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1 | <?xml version='1.0'?> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
6 | SPDX-License-Identifier: LGPL-2.1+ | |
7 | Copyright © 2014 Jason St. John | |
8 | --> | |
9 | ||
10 | <refentry id="udev"> | |
11 | <refentryinfo> | |
12 | <title>udev</title> | |
13 | <productname>systemd</productname> | |
14 | </refentryinfo> | |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>udev</refentrytitle> | |
18 | <manvolnum>7</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>udev</refname> | |
23 | <refpurpose>Dynamic device management</refpurpose> | |
24 | </refnamediv> | |
25 | ||
26 | <refsect1><title>Description</title> | |
27 | <para>udev supplies the system software with device events, manages permissions | |
28 | of device nodes and may create additional symlinks in the <filename>/dev</filename> | |
29 | directory, or renames network interfaces. The kernel usually just assigns unpredictable | |
30 | device names based on the order of discovery. Meaningful symlinks or network device | |
31 | names provide a way to reliably identify devices based on their properties or | |
32 | current configuration.</para> | |
33 | ||
34 | <para>The udev daemon, <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle> | |
35 | <manvolnum>8</manvolnum></citerefentry>, receives device uevents directly from | |
36 | the kernel whenever a device is added or removed from the system, or it changes its | |
37 | state. When udev receives a device event, it matches its configured set of rules | |
38 | against various device attributes to identify the device. Rules that match may | |
39 | provide additional device information to be stored in the udev database or | |
40 | to be used to create meaningful symlink names.</para> | |
41 | ||
42 | <para>All device information udev processes is stored in the udev database and | |
43 | sent out to possible event subscribers. Access to all stored data and the event | |
44 | sources is provided by the library libudev.</para> | |
45 | </refsect1> | |
46 | ||
47 | <refsect1><title>Rules Files</title> | |
48 | <para>The udev rules are read from the files located in the system rules directories | |
49 | <filename>/usr/lib/udev/rules.d</filename> and <filename>/usr/local/lib/udev/rules.d</filename>, the | |
50 | volatile runtime directory <filename>/run/udev/rules.d</filename> and the local administration | |
51 | directory <filename>/etc/udev/rules.d</filename>. All rules files are collectively sorted and | |
52 | processed in lexical order, regardless of the directories in which they live. However, files with | |
53 | identical filenames replace each other. Files in <filename>/etc</filename> have the highest priority, | |
54 | files in <filename>/run</filename> take precedence over files with the same name under | |
55 | <filename>/usr</filename>. This can be used to override a system-supplied rules file with a local | |
56 | file if needed; a symlink in <filename>/etc</filename> with the same name as a rules file in | |
57 | <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>, disables the rules file | |
58 | entirely. Rule files must have the extension <filename>.rules</filename>; other extensions are | |
59 | ignored.</para> | |
60 | ||
61 | <para>Every line in the rules file contains at least one key-value pair. | |
62 | Except for empty lines or lines beginning with <literal>#</literal>, which are ignored. | |
63 | There are two kinds of keys: match and assignment. | |
64 | If all match keys match against their values, the rule gets applied and the | |
65 | assignment keys get the specified values assigned.</para> | |
66 | ||
67 | <para>A matching rule may rename a network interface, add symlinks | |
68 | pointing to the device node, or run a specified program as part of | |
69 | the event handling.</para> | |
70 | ||
71 | <para>A rule consists of a comma-separated list of one or more key-value pairs. | |
72 | Each key has a distinct operation, depending on the used operator. Valid | |
73 | operators are:</para> | |
74 | <variablelist> | |
75 | <varlistentry> | |
76 | <term><literal>==</literal></term> | |
77 | <listitem> | |
78 | <para>Compare for equality.</para> | |
79 | </listitem> | |
