 | we think are commonly used by the Gentoo users. This default setting is declared |
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120 | in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at |
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121 | this default setting: |
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122 | </p> |
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123 | |
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124 | <pre caption="/etc/make.profile/make.defaults USE variable"> |
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125 | USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm gtk |
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126 | imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses nls |
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127 | oggvorbis opengl pam pdflib png python qt quicktime readline sdl slang |
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128 | spell ssl svga tcpd truetype X xml2 xmms xv zlib" |
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129 | </pre> |
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130 | |
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131 | <p> |
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132 | As you can see, this variable already contains quite a lot of keywords. Do |
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133 | <b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor |
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134 | the <c>USE</c> variable to your needs: changes in this file will be undone when |
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135 | you update Portage! |
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136 | </p> |
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137 | |
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138 | <p> |
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139 | To change this default setting, you need to add or remove keywords to the |
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140 | <c>USE</c> variable. This is done globally by defining the <c>USE</c> variable |
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141 | in <path>/etc/make.conf</path>. In this variable you add the extra USE-flags you |
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142 | require, or remove the USE-flags you don't want. This latter is done by |
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143 | prefixing the keyword with the minus-sign ("-"). |
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144 | </p> |
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145 | |
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146 | <p> |
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147 | For instance, to remove support for KDE and QT but add support for ldap, the |
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148 | following <c>USE</c> can be defined in <path>/etc/make.conf</path>: |
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149 | </p> |
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150 | |
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151 | <pre caption="An example USE setting in /etc/make.conf"> |
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152 | USE="-kde -qt ldap" |
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153 | </pre> |
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154 | |
| 34 | </body> |
155 | </body> |
| 35 | </subsection> |
156 | </subsection> |
| 36 | <subsection> |
157 | <subsection> |
| 37 | <title>Declare temporary USE-flags</title> |
158 | <title>Declare temporary USE-flags</title> |
| 38 | <body> |
159 | <body> |
| 39 | |
160 | |
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161 | <p> |
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162 | Sometimes you want to set a certain USE-setting only once. Instead of editing |
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163 | <path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just |
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164 | declare the USE-variable as environment variable. |
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165 | </p> |
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166 | |
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167 | <p> |
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168 | As an example we will temporarily remove java from the USE-setting |
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169 | during the installation of mozilla. |
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170 | </p> |
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171 | |
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172 | <note> |
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173 | The <c>emerge</c> command will be discussed more thoroughly in <uri |
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174 | link="?part=2&chap=2">Portage and Software</uri>. |
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175 | </note> |
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176 | |
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177 | <pre caption="Using USE as evironment variable"> |
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178 | # <i>USE="-java" emerge mozilla</i> |
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179 | </pre> |
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180 | |
| 40 | </body> |
181 | </body> |
| 41 | </subsection> |
182 | </subsection> |
| 42 | <subsection> |
183 | <subsection> |
| 43 | <title>Inheriting USE-flags</title> |
184 | <title>Inheriting USE-flags</title> |
| 44 | <body> |
185 | <body> |
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186 | |
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187 | <p> |
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188 | Some packages don't only listen to USE-flags, but also provide USE-flags. When |
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189 | you install such a package, the USE-flag they provide is added to your USE |
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190 | setting. To view the list of packages that provide a USE-flag, check |
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191 | <path>/etc/make.profile/use.defaults</path>: |
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192 | </p> |
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193 | |
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194 | <pre caption="A snippet from /etc/make.profile/use.defaults"> |
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195 | gnome gnome-base/gnome |
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196 | gtk x11-libs/gtk+ |
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197 | qt x11-libs/qt |
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198 | kde kde-base/kdebase |
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199 | motif x11-libs/openmotif |
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200 | </pre> |
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201 | |
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202 | </body> |
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203 | </subsection> |
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204 | <subsection> |
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205 | <title>Precendence</title> |
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206 | <body> |
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207 | |
