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2<!DOCTYPE sections SYSTEM "/dtd/book.dtd">
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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 1.22 2004/11/09 13:01:52 swift Exp $ -->
5 8
6<sections> 9<sections>
10
11<version>1.21</version>
12<date>October 21, 2004</date>
13
7<section> 14<section>
8<title>What are USE-flags?</title> 15<title>What are USE-flags?</title>
9<subsection> 16<subsection>
10<title>The ideas behind USE-flags</title> 17<title>The ideas behind USE-flags</title>
11<body> 18<body>
25with KDE-support if those packages work flawlessly without? 32with KDE-support if those packages work flawlessly without?
26</p> 33</p>
27 34
28<p> 35<p>
29To help users in deciding what to install/activate and what not, we wanted the 36To 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 37user 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 38deciding what they really want and eases the process for Portage, our package
32managment system, to make useful decisions. 39managment system, to make useful decisions.
33</p> 40</p>
34 41
35</body> 42</body>
36</subsection> 43</subsection>
44Portage will know that you want support for the chosen keyword. Of course 51Portage will know that you want support for the chosen keyword. Of course
45this also alters the dependency information for a package. 52this also alters the dependency information for a package.
46</p> 53</p>
47 54
48<p> 55<p>
49Lets take a look at a specific example: the <c>kde</c> keyword. If you do not 56Let 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 57have 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 58<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 59packages 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 60<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 61the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
74 <li> 81 <li>
75 A <e>global</e> USE-flag is used by several packages, system-wide. This is 82 A <e>global</e> USE-flag is used by several packages, system-wide. This is
76 what most people see as USE-flags. 83 what most people see as USE-flags.
77 </li> 84 </li>
78 <li> 85 <li>
79 A <e>local</e> USE-fag is used by a single package to make package-specific 86 A <e>local</e> USE-flag is used by a single package to make package-specific
80 decisions. 87 decisions.
81 </li> 88 </li>
82</ul> 89</ul>
83 90
84<p> 91<p>
96icc - Use the Intel C++ Compiler if the package supports it 103icc - Use the Intel C++ Compiler if the package supports it
97icc-pgo - Enable PGO data generation or use when use icc. 104icc-pgo - Enable PGO data generation or use when use icc.
98imap - Adds support for IMAP 105imap - Adds support for IMAP
99</pre> 106</pre>
100 107
108<p>
109A list of available local USE-flags can be found locally in
110<path>/usr/portage/profiles/use.local.desc</path>.
111</p>
112
101</body> 113</body>
102</subsection> 114</subsection>
103</section> 115</section>
104<section> 116<section>
105<title>Using USE-flags</title> 117<title>Using USE-flags</title>
119we think are commonly used by the Gentoo users. This default setting is declared 131we 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 132in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at
121this default setting: 133this default setting:
122</p> 134</p>
123 135
124<pre caption="/etc/make.profile/make.defaults USE variable"> 136<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 137USE="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 138 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 139 nls oggvorbis opengl pam pdflib png python qt quicktime readline sdl
128 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 140 slang spell ssl svga tcpd truetype X xml2 xmms xv zlib"
129</pre> 141</pre>
130 142
131<p> 143<p>
132As you can see, this variable already contains quite a lot of keywords. Do 144As 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 145<b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor
153</pre> 165</pre>
154 166
155</body> 167</body>
156</subsection> 168</subsection>
157<subsection> 169<subsection>
170<title>Declaring USE flags for individual packages</title>
171<body>
172
173<p>
174Sometimes you want to declare a certain USE flag for one (or a couple) of
175applications but not system-wide. To accomplish this, you will need to create
176the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
177<path>/etc/portage/package.use</path>.
178</p>
179
180<p>
181For instance, if you don't want <c>berkdb</c> support globally but you do want
182it for <c>mysql</c>, you would add:
183</p>
184
185<pre caption="/etc/portage/package.use example">
186dev-db/mysql berkdb
187</pre>
188
189<p>
190You can of course also explicitly <e>disable</e> USE flags for a certain
191application. For instance, if you don't want <c>java</c> support in PHP:
192</p>
193
194<pre caption="/etc/portage/package.use 2nd example">
195dev-php/php -java
196</pre>
197
198</body>
199</subsection>
200<subsection>
158<title>Declare temporary USE-flags</title> 201<title>Declare temporary USE-flags</title>
159<body> 202<body>
160 203
161<p> 204<p>
162Sometimes you want to set a certain USE-setting only once. Instead of editing 205Sometimes you want to set a certain USE-setting only once. Instead of editing
163<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just 206<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just
164declare the USE-variable as environment variable. 207declare the USE-variable as environment variable. Remember that, when you
208re-emerge or update this application (either explicitly or as part of a system
209update) your changes will be lost!
165</p> 210</p>
166 211
167<p> 212<p>
168As an example we will temporarily remove java from the USE-setting 213As an example we will temporarily remove java from the USE-setting
169during the installation of mozilla. 214during the installation of mozilla.