80 | </varlistentry> | |
81 | ||
82 | <varlistentry> | |
83 | <term><literal>!=</literal></term> | |
84 | <listitem> | |
85 | <para>Compare for inequality.</para> | |
86 | </listitem> | |
87 | </varlistentry> | |
88 | ||
89 | <varlistentry> | |
90 | <term><literal>=</literal></term> | |
91 | <listitem> | |
92 | <para>Assign a value to a key. Keys that represent a list are reset | |
93 | and only this single value is assigned.</para> | |
94 | </listitem> | |
95 | </varlistentry> | |
96 | ||
97 | <varlistentry> | |
98 | <term><literal>+=</literal></term> | |
99 | <listitem> | |
100 | <para>Add the value to a key that holds a list of entries.</para> | |
101 | </listitem> | |
102 | </varlistentry> | |
103 | ||
104 | <varlistentry> | |
105 | <term><literal>-=</literal></term> | |
106 | <listitem> | |
107 | <para>Remove the value from a key that holds a list of entries.</para> | |
108 | </listitem> | |
109 | </varlistentry> | |
110 | ||
111 | <varlistentry> | |
112 | <term><literal>:=</literal></term> | |
113 | <listitem> | |
114 | <para>Assign a value to a key finally; disallow any later changes.</para> | |
115 | </listitem> | |
116 | </varlistentry> | |
117 | </variablelist> | |
118 | ||
119 | <para>The following key names can be used to match against device properties. | |
120 | Some of the keys also match against properties of the parent devices in sysfs, | |
121 | not only the device that has generated the event. If multiple keys that match | |
122 | a parent device are specified in a single rule, all these keys must match at | |
123 | one and the same parent device.</para> | |
124 | <variablelist class='udev-directives'> | |
125 | <varlistentry> | |
126 | <term><varname>ACTION</varname></term> | |
127 | <listitem> | |
128 | <para>Match the name of the event action.</para> | |
129 | </listitem> | |
130 | </varlistentry> | |
131 | ||
132 | <varlistentry> | |
133 | <term><varname>DEVPATH</varname></term> | |
134 | <listitem> | |
135 | <para>Match the devpath of the event device.</para> | |
136 | </listitem> | |
137 | </varlistentry> | |
138 | ||
139 | <varlistentry> | |
140 | <term><varname>KERNEL</varname></term> | |
141 | <listitem> | |
142 | <para>Match the name of the event device.</para> | |
143 | </listitem> | |
144 | </varlistentry> | |
145 | ||
146 | <varlistentry> | |
147 | <term><varname>NAME</varname></term> | |
148 | <listitem> | |
149 | <para>Match the name of a network interface. It can be used once the | |
150 | NAME key has been set in one of the preceding rules.</para> | |
151 | </listitem> | |
152 | </varlistentry> | |
153 | ||
154 | <varlistentry> | |
155 | <term><varname>SYMLINK</varname></term> | |
156 | <listitem> | |
157 | <para>Match the name of a symlink targeting the node. It can | |
158 | be used once a SYMLINK key has been set in one of the preceding | |
159 | rules. There may be multiple symlinks; only one needs to match. | |
160 | </para> | |
161 | </listitem> | |
162 | </varlistentry> | |
163 | ||
164 | <varlistentry> | |
165 | <term><varname>SUBSYSTEM</varname></term> | |
166 | <listitem> | |
167 | <para>Match the subsystem of the event device.</para> | |
168 | </listitem> | |
169 | </varlistentry> | |
170 | <varlistentry> | |
171 | <term><varname>DRIVER</varname></term> | |
172 | <listitem> | |
173 | <para>Match the driver name of the event device. Only set this key for devices | |
174 | which are bound to a driver at the time the event is generated.</para> | |
175 | </listitem> | |
176 | </varlistentry> | |
177 | <varlistentry> | |
178 | <term><varname>ATTR{<replaceable>filename</replaceable>}</varname></term> | |
179 | <listitem> | |
180 | <para>Match sysfs attribute values of the event device. Trailing | |
181 | whitespace in the attribute values is ignored unless the specified match | |
182 | value itself contains trailing whitespace. | |
183 | </para> | |
184 | </listitem> | |
185 | </varlistentry> | |
186 | <varlistentry> | |
187 | <term><varname>SYSCTL{<replaceable>kernel parameter</replaceable>}</varname></term> | |
188 | <listitem> | |
189 | <para>Match a kernel parameter value. | |
190 | </para> | |
191 | </listitem> | |
192 | </varlistentry> | |
193 | ||
194 | <varlistentry> | |
195 | <term><varname>KERNELS</varname></term> | |
196 | <listitem> | |
