source: chapter09/usage.xml@ 103ded2

Last change on this file since 103ded2 was 103ded2, checked in by William Harrington <kb0iic@…>, 9 months ago

Clarify SysV run levels.
Update the meaning of run level 2.

Add some clarifying remarks about run levels 0 and 6 (halt and reboot).

  • Property mode set to 100644
File size: 29.0 KB
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 <!ENTITY site SYSTEM "../appendices/">
6 %general-entities;
9<sect1 id="ch-config-usage" revision="sysv">
10 <?dbhtml filename="usage.html"?>
12 <title>System V Bootscript Usage and Configuration</title>
14 <indexterm zone="ch-config-usage">
15 <primary sortas="a-Bootscripts">Bootscripts</primary>
16 <secondary>usage</secondary>
17 </indexterm>
19 <sect2>
20 <title>How Do the System V Bootscripts Work?</title>
22 <para>Linux uses a special booting facility named SysVinit that is based on a
23 concept of <emphasis>run-levels</emphasis>. It can be quite different from one
24 system to another, so it cannot be assumed that because things worked in one
25 particular Linux distribution, they should work the same in LFS too. LFS has its
26 own way of doing things, but it respects generally accepted standards.</para>
28 <para>SysVinit (which will be referred to as <quote>init</quote> from now on)
29 works using a run-levels scheme. There are seven (numbered 0 to 6) run-levels
30 (actually, there are more run-levels, but they are for special cases and are
31 generally not used. See <filename>init(8)</filename> for more details), and
32 each one of those corresponds to the actions the computer is supposed to
33 perform when it starts up. The default run-level is 3. Here are the
34 descriptions of the different run-levels as they are implemented:</para>
36<literallayout>0: halt the computer
371: single-user mode
382: reserved for customization, otherwise does the same as 3
393: multi-user mode with networking
404: reserved for customization, otherwise does the same as 3
415: same as 4, it is usually used for GUI login (like X's <command>xdm</command> or KDE's <command>kdm</command>)
426: reboot the computer</literallayout>
44 <note>
45 <para>
46 Classically, run level 2 above was defined as
47 "multi-user mode without networking", but this was only the case
48 many years ago when multiple users could log into a system connected via
49 serial ports. In today's environment it makes no sense and
50 we designate it now as "reserved".
51 </para>
52 </note>
54 </sect2>
56 <sect2 id="conf-sysvinit" role="configuration">
57 <title>Configuring Sysvinit</title>
59 <indexterm zone="conf-sysvinit">
60 <primary sortas="a-Sysvinit">Sysvinit</primary>
61 <secondary>configuring</secondary>
62 </indexterm>
64 <indexterm zone="conf-sysvinit">
65 <primary sortas="e-/etc/inittab">/etc/inittab</primary>
66 </indexterm>
68 <para>During the kernel initialization, the first program that is run
69 is either specified on the command line or, by default
70 <command>init</command>. This program reads the initialization file
71 <filename>/etc/inittab</filename>. Create this file with:</para>
73<screen><userinput>cat &gt; /etc/inittab &lt;&lt; "EOF"
74<literal># Begin /etc/inittab
78si::sysinit:/etc/rc.d/init.d/rc S
80l0:0:wait:/etc/rc.d/init.d/rc 0
81l1:S1:wait:/etc/rc.d/init.d/rc 1
82l2:2:wait:/etc/rc.d/init.d/rc 2
83l3:3:wait:/etc/rc.d/init.d/rc 3
84l4:4:wait:/etc/rc.d/init.d/rc 4
85l5:5:wait:/etc/rc.d/init.d/rc 5
86l6:6:wait:/etc/rc.d/init.d/rc 6
88ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
931:2345:respawn:/sbin/agetty --noclear tty1 9600
942:2345:respawn:/sbin/agetty tty2 9600
953:2345:respawn:/sbin/agetty tty3 9600
964:2345:respawn:/sbin/agetty tty4 9600
975:2345:respawn:/sbin/agetty tty5 9600
986:2345:respawn:/sbin/agetty tty6 9600
100# End /etc/inittab</literal>
103 <para>An explanation of this initialization file is in the man page for
104 <emphasis>inittab</emphasis>. For LFS, the key command that is run is
105 <command>rc</command>. The initialization file above will instruct
106 <command>rc</command> to run all the scripts starting with an S in the
107 <filename class="directory">/etc/rc.d/rcS.d</filename> directory
108 followed by all the scripts starting with an S in the <filename
109 class="directory">/etc/rc.d/rc?.d</filename> directory where the question
110 mark is specified by the initdefault value.</para>
112 <para>As a convenience, the <command>rc</command> script reads a library of
113 functions in <filename class="directory">/lib/lsb/init-functions</filename>.
