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7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.7 2004/01/08 14:23:17 swift Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.36 2005/10/26 14:37:18 rane Exp $ -->
8 8
9<sections> 9<sections>
10
11<version>1.31</version>
12<date>2005-10-26</date>
13
10<section> 14<section>
11<title>What are USE-flags?</title> 15<title>What are USE-flags?</title>
12<subsection> 16<subsection>
13<title>The ideas behind USE-flags</title> 17<title>The ideas behind USE-flags</title>
14<body> 18<body>
28with KDE-support if those packages work flawlessly without? 32with KDE-support if those packages work flawlessly without?
29</p> 33</p>
30 34
31<p> 35<p>
32To 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
33user 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
34deciding 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
35managment system, to make useful decisions. 39managment system, to make useful decisions.
36</p> 40</p>
37 41
38</body> 42</body>
39</subsection> 43</subsection>
77 <li> 81 <li>
78 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
79 what most people see as USE-flags. 83 what most people see as USE-flags.
80 </li> 84 </li>
81 <li> 85 <li>
82 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
83 decisions. 87 decisions.
84 </li> 88 </li>
85</ul> 89</ul>
86 90
87<p> 91<p>
99icc - Use the Intel C++ Compiler if the package supports it 103icc - Use the Intel C++ Compiler if the package supports it
100icc-pgo - Enable PGO data generation or use when use icc. 104icc-pgo - Enable PGO data generation or use when use icc.
101imap - Adds support for IMAP 105imap - Adds support for IMAP
102</pre> 106</pre>
103 107
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
104</body> 113</body>
105</subsection> 114</subsection>
106</section> 115</section>
107<section> 116<section>
108<title>Using USE-flags</title> 117<title>Using USE-flags</title>
118<p> 127<p>
119As previously mentioned, all USE-flags are declared inside the <c>USE</c> 128As previously mentioned, all USE-flags are declared inside the <c>USE</c>
120variable. To make it easy for users to search and pick USE-flags, we already 129variable. To make it easy for users to search and pick USE-flags, we already
121provide a <e>default</e> USE setting. This setting is a collection of USE-flags 130provide a <e>default</e> USE setting. This setting is a collection of USE-flags
122we 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
123in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at 132in the <path>make.defaults</path> files part of your profile.
124this default setting: 133</p>
134
125</p> 135<p>
136The profile your system listens to is pointed to by the
137<path>/etc/make.profile</path> symlink. Each profile works on top of another,
138larger profile, the end result is therefore the sum of all profiles. The top
139profile is the <path>base</path> profile
140(<path>/usr/portage/profiles/base</path>).
141</p>
126 142
127<pre caption="/etc/make.profile/make.defaults USE variable"> 143<p>
128USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm gtk 144Let us take a look at this default setting for the 2004.3 profile:
129 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses nls 145</p>
130 oggvorbis opengl pam pdflib png python qt quicktime readline sdl slang 146
147<pre caption="Cumulative make.defaults USE variable for the 2004.3 profile">
148<comment>(This example is the sum of the settings in base, default-linux,
149 default-linux/x86 and default-linux/x86/2004.3)</comment>
150USE="x86 oss apm arts avi berkdb bitmap-fonts crypt cups encode fortran f77
151 foomaticdb gdbm gif gpm gtk gtk2 imlib jpeg kde gnome libg++ libwww mad
152 mikmod motif mpeg ncurses nls oggvorbis opengl pam pdflib png python qt
131 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 153 quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
132</pre> 154</pre>
133 155
134<p> 156<p>
135As you can see, this variable already contains quite a lot of keywords. Do 157As you can see, this variable already contains quite a lot of keywords. Do
136<b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor 158<b>not</b> alter any <path>make.defaults</path> file to tailor
137the <c>USE</c> variable to your needs: changes in this file will be undone when 159the <c>USE</c> variable to your needs: changes in this file will be undone when
138you update Portage! 160you update Portage!
139</p> 161</p>
140 162
141<p> 163<p>
156</pre> 178</pre>
157 179
158</body> 180</body>
159</subsection> 181</subsection>
160<subsection> 182<subsection>
183<title>Declaring USE flags for individual packages</title>
184<body>
185
186<p>
187Sometimes you want to declare a certain USE flag for one (or a couple) of
188applications but not system-wide. To accomplish this, you will need to create
189the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
190<path>/etc/portage/package.use</path>.