197 | <para>Search the devpath upwards for a matching device name.</para> | |
198 | </listitem> | |
199 | </varlistentry> | |
200 | ||
201 | <varlistentry> | |
202 | <term><varname>SUBSYSTEMS</varname></term> | |
203 | <listitem> | |
204 | <para>Search the devpath upwards for a matching device subsystem name.</para> | |
205 | </listitem> | |
206 | </varlistentry> | |
207 | ||
208 | <varlistentry> | |
209 | <term><varname>DRIVERS</varname></term> | |
210 | <listitem> | |
211 | <para>Search the devpath upwards for a matching device driver name.</para> | |
212 | </listitem> | |
213 | </varlistentry> | |
214 | ||
215 | <varlistentry> | |
216 | <term><varname>ATTRS{<replaceable>filename</replaceable>}</varname></term> | |
217 | <listitem> | |
218 | <para>Search the devpath upwards for a device with matching sysfs attribute values. | |
219 | If multiple <varname>ATTRS</varname> matches are specified, all of them | |
220 | must match on the same device. Trailing whitespace in the attribute values is ignored | |
221 | unless the specified match value itself contains trailing whitespace.</para> | |
222 | </listitem> | |
223 | </varlistentry> | |
224 | ||
225 | <varlistentry> | |
226 | <term><varname>TAGS</varname></term> | |
227 | <listitem> | |
228 | <para>Search the devpath upwards for a device with matching tag.</para> | |
229 | </listitem> | |
230 | </varlistentry> | |
231 | ||
232 | <varlistentry> | |
233 | <term><varname>ENV{<replaceable>key</replaceable>}</varname></term> | |
234 | <listitem> | |
235 | <para>Match against a device property value.</para> | |
236 | </listitem> | |
237 | </varlistentry> | |
238 | ||
239 | <varlistentry> | |
240 | <term><varname>CONST{<replaceable>key</replaceable>}</varname></term> | |
241 | <listitem> | |
242 | <para>Match against a system-wide constant. Supported keys are:</para> | |
243 | <variablelist> | |
244 | <varlistentry> | |
245 | <term><literal>arch</literal></term> | |
246 | <listitem> | |
247 | <para>System's architecture. See <option>ConditionArchitecture=</option> in | |
248 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
249 | for possible values.</para> | |
250 | </listitem> | |
251 | </varlistentry> | |
252 | <varlistentry> | |
253 | <term><literal>virt</literal></term> | |
254 | <listitem> | |
255 | <para>System's virtualization environment. See | |
256 | <citerefentry><refentrytitle>systemd-detect-virt</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
257 | for possible values.</para> | |
258 | </listitem> | |
259 | </varlistentry> | |
260 | </variablelist> | |
261 | <para>Unknown keys will never match.</para> | |
262 | </listitem> | |
263 | </varlistentry> | |
264 | ||
265 | <varlistentry> | |
266 | <term><varname>TAG</varname></term> | |
267 | <listitem> | |
268 | <para>Match against a device tag.</para> | |
269 | </listitem> | |
270 | </varlistentry> | |
271 | ||
272 | <varlistentry> | |
273 | <term><varname>TEST{<replaceable>octal mode mask</replaceable>}</varname></term> | |
274 | <listitem> | |
275 | <para>Test the existence of a file. An octal mode mask can be specified | |
276 | if needed.</para> | |
277 | </listitem> | |
278 | </varlistentry> | |
279 | ||
280 | <varlistentry> | |
281 | <term><varname>PROGRAM</varname></term> | |
282 | <listitem> | |
283 | <para>Execute a program to determine whether there | |
284 | is a match; the key is true if the program returns | |
285 | successfully. The device properties are made available to the | |
286 | executed program in the environment. The program's standard output | |
287 | is available in the <varname>RESULT</varname> key.</para> | |
288 | <para>This can only be used for very short-running foreground tasks. For details, | |
289 | see <varname>RUN</varname>.</para> | |
290 | </listitem> | |
291 | </varlistentry> | |
292 | ||
293 | <varlistentry> | |
294 | <term><varname>RESULT</varname></term> | |
295 | <listitem> | |
296 | <para>Match the returned string of the last <varname>PROGRAM</varname> call. | |
297 | This key can be used in the same or in any later rule after a | |
298 | <varname>PROGRAM</varname> call.</para> | |
299 | </listitem> | |
300 | </varlistentry> | |
301 | </variablelist> | |
302 | ||
303 | <para>Most of the fields support shell glob pattern matching and | |