114 This library also reads an optional configuration file,
115 <filename>/etc/sysconfig/</filename>. Any of the system
116 configuration file parameters described in subsequent sections can be
117 alternatively placed in this file allowing consolidation of all system
118 parameters in this one file.</para>
120 <para>As a debugging convenience, the functions script also logs all output
121 to <filename>/run/var/bootlog</filename>. Since the <filename
122 class="directory">/run</filename> directory is a tmpfs, this file is not
123 persistent across boots, however it is appended to the more permanent file
124 <filename>/var/log/boot.log</filename> at the end of the boot process.</para>
126 <sect3 id="init-levels" >
127 <title>Changing Run Levels</title>
129 <para>Changing run-levels is done with <command>init
130 <replaceable>&lt;runlevel&gt;</replaceable></command>, where
131 <replaceable>&lt;runlevel&gt;</replaceable> is the target run-level. For example, to
132 reboot the computer, a user could issue the <command>init 6</command> command,
133 which is an alias for the <command>reboot</command> command. Likewise,
134 <command>init 0</command> is an alias for the <command>halt</command>
135 command.</para>
137 <para>There are a number of directories under <filename
138 class="directory">/etc/rc.d</filename> that look like <filename
139 class="directory">rc?.d</filename> (where ? is the number of the run-level) and
140 <filename class="directory">rcS.d</filename>, all containing a number of
141 symbolic links. Some begin with a <emphasis>K</emphasis>, the others begin with
142 an <emphasis>S</emphasis>, and all of them have two numbers following the
143 initial letter. The K means to stop (kill) a service and the S means to start a
144 service. The numbers determine the order in which the scripts are run, from 00
145 to 99&mdash;the lower the number the earlier it gets executed. When
146 <command>init</command> switches to another run-level, the appropriate services
147 are either started or stopped, depending on the runlevel chosen.</para>
149 <para>The real scripts are in <filename
150 class="directory">/etc/rc.d/init.d</filename>. They do the actual work, and
151 the symlinks all point to them. K links and S links point to
152 the same script in <filename class="directory">/etc/rc.d/init.d</filename>.
153 This is because the scripts can be called with different parameters like
154 <parameter>start</parameter>, <parameter>stop</parameter>,
155 <parameter>restart</parameter>, <parameter>reload</parameter>, and
156 <parameter>status</parameter>. When a K link is encountered, the appropriate
157 script is run with the <parameter>stop</parameter> argument. When an S link
158 is encountered, the appropriate script is run with the
159 <parameter>start</parameter> argument.</para>
161 <para>There is one exception to this explanation. Links that start
162 with an <emphasis>S</emphasis> in the <filename
163 class="directory">rc0.d</filename> and <filename
164 class="directory">rc6.d</filename> directories will not cause anything
165 to be started. They will be called with the parameter
166 <parameter>stop</parameter> to stop something. The logic behind this
167 is that when a user is going to reboot or halt the system, nothing
168 needs to be started, but the order of shutdown needs to be controlled.
169 For these run levels, all <emphasis>K</emphasis> prefixed scripts will be
170 run before any <emphasis>S</emphasis> prefixed scripts are run with the
171 <parameter>stop</parameter> parameter.
