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1<?xml version='1.0' encoding='UTF-8'?>
2<!DOCTYPE sections SYSTEM "/dtd/book.dtd">
3
1<!-- The content of this document is licensed under the CC-BY-SA license --> 4<!-- The content of this document is licensed under the CC-BY-SA license -->
2<!-- See http://creativecommons.org/licenses/by-sa/1.0 --> 5<!-- See http://creativecommons.org/licenses/by-sa/1.0 -->
3 6
4<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.5 2003/12/16 18:08:56 swift Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.14 2004/06/30 21:44:46 neysx Exp $ -->
5 8
6<sections> 9<sections>
7<section> 10<section>
8<title>What are USE-flags?</title> 11<title>What are USE-flags?</title>
9<subsection> 12<subsection>
25with KDE-support if those packages work flawlessly without? 28with KDE-support if those packages work flawlessly without?
26</p> 29</p>
27 30
28<p> 31<p>
29To help users in deciding what to install/activate and what not, we wanted the 32To help users in deciding what to install/activate and what not, we wanted the
30user to specify his environment in an easy way. This forces the user into 33user to specify his/her environment in an easy way. This forces the user into
31deciding what he really wants and eases the process for Portage, our package 34deciding what they really want and eases the process for Portage, our package
32managment system, to make useful decisions. 35managment system, to make useful decisions.
33</p> 36</p>
34 37
35</body> 38</body>
36</subsection> 39</subsection>
44Portage will know that you want support for the chosen keyword. Of course 47Portage will know that you want support for the chosen keyword. Of course
45this also alters the dependency information for a package. 48this also alters the dependency information for a package.
46</p> 49</p>
47 50
48<p> 51<p>
49Lets take a look at a specific example: the <c>kde</c> keyword. If you do not 52Let us take a look at a specific example: the <c>kde</c> keyword. If you do not
50have this keyword in your <c>USE</c> variable, all packages that have 53have this keyword in your <c>USE</c> variable, all packages that have
51<e>optional</e> KDE support will be compiled <e>without</e> KDE support. All 54<e>optional</e> KDE support will be compiled <e>without</e> KDE support. All
52packages that have an <e>optional</e> KDE dependency will be installed 55packages that have an <e>optional</e> KDE dependency will be installed
53<e>without</e> installing the KDE libraries (as dependency). If you have defined 56<e>without</e> installing the KDE libraries (as dependency). If you have defined
54the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE 57the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
74 <li> 77 <li>
75 A <e>global</e> USE-flag is used by several packages, system-wide. This is 78 A <e>global</e> USE-flag is used by several packages, system-wide. This is
76 what most people see as USE-flags. 79 what most people see as USE-flags.
77 </li> 80 </li>
78 <li> 81 <li>
79 A <e>local</e> USE-fag is used by a single package to make package-specific 82 A <e>local</e> USE-flag is used by a single package to make package-specific
80 decisions. 83 decisions.
81 </li> 84 </li>
82</ul> 85</ul>
83 86
84<p> 87<p>
119we think are commonly used by the Gentoo users. This default setting is declared 122we think are commonly used by the Gentoo users. This default setting is declared
120in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at 123in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at
121this default setting: 124this default setting:
122</p> 125</p>
123 126
124<pre caption="/etc/make.profile/make.defaults USE variable"> 127<pre caption="/etc/make.profile/make.defaults USE variable on an x86 system">
125USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm gtk 128USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm
126 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses nls 129 gtk gtk2 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses
127 oggvorbis opengl pam pdflib png python qt quicktime readline sdl slang 130 nls oggvorbis opengl pam pdflib png python qt quicktime readline sdl
128 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 131 slang spell ssl svga tcpd truetype X xml2 xmms xv zlib"
129</pre> 132</pre>
130 133
131<p> 134<p>
132As you can see, this variable already contains quite a lot of keywords. Do 135As you can see, this variable already contains quite a lot of keywords. Do
133<b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor 136<b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor
172<note> 175<note>
173The <c>emerge</c> command will be discussed more thoroughly in <uri 176The <c>emerge</c> command will be discussed more thoroughly in <uri
174link="?part=2&amp;chap=2">Portage and Software</uri>. 177link="?part=2&amp;chap=2">Portage and Software</uri>.
175</note> 178</note>
176 179
177<pre caption="Using USE as evironment variable"> 180<pre caption="Using USE as environment variable">
178# <i>USE="-java" emerge mozilla</i> 181# <i>USE="-java" emerge mozilla</i>
179</pre> 182</pre>
180 183
181</body> 184</body>
182</subsection> 185</subsection>
238# <i>emerge info</i> 241# <i>emerge info</i>
239</pre> 242</pre>
240 243
241</body> 244</body>
242</subsection> 245</subsection>
246<subsection>
247<title>Adapting your Entire System to New USE Flags</title>
248<body>
249
250<p>
251If you have altered your USE flags and you wish to update your entire system to
252use the new USE flags, you can try following the next steps to accomplish this.
253Note however that these steps will take a long time to finish and that work is
254on the way to adjust Portage to handle this behaviour quicker and automatically.
255</p>
256
257<p>
258First of all, rebuild your entire system using the new USE flags:
259</p>
260
261<pre caption="Rebuilding your entire system">
262# <i>emerge --emptytree world</i>
263</pre>
264
265<p>
266Next, run Portage' depclean to remove the conditional dependencies that
267were emerged on your "old" system but that have been obsoleted by the new USE
268flags.
269</p>
270
271<warn>
272Running <c>emerge depclean</c> is a dangerous operation and should be handled
273with care. Double-check the provided list of "obsoleted" packages to make sure
274it doesn't remove packages you need. In the following example we add the
275<c>-p</c> switch to have depclean only list the packages without removing them.
276</warn>
277
278<pre caption="Removing obsoleted packages">
279# <i>emerge -p depclean</i>
280</pre>
281
282<p>
283When depclean has finished, your system is using the new USE flag settings.
284</p>
285
286</body>
287</subsection>
243</section> 288</section>
244<section> 289<section>
245<title>Package specific USE-flags</title> 290<title>Package specific USE-flags</title>
246<subsection> 291<subsection>
247<title>Viewing available USE-flags</title> 292<title>Viewing available USE-flags</title>

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