304 | alternate patterns. The following special characters are supported:</para> | |
305 | <variablelist> | |
306 | <varlistentry> | |
307 | <term><literal>*</literal></term> | |
308 | <listitem> | |
309 | <para>Matches zero or more characters.</para> | |
310 | </listitem> | |
311 | </varlistentry> | |
312 | <varlistentry> | |
313 | <term><literal>?</literal></term> | |
314 | <listitem> | |
315 | <para>Matches any single character.</para> | |
316 | </listitem> | |
317 | </varlistentry> | |
318 | <varlistentry> | |
319 | <term><literal>[]</literal></term> | |
320 | <listitem> | |
321 | <para>Matches any single character specified within the brackets. For | |
322 | example, the pattern string <literal>tty[SR]</literal> | |
323 | would match either <literal>ttyS</literal> or <literal>ttyR</literal>. | |
324 | Ranges are also supported via the <literal>-</literal> character. | |
325 | For example, to match on the range of all digits, the pattern | |
326 | <literal>[0-9]</literal> could be used. If the first character | |
327 | following the <literal>[</literal> is a <literal>!</literal>, | |
328 | any characters not enclosed are matched.</para> | |
329 | </listitem> | |
330 | </varlistentry> | |
331 | <varlistentry> | |
332 | <term><literal>|</literal></term> | |
333 | <listitem> | |
334 | <para>Separates alternative patterns. For example, the pattern string | |
335 | <literal>abc|x*</literal> would match either <literal>abc</literal> | |
336 | or <literal>x*</literal>.</para> | |
337 | </listitem> | |
338 | </varlistentry> | |
339 | </variablelist> | |
340 | ||
341 | <para>The following keys can get values assigned:</para> | |
342 | <variablelist class='udev-directives'> | |
343 | <varlistentry> | |
344 | <term><varname>NAME</varname></term> | |
345 | <listitem> | |
346 | <para>The name to use for a network interface. See | |
347 | <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
348 | for a higher-level mechanism for setting the interface name. | |
349 | The name of a device node cannot be changed by udev, only additional | |
350 | symlinks can be created.</para> | |
351 | </listitem> | |
352 | </varlistentry> | |
353 | ||
354 | <varlistentry> | |
355 | <term><varname>SYMLINK</varname></term> | |
356 | <listitem> | |
357 | <para>The name of a symlink targeting the node. Every matching rule adds | |
358 | this value to the list of symlinks to be created.</para> | |
359 | <para>The set of characters to name a symlink is limited. Allowed | |
360 | characters are <literal>0-9A-Za-z#+-.:=@_/</literal>, valid UTF-8 character | |
361 | sequences, and <literal>\x00</literal> hex encoding. All other | |
362 | characters are replaced by a <literal>_</literal> character.</para> | |
363 | <para>Multiple symlinks may be specified by separating the names by the | |
364 | space character. In case multiple devices claim the same name, the link | |
365 | always points to the device with the highest link_priority. If the current | |
366 | device goes away, the links are re-evaluated and the device with the | |
367 | next highest link_priority becomes the owner of the link. If no | |
368 | link_priority is specified, the order of the devices (and which one of | |
369 | them owns the link) is undefined.</para> | |
370 | <para>Symlink names must never conflict with the kernel's default device | |
371 | node names, as that would result in unpredictable behavior. | |
372 | </para> | |
373 | </listitem> | |
374 | </varlistentry> | |
375 | ||
376 | <varlistentry> | |
377 | <term><varname>OWNER</varname>, <varname>GROUP</varname>, <varname>MODE</varname></term> | |
378 | <listitem> | |
379 | <para>The permissions for the device node. Every specified value overrides | |
380 | the compiled-in default value.</para> | |
381 | </listitem> | |
382 | </varlistentry> | |
383 | ||
384 | <varlistentry> | |
385 | <term><varname>SECLABEL{<replaceable>module</replaceable>}</varname></term> | |
386 | <listitem> | |
387 | <para>Applies the specified Linux Security Module label to the device node.</para> | |
388 | </listitem> | |
389 | </varlistentry> | |
390 | ||
391 | <varlistentry> | |
392 | <term><varname>ATTR{<replaceable>key</replaceable>}</varname></term> | |
393 | <listitem> | |