172 </para>
174 <para>These are descriptions of what the arguments make the scripts
175 do:</para>
177 <variablelist>
179 <varlistentry>
180 <term><parameter>start</parameter></term>
181 <listitem>
182 <para>The service is started.</para>
183 </listitem>
184 </varlistentry>
186 <varlistentry>
187 <term><parameter>stop</parameter></term>
188 <listitem>
189 <para>The service is stopped.</para>
190 </listitem>
191 </varlistentry>
193 <varlistentry>
194 <term><parameter>restart</parameter></term>
195 <listitem>
196 <para>The service is stopped and then started again.</para>
197 </listitem>
198 </varlistentry>
200 <varlistentry>
201 <term><parameter>reload</parameter></term>
202 <listitem>
203 <para>The configuration of the service is updated.
204 This is used after the configuration file of a service was modified, when
205 the service does not need to be restarted.</para>
206 </listitem>
207 </varlistentry>
209 <varlistentry>
210 <term><parameter>status</parameter></term>
211 <listitem>
212 <para>Tells if the service is running and with which PIDs.</para>
213 </listitem>
214 </varlistentry>
216 </variablelist>
218 <para>Feel free to modify the way the boot process works (after all,
219 it is your own LFS system). The files given here are an example of how
220 it can be done.</para>
222 </sect3>
223 </sect2>
225 <sect2>
226 <title>Udev Bootscripts</title>
228 <para>The <filename>/etc/rc.d/init.d/udev</filename> initscript starts
229 <command>udevd</command>, triggers any "coldplug" devices that have
230 already been created by the kernel and waits for any rules to complete.
231 The script also unsets the uevent handler from the default of
232 <filename>/sbin/hotplug </filename>. This is done because the kernel no
233 longer needs to call out to an external binary. Instead
234 <command>udevd</command> will listen on a netlink socket for uevents that
235 the kernel raises.</para>
237 <para>The <command>/etc/rc.d/init.d/udev_retry</command> initscript takes
238 care of re-triggering events for subsystems whose rules may rely on
239 filesystems that are not mounted until the <command>mountfs</command>
240 script is run (in particular, <filename class="directory">/usr</filename>
241 and <filename class="directory">/var</filename> may cause this). This
242 script runs after the <command>mountfs</command> script, so those rules
243 (if re-triggered) should succeed the second time around. It is
244 configured from the <filename>/etc/sysconfig/udev_retry</filename> file;
245 any words in this file other than comments are considered subsystem names
246 to trigger at retry time. To find the subsystem of a device, use
247 <command>udevadm info --attribute-walk &lt;device&gt;</command> where
248 &lt;device&gt; is an absolute path in /dev or /sys such as /dev/sr0 or
249 /sys/class/rtc.</para>
251 <para>For information on kernel module loading and udev, see
252 <xref linkend="module-loading"/>.</para>
253 </sect2>
255 <sect2 id="ch-config-clock">
256 <title>Configuring the System Clock</title>
258 <indexterm zone="ch-config-clock">
259 <primary sortas="d-setclock">setclock</primary>
260 <secondary>configuring</secondary></indexterm>
262 <para>The <command>setclock</command> script reads the time from the hardware
263 clock, also known as the BIOS or the Complementary Metal Oxide Semiconductor
264 (CMOS) clock. If the hardware clock is set to UTC, this script will convert the
265 hardware clock's time to the local time using the
266 <filename>/etc/localtime</filename> file (which tells the
267 <command>hwclock</command> program which timezone to use). There is no
268 way to detect whether or not the hardware clock is set to UTC, so this
269 needs to be configured manually.</para>
271 <para>The <command>setclock</command> program is run via
272 <application>udev</application> when the kernel detects the hardware
273 capability upon boot. It can also be run manually with the stop parameter to
274 store the system time to the CMOS clock.</para>
276 <para>If you cannot remember whether or not the hardware clock is set to UTC,
277 find out by running the <userinput>hwclock --localtime --show</userinput>
278 command. This will display what the current time is according to the hardware
279 clock. If this time matches whatever your watch says, then the hardware clock is
280 set to local time. If the output from <command>hwclock</command> is not local
281 time, chances are it is set to UTC time. Verify this by adding or subtracting
282 the proper amount of hours for the timezone to the time shown by
283 <command>hwclock</command>. For example, if you are currently in the MST
284 timezone, which is also known as GMT -0700, add seven hours to the local
285 time.</para>
287 <para>Change the value of the <envar>UTC</envar> variable below
288 to a value of <parameter>0</parameter> (zero) if the hardware clock
289 is <emphasis>NOT</emphasis> set to UTC time.</para>
291 <para>Create a new file <filename>/etc/sysconfig/clock</filename> by running
292 the following:</para>
294<screen><userinput>cat &gt; /etc/sysconfig/clock &lt;&lt; "EOF"
295<literal># Begin /etc/sysconfig/clock
299# Set this to any options you might need to give to hwclock,
300# such as machine hardware clock type for Alphas.