191</p>
192
193<p>
194For instance, if you don't want <c>berkdb</c> support globally but you do want
195it for <c>mysql</c>, you would add:
196</p>
197
198<pre caption="/etc/portage/package.use example">
199dev-db/mysql berkdb
200</pre>
201
202<p>
203You can of course also explicitly <e>disable</e> USE flags for a certain
204application. For instance, if you don't want <c>java</c> support in PHP:
205</p>
206
207<pre caption="/etc/portage/package.use 2nd example">
208dev-php/php -java
209</pre>
210
211</body>
212</subsection>
213<subsection>
161<title>Declare temporary USE-flags</title> 214<title>Declare temporary USE-flags</title>
162<body> 215<body>
163 216
164<p> 217<p>
165Sometimes you want to set a certain USE-setting only once. Instead of editing 218Sometimes you want to set a certain USE-setting only once. Instead of editing
166<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just 219<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just
167declare the USE-variable as environment variable. 220declare the USE-variable as environment variable. Remember that, when you
221re-emerge or update this application (either explicitly or as part of a system
222update) your changes will be lost!
168</p> 223</p>
169 224
170<p> 225<p>
171As an example we will temporarily remove java from the USE-setting 226As an example we will temporarily remove java from the USE-setting
172during the installation of mozilla. 227during the installation of mozilla.
173</p> 228</p>
174 229
175<note>
176The <c>emerge</c> command will be discussed more thoroughly in <uri
177link="?part=2&amp;chap=2">Portage and Software</uri>.
178</note>
179
180<pre caption="Using USE as evironment variable"> 230<pre caption="Using USE as environment variable">
181# <i>USE="-java" emerge mozilla</i> 231# <i>USE="-java" emerge mozilla</i>
182</pre> 232</pre>
183 233
184</body> 234</body>
185</subsection> 235</subsection>
186<subsection> 236<subsection>
187<title>Inheriting USE-flags</title> 237<title>Automatic USE Flags</title>
188<body> 238<body>
189 239
190<p> 240<p>
191Some packages don't only listen to USE-flags, but also provide USE-flags. When 241After certain packages are installed, additional USE flags will automatically
192you install such a package, the USE-flag they provide is added to your USE 242be enabled for you if you do not explicitly disable them. To view the list
193setting. To view the list of packages that provide a USE-flag, check 243of packages that trigger automatic USE-flags, check
194<path>/etc/make.profile/use.defaults</path>: 244<path>/etc/make.profile/use.defaults</path> and the <path>use.defaults</path>
245files of the parent profiles.
195</p> 246</p>
196 247
197<pre caption="A snippet from /etc/make.profile/use.defaults"> 248<pre caption="A snippet from /etc/make.profile/use.defaults">
198gnome gnome-base/gnome 249gnome gnome-base/gnome
199gtk x11-libs/gtk+ 250gtk x11-libs/gtk+
203</pre> 254</pre>
204 255
205</body> 256</body>
206</subsection> 257</subsection>
207<subsection> 258<subsection>
208<title>Precendence</title> 259<title>Precedence</title>
209<body> 260<body>
210 261
211<p> 262<p>
212Of course there is a certain precendence on what setting has priority over the 263Of course there is a certain precedence on what setting has priority over the
213USE setting. You don't want to declare <c>USE="-java"</c> only to see that 264USE setting. You don't want to declare <c>USE="-java"</c> only to see that
214<c>java</c> is declared anyway. The precedence for the USE setting is, ordered 265<c>java</c> is still used due to a setting that has a higher priority.
266The precedence for the USE setting is, ordered
215by priority (first has lowest priority): 267by priority (first has lowest priority):
216</p> 268</p>
217 269
218<ol> 270<ol>
219 <li> 271 <li>
220 Default USE setting declared in <path>/etc/make.profile/make.defaults</path> 272 Default USE setting declared in the <path>make.defaults</path> files part of
221 </li> 273 your profile
222 <li> 274 </li>
223 Inherited USE setting if a package from 275 <li>
224 <path>/etc/make.profile/use.defaults</path> is installed 276 Inherited USE setting if a package from profile <path>use.defaults</path> is installed
225 </li> 277 </li>
226 <li> 278 <li>
227 User-defined USE setting in <path>/etc/make.conf</path> 279 User-defined USE setting in <path>/etc/make.conf</path>
228 </li> 280 </li>
229 <li> 281 <li>
282 User-defined USE setting in <path>/etc/portage/package.use</path>
283 </li>
284 <li>
230 User-defined USE setting as environment variable 285 User-defined USE setting as environment variable
231 </li> 286 </li>
232</ol> 287</ol>
233 288
234<p> 289<p>
235To view the final <c>USE</c> setting as seen by Portage, run <c>emerge info</c>. 290To view the final <c>USE</c> setting as seen by Portage, run <c>emerge
236This will list all relevant variables (including the <c>USE</c> variable) with 291--info</c>. This will list all relevant variables (including the <c>USE</c>
237the content used by Portage. 292variable) with the content used by Portage.