394 | <para>The value that should be written to a sysfs attribute of the | |
395 | event device.</para> | |
396 | </listitem> | |
397 | </varlistentry> | |
398 | ||
399 | <varlistentry> | |
400 | <term><varname>SYSCTL{<replaceable>kernel parameter</replaceable>}</varname></term> | |
401 | <listitem> | |
402 | <para>The value that should be written to kernel parameter.</para> | |
403 | </listitem> | |
404 | </varlistentry> | |
405 | ||
406 | <varlistentry> | |
407 | <term><varname>ENV{<replaceable>key</replaceable>}</varname></term> | |
408 | <listitem> | |
409 | <para>Set a device property value. Property names with a leading <literal>.</literal> | |
410 | are neither stored in the database nor exported to events or | |
411 | external tools (run by, for example, the <varname>PROGRAM</varname> | |
412 | match key).</para> | |
413 | </listitem> | |
414 | </varlistentry> | |
415 | ||
416 | <varlistentry> | |
417 | <term><varname>TAG</varname></term> | |
418 | <listitem> | |
419 | <para>Attach a tag to a device. This is used to filter events for users | |
420 | of libudev's monitor functionality, or to enumerate a group of tagged | |
421 | devices. The implementation can only work efficiently if only a few | |
422 | tags are attached to a device. It is only meant to be used in | |
423 | contexts with specific device filter requirements, and not as a | |
424 | general-purpose flag. Excessive use might result in inefficient event | |
425 | handling.</para> | |
426 | </listitem> | |
427 | </varlistentry> | |
428 | ||
429 | <varlistentry> | |
430 | <term><varname>RUN{<replaceable>type</replaceable>}</varname></term> | |
431 | <listitem> | |
432 | <para>Add a program to the list of programs to be executed after | |
433 | processing all the rules for a specific event, depending on | |
434 | <literal>type</literal>:</para> | |
435 | <variablelist> | |
436 | <varlistentry> | |
437 | <term><literal>program</literal></term> | |
438 | <listitem> | |
439 | <para>Execute an external program specified as the assigned | |
440 | value. If no absolute path is given, the program is expected | |
441 | to live in <filename>/usr/lib/udev</filename>; otherwise, the | |
442 | absolute path must be specified.</para> | |
443 | <para>This is the default if no <replaceable>type</replaceable> | |
444 | is specified.</para> | |
445 | </listitem> | |
446 | </varlistentry> | |
447 | <varlistentry> | |
448 | <term><literal>builtin</literal></term> | |
449 | <listitem> | |
450 | <para>As <varname>program</varname>, but use one of the | |
451 | built-in programs rather than an external one.</para> | |
452 | </listitem> | |
453 | </varlistentry> | |
454 | </variablelist> | |
455 | <para>The program name and following arguments are separated by spaces. | |
456 | Single quotes can be used to specify arguments with spaces.</para> | |
457 | <para>This can only be used for very short-running foreground tasks. Running an | |
458 | event process for a long period of time may block all further events for | |
459 | this or a dependent device.</para> | |
460 | <para>Starting daemons or other long-running processes is not appropriate | |
461 | for udev; the forked processes, detached or not, will be unconditionally | |
462 | killed after the event handling has finished.</para> | |
463 | <para>Note that running programs that access the network or mount/unmount | |
464 | filesystems is not allowed inside of udev rules, due to the default sandbox | |
465 | that is enforced on <filename>systemd-udevd.service</filename>.</para> | |
466 | <para>Please also note that <literal>:=</literal> and <literal>=</literal> are clearing | |
467 | both, program and builtin commands.</para> | |
468 | <para>In order to activate long-running processes from udev rules, provide a service unit, and | |
469 | pull it in from a udev device using the <varname>SYSTEMD_WANTS</varname> device property. See | |
470 | <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
471 | for details.</para> | |
472 | </listitem> | |
473 | </varlistentry> | |
474 | ||
475 | <varlistentry> | |
476 | <term><varname>LABEL</varname></term> | |
477 | <listitem> | |
478 | <para>A named label to which a <varname>GOTO</varname> may jump.</para> | |
479 | </listitem> | |
480 | </varlistentry> | |
481 | ||