303# End /etc/sysconfig/clock</literal>
306 <para>A good hint explaining how to deal with time on LFS is available
307 at <ulink url="&hints-root;time.txt"/>. It explains issues such as
308 time zones, UTC, and the <envar>TZ</envar> environment variable.</para>
310 <note><para>The CLOCKPARAMS and UTC parameters may also be set
311 in the <filename>/etc/sysconfig/</filename> file.</para></note>
313 </sect2>
315 <sect2 id="ch-config-console">
316 <?dbhtml filename="console.html"?>
318 <title>Configuring the Linux Console</title>
320 <indexterm zone="ch-config-console">
321 <primary sortas="d-console">console</primary>
322 <secondary>configuring</secondary>
323 </indexterm>
325 <para>This section discusses how to configure the <command>console</command>
326 bootscript that sets up the keyboard map, console font, and console kernel log
327 level. If non-ASCII characters (e.g., the copyright sign, the British pound
328 sign and Euro symbol) will not be used and the keyboard is a U.S. one, much
329 of this section can be skipped. Without the configuration file, (or
330 equivalent settings in <filename></filename>), the
331 <command>console</command> bootscript will do nothing.</para>
333 <para>The <command>console</command> script reads the
334 <filename>/etc/sysconfig/console</filename> file for configuration
335 information. Decide which keymap and screen font will be used. Various
336 language-specific HOWTOs can also help with this, see <ulink
337 url=""/>. If still in
338 doubt, look in the <filename class="directory">/usr/share/keymaps</filename>
339 and <filename class="directory">/usr/share/consolefonts</filename> directories
340 for valid keymaps and screen fonts. Read <filename>loadkeys(1)</filename> and
341 <filename>setfont(8)</filename> manual pages to determine the correct
342 arguments for these programs.</para>
344 <para>The <filename>/etc/sysconfig/console</filename> file should contain lines
345 of the form: VARIABLE="value". The following variables are recognized:</para>
346 <variablelist>
348 <varlistentry>
349 <term>LOGLEVEL</term>
350 <listitem>
351 <para>This variable specifies the log level for kernel messages sent
352 to the console as set by <command>dmesg -n</command>. Valid levels are
353 from "1" (no messages) to "8". The default level is "7".</para>
354 </listitem>
355 </varlistentry>
357 <varlistentry>
358 <term>KEYMAP</term>
359 <listitem>
360 <para>This variable specifies the arguments for the
361 <command>loadkeys</command> program, typically, the name of keymap
362 to load, e.g., <quote>it</quote>. If this variable is not set, the
363 bootscript will not run the <command>loadkeys</command> program,
364 and the default kernel keymap will be used. Note that a few keymaps
365 have multiple versions with the same name (cz and its variants in
366 qwerty/ and qwertz/, es in olpc/ and qwerty/, and trf in fgGIod/ and
367 qwerty/). In these cases the parent directory should also be specified
368 (e.g. qwerty/es) to ensure the proper keymap is loaded.