170</p> 215</p>
171 216
172<note>
173The <c>emerge</c> command will be discussed more thoroughly in <uri
174link="?part=2&amp;chap=2">Portage and Software</uri>.
175</note>
176
177<pre caption="Using USE as evironment variable"> 217<pre caption="Using USE as environment variable">
178# <i>USE="-java" emerge mozilla</i> 218# <i>USE="-java" emerge mozilla</i>
179</pre> 219</pre>
180 220
181</body> 221</body>
182</subsection> 222</subsection>
200</pre> 240</pre>
201 241
202</body> 242</body>
203</subsection> 243</subsection>
204<subsection> 244<subsection>
205<title>Precendence</title> 245<title>Precedence</title>
206<body> 246<body>
207 247
208<p> 248<p>
209Of course there is a certain precendence on what setting has priority over the 249Of course there is a certain precedence on what setting has priority over the
210USE setting. You don't want to declare <c>USE="-java"</c> only to see that 250USE setting. You don't want to declare <c>USE="-java"</c> only to see that
211<c>java</c> is declared anyway. The precedence for the USE setting is, ordered 251<c>java</c> is declared anyway. The precedence for the USE setting is, ordered
212by priority (first has lowest priority): 252by priority (first has lowest priority):
213</p> 253</p>
214 254
222 </li> 262 </li>
223 <li> 263 <li>
224 User-defined USE setting in <path>/etc/make.conf</path> 264 User-defined USE setting in <path>/etc/make.conf</path>
225 </li> 265 </li>
226 <li> 266 <li>
267 User-defined USE setting in <path>/etc/portage/package.use</path>
268 </li>
269 <li>
227 User-defined USE setting as environment variable 270 User-defined USE setting as environment variable
228 </li> 271 </li>
229</ol> 272</ol>
230 273
231<p> 274<p>
238# <i>emerge info</i> 281# <i>emerge info</i>
239</pre> 282</pre>
240 283
241</body> 284</body>
242</subsection> 285</subsection>
286<subsection>
287<title>Adapting your Entire System to New USE Flags</title>
288<body>
289
290<p>
291If you have altered your USE flags and you wish to update your entire system to
292use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
293</p>
294
295<pre caption="Rebuilding your entire system">
296# <i>emerge --update --deep --newuse world</i>
297</pre>
298
299<p>
300Next, run Portage's depclean to remove the conditional dependencies that
301were emerged on your "old" system but that have been obsoleted by the new USE
302flags.
303</p>
304
305<warn>
306Running <c>emerge depclean</c> is a dangerous operation and should be handled
307with care. Double-check the provided list of "obsoleted" packages to make sure
308it doesn't remove packages you need. In the following example we add the
309<c>-p</c> switch to have depclean only list the packages without removing them.
310</warn>
311
312<pre caption="Removing obsoleted packages">
313# <i>emerge -p depclean</i>
314</pre>
315
316<p>
317When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
318applications that are dynamically linked against shared objects provided by
319possibly removed packages. <c>revdep-rebuild</c> is part of the
320<c>gentoolkit</c> package; don't forget to emerge it first.
321</p>
322
323<pre caption="Running revdep-rebuild">
324# <i>revdep-rebuild</i>
325</pre>
326
327<p>
328When all this is accomplished, your system is using the new USE flag settings.
329</p>
330
331</body>
332</subsection>
243</section> 333</section>
244<section> 334<section>
245<title>Package specific USE-flags</title> 335<title>Package specific USE-flags</title>
246<subsection> 336<subsection>
247<title>Viewing available USE-flags</title> 337<title>Viewing available USE-flags</title>
248<body> 338<body>
249 339
250<p> 340<p>
251In the next chapter on <uri link="?part=2&amp;chap=2">Portage and Software</uri>
252we will explain how to manage your installed software and how to work with
253<c>emerge</c>. However, we will give you a primer on <c>emerge</c> by showing
254you how to view what USE-flags a package uses.
255</p>
256
257<p>
258Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To 341Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To
259find out, we use <c>emerge</c> with the <c>--pretend</c> (don't really do 342find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
260anything) and <c>--verbose</c> (give more output) options: 343options:
261</p> 344</p>
262 345
263<pre caption="Viewing the used USE-flags"> 346<pre caption="Viewing the used USE-flags">
264# <i>emerge --pretend --verbose mozilla</i> 347# <i>emerge --pretend --verbose mozilla</i>
265These are the packages that I would merge, in order: 348These are the packages that I would merge, in order:
275dedicated to package information called <c>etcat</c> which resides in the 358dedicated to package information called <c>etcat</c> which resides in the
276<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 359<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
277</p> 360</p>
278 361
279<pre caption="Installing gentoolkit"> 362<pre caption="Installing gentoolkit">
280# <i>emerge --usepkg gentoolkit</i> 363# <i>emerge gentoolkit</i>
281</pre> 364</pre>
282 365
283<p> 366<p>
284Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a 367Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a
285certain package. For instance, for the <c>gnumeric</c> package: 368certain package. For instance, for the <c>gnumeric</c> package:

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