482 | <varlistentry> | |
483 | <term><varname>GOTO</varname></term> | |
484 | <listitem> | |
485 | <para>Jumps to the next <varname>LABEL</varname> with a matching name.</para> | |
486 | </listitem> | |
487 | </varlistentry> | |
488 | ||
489 | <varlistentry> | |
490 | <term><varname>IMPORT{<replaceable>type</replaceable>}</varname></term> | |
491 | <listitem> | |
492 | <para>Import a set of variables as device properties, | |
493 | depending on <literal>type</literal>:</para> | |
494 | <variablelist> | |
495 | <varlistentry> | |
496 | <term><literal>program</literal></term> | |
497 | <listitem> | |
498 | <para>Execute an external program specified as the assigned | |
499 | value and, if it returns successfully, | |
500 | import its output, which must be in environment key | |
501 | format. Path specification, command/argument separation, | |
502 | and quoting work like in <varname>RUN</varname>.</para> | |
503 | </listitem> | |
504 | </varlistentry> | |
505 | <varlistentry> | |
506 | <term><literal>builtin</literal></term> | |
507 | <listitem> | |
508 | <para>Similar to <literal>program</literal>, but use one of the | |
509 | built-in programs rather than an external one.</para> | |
510 | </listitem> | |
511 | </varlistentry> | |
512 | <varlistentry> | |
513 | <term><literal>file</literal></term> | |
514 | <listitem> | |
515 | <para>Import a text file specified as the assigned value, the content | |
516 | of which must be in environment key format.</para> | |
517 | </listitem> | |
518 | </varlistentry> | |
519 | <varlistentry> | |
520 | <term><literal>db</literal></term> | |
521 | <listitem> | |
522 | <para>Import a single property specified as the assigned value from the | |
523 | current device database. This works only if the database is already populated | |
524 | by an earlier event.</para> | |
525 | </listitem> | |
526 | </varlistentry> | |
527 | <varlistentry> | |
528 | <term><literal>cmdline</literal></term> | |
529 | <listitem> | |
530 | <para>Import a single property from the kernel command line. For simple flags | |
531 | the value of the property is set to <literal>1</literal>.</para> | |
532 | </listitem> | |
533 | </varlistentry> | |
534 | <varlistentry> | |
535 | <term><literal>parent</literal></term> | |
536 | <listitem> | |
537 | <para>Import the stored keys from the parent device by reading | |
538 | the database entry of the parent device. The value assigned to | |
539 | <option>IMPORT{parent}</option> is used as a filter of key names | |
540 | to import (with the same shell glob pattern matching used for | |
541 | comparisons).</para> | |
542 | </listitem> | |
543 | </varlistentry> | |
544 | </variablelist> | |
545 | <para>This can only be used for very short-running foreground tasks. For details | |
546 | see <option>RUN</option>.</para> | |
547 | </listitem> | |
548 | </varlistentry> | |
549 | ||
550 | <varlistentry> | |
551 | <term><varname>OPTIONS</varname></term> | |
552 | <listitem> | |
553 | <para>Rule and device options:</para> | |
554 | <variablelist class='udev-directives'> | |
555 | <varlistentry> | |
556 | <term><option>link_priority=<replaceable>value</replaceable></option></term> | |
557 | <listitem> | |
558 | <para>Specify the priority of the created symlinks. Devices with higher | |
559 | priorities overwrite existing symlinks of other devices. The default is 0.</para> | |
560 | </listitem> | |
561 | </varlistentry> | |
562 | <varlistentry> | |
563 | <term><option>string_escape=<replaceable>none|replace</replaceable></option></term> | |
564 | <listitem> | |
565 | <para>Usually, control and other possibly unsafe characters are replaced | |
566 | in strings used for device naming. The mode of replacement can be specified | |
567 | with this option.</para> | |
568 | </listitem> | |
569 | </varlistentry> | |
570 | <varlistentry> | |
571 | <term><option>static_node=</option></term> | |
572 | <listitem> | |
573 | <para>Apply the permissions specified in this rule to the | |
574 | static device node with the specified name. Also, for every | |
575 | tag specified in this rule, create a symlink | |
576 | in the directory | |
577 | <filename>/run/udev/static_node-tags/<replaceable>tag</replaceable></filename> | |
578 | pointing at the static device node with the specified name. | |