369 </para>
370 </listitem>
371 </varlistentry>
373 <varlistentry>
374 <term>KEYMAP_CORRECTIONS</term>
375 <listitem>
376 <para>This (rarely used) variable
377 specifies the arguments for the second call to the
378 <command>loadkeys</command> program. This is useful if the stock keymap
379 is not completely satisfactory and a small adjustment has to be made. E.g.,
380 to include the Euro sign into a keymap that normally doesn't have it,
381 set this variable to <quote>euro2</quote>.</para>
382 </listitem>
383 </varlistentry>
385 <varlistentry>
386 <term>FONT</term>
387 <listitem>
388 <para>This variable specifies the arguments for the
389 <command>setfont</command> program. Typically, this includes the font
390 name, <quote>-m</quote>, and the name of the application character
391 map to load. E.g., in order to load the <quote>lat1-16</quote> font
392 together with the <quote>8859-1</quote> application character map
393 (as it is appropriate in the USA),
394 <!-- because of the copyright sign -->
395 set this variable to <quote>lat1-16 -m 8859-1</quote>.
396 In UTF-8 mode, the kernel uses the application character map for
397 conversion of composed 8-bit key codes in the keymap to UTF-8, and thus
398 the argument of the "-m" parameter should be set to the encoding of the
399 composed key codes in the keymap.</para>
401 </listitem>
402 </varlistentry>
404 <varlistentry>
405 <term>UNICODE</term>
406 <listitem>
407 <para>Set this variable to <quote>1</quote>, <quote>yes</quote> or
408 <quote>true</quote> in order to put the
409 console into UTF-8 mode. This is useful in UTF-8 based locales and
410 harmful otherwise.</para>
411 </listitem>
412 </varlistentry>
414 <varlistentry>
415 <term>LEGACY_CHARSET</term>
416 <listitem>
417 <para>For many keyboard layouts, there is no stock Unicode keymap in
418 the Kbd package. The <command>console</command> bootscript will
419 convert an available keymap to UTF-8 on the fly if this variable is
420 set to the encoding of the available non-UTF-8 keymap.</para>
421 </listitem>
422 </varlistentry>
424 </variablelist>
426 <para>Some examples:</para>
428 <itemizedlist>
430 <listitem>
431 <para>For a non-Unicode setup, only the KEYMAP and FONT variables are
432 generally needed. E.g., for a Polish setup, one would use:</para>
433<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
434<literal># Begin /etc/sysconfig/console
437FONT="lat2a-16 -m 8859-2"
439# End /etc/sysconfig/console</literal>
441 </listitem>
443 <listitem>
444 <para>As mentioned above, it is sometimes necessary to adjust a
445 stock keymap slightly. The following example adds the Euro symbol to the
446 German keymap:</para>
448<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
449<literal># Begin /etc/sysconfig/console
453FONT="lat0-16 -m 8859-15"
456# End /etc/sysconfig/console</literal>
458 </listitem>
460 <listitem>
461 <para>The following is a Unicode-enabled example for Bulgarian, where a
462 stock UTF-8 keymap exists:</para>
463<!-- This is what is used by jhalfs for creating the console file: whenever
464 you change the following, please inform the jhalfs maintainer(s). -->
465<screen><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
466<literal># Begin /etc/sysconfig/console
472# End /etc/sysconfig/console</literal>
474 </listitem>
476 <listitem>
477 <para>Due to the use of a 512-glyph LatArCyrHeb-16 font in the previous
478 example, bright colors are no longer available on the Linux console unless
479 a framebuffer is used. If one wants to have bright colors without a
480 framebuffer and can live without characters not belonging to his language,
481 it is still possible to use a language-specific 256-glyph font, as
482 illustrated below:</para>
484<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
485<literal># Begin /etc/sysconfig/console
491# End /etc/sysconfig/console</literal>
493 </listitem>
495 <listitem>
496 <para>The following example illustrates keymap autoconversion from
497 ISO-8859-15 to UTF-8 and enabling dead keys in Unicode mode:</para>
499<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
500<literal># Begin /etc/sysconfig/console
506FONT="LatArCyrHeb-16 -m 8859-15"
