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7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.21 2004/10/21 10:31:20 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>
123<p> 127<p>
124As 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>
125variable. 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
126provide 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
127we 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
128in 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.
129this default setting: 133</p>
134
130</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>
131 142
132<pre caption="/etc/make.profile/make.defaults USE variable on an x86 system"> 143<p>
133USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm 144Let us take a look at this default setting for the 2004.3 profile:
134 gtk gtk2 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses 145</p>
135 nls oggvorbis opengl pam pdflib png python qt quicktime readline sdl 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
136 slang spell ssl svga tcpd truetype X xml2 xmms xv zlib" 153 quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
137</pre> 154</pre>
138 155
139<p> 156<p>
140As 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
141<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
142the <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
143you update Portage! 160you update Portage!
144</p> 161</p>
145 162
146<p> 163<p>
215</pre> 232</pre>
216 233
217</body> 234</body>
218</subsection> 235</subsection>
219<subsection> 236<subsection>
220<title>Inheriting USE-flags</title> 237<title>Automatic USE Flags</title>
221<body> 238<body>
222 239
223<p> 240<p>
224Some packages don't only listen to USE-flags, but also provide USE-flags. When 241After certain packages are installed, additional USE flags will automatically
225you 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
226setting. To view the list of packages that provide a USE-flag, check 243of packages that trigger automatic USE-flags, check
227<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.
228</p> 246</p>
229 247
230<pre caption="A snippet from /etc/make.profile/use.defaults"> 248<pre caption="A snippet from /etc/make.profile/use.defaults">
231gnome gnome-base/gnome 249gnome gnome-base/gnome
232gtk x11-libs/gtk+ 250gtk x11-libs/gtk+
241<title>Precedence</title> 259<title>Precedence</title>
242<body> 260<body>
243 261
244<p> 262<p>
245Of course there is a certain precedence on what setting has priority over the 263Of course there is a certain precedence on what setting has priority over the
246USE 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
247<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
248by priority (first has lowest priority): 267by priority (first has lowest priority):
249</p> 268</p>
250 269
251<ol> 270<ol>
252 <li> 271 <li>
253 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
254 </li> 273 your profile
255 <li> 274 </li>
256 Inherited USE setting if a package from 275 <li>
257 <path>/etc/make.profile/use.defaults</path> is installed 276 Inherited USE setting if a package from profile <path>use.defaults</path> is installed
258 </li> 277 </li>
259 <li> 278 <li>
260 User-defined USE setting in <path>/etc/make.conf</path> 279 User-defined USE setting in <path>/etc/make.conf</path>
261 </li> 280 </li>
262 <li> 281 <li>
266 User-defined USE setting as environment variable 285 User-defined USE setting as environment variable
267 </li> 286 </li>
268</ol> 287</ol>
269 288
270<p> 289<p>
271To 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
272This 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>
273the content used by Portage. 292variable) with the content used by Portage.
274</p> 293</p>
275 294
276<pre caption="Running emerge info"> 295<pre caption="Running emerge --info">
277# <i>emerge info</i> 296# <i>emerge --info</i>
278</pre> 297</pre>
279 298
280</body> 299</body>
281</subsection> 300</subsection>
282<subsection> 301<subsection>
297were emerged on your "old" system but that have been obsoleted by the new USE 316were emerged on your "old" system but that have been obsoleted by the new USE
298flags. 317flags.
299</p> 318</p>
300 319
301<warn> 320<warn>
302Running <c>emerge depclean</c> is a dangerous operation and should be handled 321Running <c>emerge --depclean</c> is a dangerous operation and should be handled
303with care. Double-check the provided list of "obsoleted" packages to make sure 322with care. Double-check the provided list of "obsoleted" packages to make sure
304it doesn't remove packages you need. In the following example we add the 323it doesn't remove packages you need. In the following example we add the
305<c>-p</c> switch to have depclean only list the packages without removing them. 324<c>-p</c> switch to have depclean only list the packages without removing them.
306</warn> 325</warn>
307 326
308<pre caption="Removing obsoleted packages"> 327<pre caption="Removing obsoleted packages">
309# <i>emerge -p depclean</i> 328# <i>emerge -p --depclean</i>
310</pre> 329</pre>
311 330
312<p> 331<p>
313When depclean has finished, run <c>revdep-rebuild</c> to rebuild the 332When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
314applications that are dynamically linked against shared objects provided by 333applications that are dynamically linked against shared objects provided by
349-moznocompose -moznoxft 368-moznocompose -moznoxft
350</pre> 369</pre>
351 370
352<p> 371<p>
353<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
354dedicated to package information called <c>etcat</c> which resides in the 373dedicated to package information called <c>equery</c> which resides in the
355<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 374<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
356</p> 375</p>
357 376
358<pre caption="Installing gentoolkit"> 377<pre caption="Installing gentoolkit">
359# <i>emerge gentoolkit</i> 378# <i>emerge gentoolkit</i>
360</pre> 379</pre>
361 380
362<p> 381<p>
363Now 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
364certain package. For instance, for the <c>gnumeric</c> package: 383certain package. For instance, for the <c>gnumeric</c> package:
365</p> 384</p>
366 385
367<pre caption="Using etcat to view used USE-flags"> 386<pre caption="Using equery to view used USE-flags">
368# <i>etcat uses gnumeric</i> 387# <i>equery uses gnumeric</i>
369[ Colour Code : <i>set</i> <comment>unset</comment> ] 388[ Colour Code : <i>set</i> <comment>unset</comment> ]
370[ Legend : (U) Col 1 - Current USE flags ] 389[ Legend : (U) Col 1 - Current USE flags ]
371[ : (I) Col 2 - Installed With USE flags ] 390[ : (I) Col 2 - Installed With USE flags ]
372 391
373 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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