579 | Static device node creation is performed by systemd-tmpfiles | |
580 | before systemd-udevd is started. The static nodes might not | |
581 | have a corresponding kernel device; they are used to trigger | |
582 | automatic kernel module loading when they are accessed.</para> | |
583 | </listitem> | |
584 | </varlistentry> | |
585 | <varlistentry> | |
586 | <term><option>watch</option></term> | |
587 | <listitem> | |
588 | <para>Watch the device node with inotify; when the node is | |
589 | closed after being opened for writing, a change uevent is | |
590 | synthesized.</para> | |
591 | </listitem> | |
592 | </varlistentry> | |
593 | <varlistentry> | |
594 | <term><option>nowatch</option></term> | |
595 | <listitem> | |
596 | <para>Disable the watching of a device node with inotify.</para> | |
597 | </listitem> | |
598 | </varlistentry> | |
599 | <varlistentry> | |
600 | <term><option>db_persist</option></term> | |
601 | <listitem> | |
602 | <para>Set the flag (sticky bit) on the udev database entry | |
603 | of the event device. Device properties are then kept in the | |
604 | database even when | |
605 | <command>udevadm info --cleanup-db</command> is called. | |
606 | This option can be useful in certain cases | |
607 | (e.g. Device Mapper devices) for persisting device state | |
608 | on the transition from initramfs.</para> | |
609 | </listitem> | |
610 | </varlistentry> | |
611 | </variablelist> | |
612 | </listitem> | |
613 | </varlistentry> | |
614 | </variablelist> | |
615 | ||
616 | <para>The <varname>NAME</varname>, <varname>SYMLINK</varname>, | |
617 | <varname>PROGRAM</varname>, <varname>OWNER</varname>, | |
618 | <varname>GROUP</varname>, <varname>MODE</varname>, <varname>SECLABEL</varname>, | |
619 | and <varname>RUN</varname> fields support simple string substitutions. | |
620 | The <varname>RUN</varname> substitutions are performed after all rules | |
621 | have been processed, right before the program is executed, allowing for | |
622 | the use of device properties set by earlier matching rules. For all other | |
623 | fields, substitutions are performed while the individual rule is being | |
624 | processed. The available substitutions are:</para> | |
625 | <variablelist class='udev-directives'> | |
626 | <varlistentry> | |
627 | <term><option>$kernel</option>, <option>%k</option></term> | |
628 | <listitem> | |
629 | <para>The kernel name for this device.</para> | |
630 | </listitem> | |
631 | </varlistentry> | |
632 | ||
633 | <varlistentry> | |
634 | <term><option>$number</option>, <option>%n</option></term> | |
635 | <listitem> | |
636 | <para>The kernel number for this device. For example, | |
637 | <literal>sda3</literal> has kernel number <literal>3</literal>. | |
638 | </para> | |
639 | </listitem> | |
640 | </varlistentry> | |
641 | ||
642 | <varlistentry> | |
643 | <term><option>$devpath</option>, <option>%p</option></term> | |
644 | <listitem> | |
645 | <para>The devpath of the device.</para> | |
646 | </listitem> | |
647 | </varlistentry> | |
648 | ||
649 | <varlistentry> | |
650 | <term><option>$id</option>, <option>%b</option></term> | |
651 | <listitem> | |
652 | <para>The name of the device matched while searching the devpath | |
653 | upwards for <option>SUBSYSTEMS</option>, <option>KERNELS</option>, | |
654 | <option>DRIVERS</option>, and <option>ATTRS</option>. | |
655 | </para> | |
656 | </listitem> | |
657 | </varlistentry> | |
658 | ||
659 | <varlistentry> | |
660 | <term><option>$driver</option></term> | |
661 | <listitem> | |
662 | <para>The driver name of the device matched while searching the | |
663 | devpath upwards for <option>SUBSYSTEMS</option>, | |
664 | <option>KERNELS</option>, <option>DRIVERS</option>, and | |
665 | <option>ATTRS</option>. | |
666 | </para> | |
667 | </listitem> | |
668 | </varlistentry> | |
669 | ||
670 | <varlistentry> | |
671 | <term><option>$attr{<replaceable>file</replaceable>}</option>, <option>%s{<replaceable>file</replaceable>}</option></term> | |
672 | <listitem> | |
673 | <para>The value of a sysfs attribute found at the device where | |
674 | all keys of the rule have matched. If the matching device does not | |
675 | have such an attribute, and a previous <option>KERNELS</option>, | |