508# End /etc/sysconfig/console</literal>
510 </listitem>
512 <listitem>
513 <para>Some keymaps have dead keys (i.e., keys that don't produce a
514 character by themselves, but put an accent on the character produced
515 by the next key) or define composition rules (such as: <quote>press
516 Ctrl+. A E to get &AElig;</quote> in the default keymap).
517 Linux-&linux-version; interprets dead keys and composition rules in the
518 keymap correctly only when the source characters to be composed together
519 are not multibyte. This deficiency doesn't affect keymaps for European
520 languages, because there accents are added to unaccented ASCII
521 characters, or two ASCII characters are composed together. However, in
522 UTF-8 mode it is a problem; e.g., for the Greek language, where one
523 sometimes needs to put an accent on the letter <quote>alpha</quote>.
524 The solution is either to avoid the use of UTF-8, or to install the
525 X window system that doesn't have this limitation in its input
526 handling.</para>
527 </listitem>
529 <listitem>
530 <para>For Chinese, Japanese, Korean, and some other languages, the Linux
531 console cannot be configured to display the needed characters. Users
532 who need such languages should install the X Window System, fonts that
533 cover the necessary character ranges, and the proper input method (e.g.,
534 SCIM, supports a wide variety of languages).</para>
535 </listitem>
537 </itemizedlist>
539 <!-- Added because folks keep posting their console file with X questions
540 to blfs-support list -->
541 <note>
542 <para>The <filename>/etc/sysconfig/console</filename> file only controls
543 the Linux text console localization. It has nothing to do with setting
544 the proper keyboard layout and terminal fonts in the X Window System, with
545 ssh sessions, or with a serial console. In such situations, limitations
546 mentioned in the last two list items above do not apply.</para>
547 </note>
549 </sect2>
551 <sect2 id="ch-config-createfiles">
552 <title>Creating Files at Boot</title>
554 <indexterm zone="ch-config-createfiles">
555 <primary sortas="d-createfiles">File creation at boot</primary>
556 <secondary>configuring</secondary>
557 </indexterm>
559 <para>At times, it is desirable to create files at boot time. For instance,
560 the <filename class="directory">/tmp/.ICE-unix</filename> directory
561 is often needed. This can be done by creating an entry in the
562 <filename>/etc/sysconfig/createfiles</filename> configuration script.
563 The format of this file is embedded in the comments of the default
564 configuration file.</para>
565 </sect2>
567 <sect2 id="ch-config-sysklogd">
568 <title>Configuring the sysklogd Script</title>
570 <indexterm zone="ch-config-sysklogd">
571 <primary sortas="d-sysklogd">sysklogd</primary>
572 <secondary>configuring</secondary>
573 </indexterm>
575 <para>The <filename>sysklogd</filename> script invokes the
576 <command>syslogd</command> program as a part of System V initialization. The
577 <parameter>-m 0</parameter> option turns off the periodic timestamp mark that
578 <command>syslogd</command> writes to the log files every 20 minutes by
579 default. If you want to turn on this periodic timestamp mark, edit
580 <filename>/etc/sysconfig/</filename> and define the variable
581 SYSKLOGD_PARMS to the desired value. For instance, to remove all parameters,
582 set the variable to a null value:</para>
584<screen role="nodump">SYSKLOGD_PARMS=</screen>
586 <para>See <userinput>man syslogd</userinput> for more options.</para>
588 </sect2>
590 <sect2 id="ch-config-site">
591 <title>The File</title>
593 <indexterm zone="ch-config-site">
594 <primary sortas=""></primary>
595 </indexterm>
597 <para>The optional <filename>/etc/sysconfig/</filename> file contains
598 settings that are automatically set for each SystemV boot script. It can
599 alternatively set the values specified in the <filename>hostname</filename>,
600 <filename>console</filename>, and <filename>clock</filename> files in the
601 <filename class='directory'>/etc/sysconfig/</filename> directory. If the
602 associated variables are present in both these separate files and