238</p> 293</p>
239 294
240<pre caption="Running emerge info"> 295<pre caption="Running emerge --info">
241# <i>emerge info</i> 296# <i>emerge --info</i>
297</pre>
298
299</body>
300</subsection>
301<subsection>
302<title>Adapting your Entire System to New USE Flags</title>
303<body>
304
305<p>
306If you have altered your USE flags and you wish to update your entire system to
307use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
242</pre> 308</p>
309
310<pre caption="Rebuilding your entire system">
311# <i>emerge --update --deep --newuse world</i>
312</pre>
313
314<p>
315Next, run Portage's depclean to remove the conditional dependencies that
316were emerged on your "old" system but that have been obsoleted by the new USE
317flags.
318</p>
319
320<warn>
321Running <c>emerge --depclean</c> is a dangerous operation and should be handled
322with care. Double-check the provided list of "obsoleted" packages to make sure
323it doesn't remove packages you need. In the following example we add the
324<c>-p</c> switch to have depclean only list the packages without removing them.
325</warn>
326
327<pre caption="Removing obsoleted packages">
328# <i>emerge -p --depclean</i>
329</pre>
330
331<p>
332When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
333applications that are dynamically linked against shared objects provided by
334possibly removed packages. <c>revdep-rebuild</c> is part of the
335<c>gentoolkit</c> package; don't forget to emerge it first.
336</p>
337
338<pre caption="Running revdep-rebuild">
339# <i>revdep-rebuild</i>
340</pre>
341
342<p>
343When all this is accomplished, your system is using the new USE flag settings.
344</p>
243 345
244</body> 346</body>
245</subsection> 347</subsection>
246</section> 348</section>
247<section> 349<section>
249<subsection> 351<subsection>
250<title>Viewing available USE-flags</title> 352<title>Viewing available USE-flags</title>
251<body> 353<body>
252 354
253<p> 355<p>
254In the next chapter on <uri link="?part=2&amp;chap=2">Portage and Software</uri>
255we will explain how to manage your installed software and how to work with
256<c>emerge</c>. However, we will give you a primer on <c>emerge</c> by showing
257you how to view what USE-flags a package uses.
258</p>
259
260<p>
261Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To 356Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To
262find out, we use <c>emerge</c> with the <c>--pretend</c> (don't really do 357find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
263anything) and <c>--verbose</c> (give more output) options: 358options:
264</p> 359</p>
265 360
266<pre caption="Viewing the used USE-flags"> 361<pre caption="Viewing the used USE-flags">
267# <i>emerge --pretend --verbose mozilla</i> 362# <i>emerge --pretend --verbose mozilla</i>
268These are the packages that I would merge, in order: 363These are the packages that I would merge, in order:
273-moznocompose -moznoxft 368-moznocompose -moznoxft
274</pre> 369</pre>
275 370
276<p> 371<p>
277<c>emerge</c> isn't the only tool for this job. In fact, we have a tool 372<c>emerge</c> isn't the only tool for this job. In fact, we have a tool
278dedicated to package information called <c>etcat</c> which resides in the 373dedicated to package information called <c>equery</c> which resides in the
279<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 374<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
280</p> 375</p>
281 376
282<pre caption="Installing gentoolkit"> 377<pre caption="Installing gentoolkit">
283# <i>emerge --usepkg gentoolkit</i> 378# <i>emerge gentoolkit</i>
284</pre> 379</pre>
285 380
286<p> 381<p>
287Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a 382Now run <c>equery</c> with the <c>uses</c> argument to view the USE-flags of a
288certain package. For instance, for the <c>gnumeric</c> package: 383certain package. For instance, for the <c>gnumeric</c> package:
289</p> 384</p>
290 385
291<pre caption="Using etcat to view used USE-flags"> 386<pre caption="Using equery to view used USE-flags">
292# <i>etcat uses gnumeric</i> 387# <i>equery uses gnumeric</i>
293[ Colour Code : <i>set</i> <comment>unset</comment> ] 388[ Colour Code : <i>set</i> <comment>unset</comment> ]
294[ Legend : (U) Col 1 - Current USE flags ] 389[ Legend : (U) Col 1 - Current USE flags ]
295[ : (I) Col 2 - Installed With USE flags ] 390[ : (I) Col 2 - Installed With USE flags ]
296 391
297 U I [ Found these USE variables in : app-office/gnumeric-1.2.0 ] 392 U I [ Found these USE variables in : app-office/gnumeric-1.2.0 ]

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