676 | <option>SUBSYSTEMS</option>, <option>DRIVERS</option>, or | |
677 | <option>ATTRS</option> test selected a parent device, then the | |
678 | attribute from that parent device is used. | |
679 | </para> | |
680 | <para>If the attribute is a symlink, the last element of the | |
681 | symlink target is returned as the value. | |
682 | </para> | |
683 | </listitem> | |
684 | </varlistentry> | |
685 | ||
686 | <varlistentry> | |
687 | <term><option>$env{<replaceable>key</replaceable>}</option>, <option>%E{<replaceable>key</replaceable>}</option></term> | |
688 | <listitem> | |
689 | <para>A device property value.</para> | |
690 | </listitem> | |
691 | </varlistentry> | |
692 | ||
693 | <varlistentry> | |
694 | <term><option>$major</option>, <option>%M</option></term> | |
695 | <listitem> | |
696 | <para>The kernel major number for the device.</para> | |
697 | </listitem> | |
698 | </varlistentry> | |
699 | ||
700 | <varlistentry> | |
701 | <term><option>$minor</option>, <option>%m</option></term> | |
702 | <listitem> | |
703 | <para>The kernel minor number for the device.</para> | |
704 | </listitem> | |
705 | </varlistentry> | |
706 | ||
707 | <varlistentry> | |
708 | <term><option>$result</option>, <option>%c</option></term> | |
709 | <listitem> | |
710 | <para>The string returned by the external program requested with | |
711 | <varname>PROGRAM</varname>. | |
712 | A single part of the string, separated by a space character, may be selected | |
713 | by specifying the part number as an attribute: <literal>%c{N}</literal>. | |
714 | If the number is followed by the <literal>+</literal> character, this part plus all remaining parts | |
715 | of the result string are substituted: <literal>%c{N+}</literal>.</para> | |
716 | </listitem> | |
717 | </varlistentry> | |
718 | ||
719 | <varlistentry> | |
720 | <term><option>$parent</option>, <option>%P</option></term> | |
721 | <listitem> | |
722 | <para>The node name of the parent device.</para> | |
723 | </listitem> | |
724 | </varlistentry> | |
725 | ||
726 | <varlistentry> | |
727 | <term><option>$name</option></term> | |
728 | <listitem> | |
729 | <para>The current name of the device. If not changed by a rule, it is the | |
730 | name of the kernel device.</para> | |
731 | </listitem> | |
732 | </varlistentry> | |
733 | ||
734 | <varlistentry> | |
735 | <term><option>$links</option></term> | |
736 | <listitem> | |
737 | <para>A space-separated list of the current symlinks. The value is | |
738 | only set during a remove event or if an earlier rule assigned a value.</para> | |
739 | </listitem> | |
740 | </varlistentry> | |
741 | ||
742 | <varlistentry> | |
743 | <term><option>$root</option>, <option>%r</option></term> | |
744 | <listitem> | |
745 | <para>The udev_root value.</para> | |
746 | </listitem> | |
747 | </varlistentry> | |
748 | ||
749 | <varlistentry> | |
750 | <term><option>$sys</option>, <option>%S</option></term> | |
751 | <listitem> | |
752 | <para>The sysfs mount point.</para> | |
753 | </listitem> | |
754 | </varlistentry> | |
755 | ||
756 | <varlistentry> | |
757 | <term><option>$devnode</option>, <option>%N</option></term> | |
758 | <listitem> | |
759 | <para>The name of the device node.</para> | |
760 | </listitem> | |
761 | </varlistentry> | |
762 | ||
763 | <varlistentry> | |
764 | <term><option>%%</option></term> | |
765 | <listitem> | |
766 | <para>The <literal>%</literal> character itself.</para> | |
767 | </listitem> | |
768 | </varlistentry> | |
769 | ||
770 | <varlistentry> | |
771 | <term><option>$$</option></term> | |
772 | <listitem> | |
773 | <para>The <literal>$</literal> character itself.</para> | |
774 | </listitem> | |
775 | </varlistentry> | |
776 | </variablelist> | |
777 | </refsect1> | |
778 | ||
779 | <refsect1> | |
780 | <title>See Also</title> | |
781 | <para> | |
782 | <citerefentry> | |
783 | <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum> | |
784 | </citerefentry>, | |
785 | <citerefentry> | |
786 | <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum> | |
787 | </citerefentry>, | |
788 | <citerefentry> | |
789 | <refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum> | |
790 | </citerefentry> | |
791 | </para> | |
792 | </refsect1> | |
793 | </refentry> |