603 <filename></filename>, the values in the script specific files have
604 precedence. </para>
606 <para><filename></filename> also contains parameters that can
607 customize other aspects of the boot process. Setting the IPROMPT variable
608 will enable selective running of bootscripts. Other options are described
609 in the file comments. The default version of the file is as follows:</para>
611 <!-- Use role to fix a pdf generation problem -->
612 <screen role="auto">&site;</screen>
614 <sect3>
615 <title>Customizing the Boot and Shutdown Scripts</title>
617 <para>The LFS boot scripts boot and shut down a system in a fairly
618 efficient manner, but there are a few tweaks that you can make in the
619 file to improve speed even more and to adjust messages according
620 to your preferences. To do this, adjust the settings in
621 the <filename>/etc/sysconfig/</filename> file above.</para>
623 <itemizedlist>
625 <listitem><para>During the boot script <filename>udev</filename>, there is
626 a call to <command>udev settle</command> that requires some time to
627 complete. This time may or may not be required depending on devices present
628 in the system. If you only have simple partitions and a single ethernet
629 card, the boot process will probably not need to wait for this command. To
630 skip it, set the variable OMIT_UDEV_SETTLE=y.</para></listitem>
632 <listitem><para>The boot script <filename>udev_retry</filename> also runs
633 <command>udev settle</command> by default. This command is only needed by
634 default if the <filename class='directory'>/var</filename> directory is
635 separately mounted. This is because the clock needs the file
636 <filename>/var/lib/hwclock/adjtime</filename>. Other customizations may
637 also need to wait for udev to complete, but in many installations it is not
638 needed. Skip the command by setting the variable OMIT_UDEV_RETRY_SETTLE=y.
639 </para></listitem>
641 <listitem><para>By default, the file system checks are silent. This can
642 appear to be a delay during the bootup process. To turn on the
643 <command>fsck</command> output, set the variable VERBOSE_FSCK=y.
644 </para></listitem>
646 <listitem><para>When rebooting, you may want to skip the filesystem check,
647 <command>fsck</command>, completely. To do this, either create the file
648 <filename>/fastboot</filename> or reboot the system with the command
649 <command>/sbin/shutdown -f -r now</command>. On the other hand, you can
650 force all file systems to be checked by creating
651 <filename>/forcefsck</filename> or running <command>shutdown</command> with
652 the <parameter>-F</parameter> parameter instead of <parameter>-f</parameter>.
653 </para>
655 <para>Setting the variable FASTBOOT=y will disable <command>fsck</command>
656 during the boot process until it is removed. This is not recommended
657 on a permanent basis.</para></listitem>
659 <listitem><para>Normally, all files in the <filename
660 class='directory'>/tmp</filename> directory are deleted at boot time.
661 Depending on the number of files or directories present, this can cause a
662 noticeable delay in the boot process. To skip removing these files set the
663 variable SKIPTMPCLEAN=y.</para></listitem>
665 <listitem><para>During shutdown, the <command>init</command> program sends
666 a TERM signal to each program it has started (e.g. agetty), waits for a set
667 time (default 3 seconds), and sends each process a KILL signal and waits
668 again. This process is repeated in the <command>sendsignals</command>
669 script for any processes that are not shut down by their own scripts. The
670 delay for <command>init</command> can be set by passing a parameter. For
671 example to remove the delay in <command>init</command>, pass the -t0
672 parameter when shutting down or rebooting (e.g. <command>/sbin/shutdown
673 -t0 -r now</command>). The delay for the <command>sendsignals</command>
674 script can be skipped by setting the parameter
675 KILLDELAY=0.</para></listitem>
677 </itemizedlist>
679 </sect3>
680 </sect2>
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