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208 | <p> |
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209 | Ofcourse there is a certain precendence on what setting has priority over the |
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210 | USE setting. You don't want to declare <c>USE="-java"</c> only to see that |
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211 | <c>java</c> is declared anyway. The precedence for the USE setting is, ordered |
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212 | by priority (first has lowest priority): |
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213 | </p> |
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214 | |
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215 | <ol> |
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216 | <li> |
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217 | Default USE setting declared in <path>/etc/make.profile/make.defaults</path> |
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218 | </li> |
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219 | <li> |
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220 | Inherited USE setting if a package from |
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221 | <path>/etc/make.profile/use.defaults</path> is installed |
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222 | </li> |
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223 | <li> |
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224 | User-defined USE setting in <path>/etc/make.conf</path> |
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225 | </li> |
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226 | <li> |
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227 | User-defined USE setting as environment variable |
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228 | </li> |
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229 | </ol> |
| 45 | |
230 | |
| 46 | </body> |
231 | </body> |
| 47 | </subsection> |
232 | </subsection> |
| 48 | </section> |
233 | </section> |
| 49 | <section> |
234 | <section> |
| 50 | <title>Package specific USE-flags</title> |
235 | <title>Package specific USE-flags</title> |
| 51 | <subsection> |
236 | <subsection> |
| 52 | <title>Viewing used USE-flags</title> |
237 | <title>Viewing available USE-flags</title> |
| 53 | <body> |
238 | <body> |
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239 | |
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240 | <p> |
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241 | In the next chapter on <uri link="?part=2&chap=2">Portage and Software</uri> |
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242 | we will explain how to manage your installed software and how to work with |
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243 | <c>emerge</c>. However, we will give you a primer on <c>emerge</c> by showing |
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244 | you how to view what USE-flags a package uses. |
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245 | </p> |
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246 | |
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247 | <p> |
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248 | Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To |
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249 | find out, we use <c>emerge</c> with the <c>--pretend</c> (don't really do |
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250 | anything) and <c>--verbose</c> (give more output) options: |
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251 | </p> |
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252 | |
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253 | <pre caption="Viewing the used USE-flags"> |
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254 | # <i>emerge --pretend --verbose mozilla</i> |
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255 | These are the packages that I would merge, in order: |
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256 | |
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257 | Calculating dependencies ...done! |
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258 | [ebuild N ] net-www/mozilla-1.5-r1 +java +crypt -ipv6 -gtk2 +ssl +ldap |
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259 | +gnome -debug +mozcalendar -mozaccess -mozxmlterm -moznoirc -moznomail |
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260 | -moznocompose -moznoxft |
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261 | </pre> |
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262 | |
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263 | <p> |
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264 | <c>emerge</c> isn't the only tool for this job. In fact, we have a tool |
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265 | dedicated to package information called <c>etcat</c> which resides in the |
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266 | <c>gentoolkit</c> package. First, install <c>gentoolkit</c>: |
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267 | </p> |
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268 | |
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269 | <pre caption="Installing gentoolkit"> |
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270 | # <i>emerge --usepkg gentoolkit</i> |
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271 | </pre> |
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272 | |
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273 | <p> |
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274 | Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a |
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275 | certain package. For instance, for the <c>gnumeric</c> package: |
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276 | </p> |
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277 | |
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278 | <pre caption="Using etcat to view used USE-flags"> |
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279 | # <i>etcat uses gnumeric</i> |
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280 | [ Colour Code : <i>set</i> <comment>unset</comment> ] |
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281 | [ Legend : (U) Col 1 - Current USE flags ] |
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282 | [ : (I) Col 2 - Installed With USE flags ] |
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283 | |
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284 | U I [ Found these USE variables in : app-office/gnumeric-1.2.0 ] |
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285 | - - <comment>libgda</comment> : Adds GNU Data Access (CORBA wrapper) support for gnumeric |
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286 | - - <comment>gnomedb</comment> : unknown |
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287 | + + <i>python</i> : Adds support/bindings for the Python language |
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288 | + + <i>bonobo</i> : Adds support for gnome-base/bonobo (Gnome CORBA interfaces) |
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289 | </pre> |
| 54 | |
290 | |
| 55 | </body> |
291 | </body> |
| 56 | </subsection> |
292 | </subsection> |
| 57 | </section> |
293 | </section> |
| 58 | </sections> |
294 | </sections> |
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