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diff --git a/slackbook/html/essential-sysadmin-shutdown.html b/slackbook/html/essential-sysadmin-shutdown.html new file mode 100644 index 00000000..a97c78f6 --- /dev/null +++ b/slackbook/html/essential-sysadmin-shutdown.html @@ -0,0 +1,236 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org" /> +<title>Shutting Down Properly</title> +<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /> +<link rel="HOME" title="Slackware Linux Essentials" href="index.html" /> +<link rel="UP" title="Essential System Administration" href="essential-sysadmin.html" /> +<link rel="PREVIOUS" title="Users and Groups, the Hard Way" +href="essential-sysadmin-hardusers.html" /> +<link rel="NEXT" title="Basic Network Commands" href="basic-network-commands.html" /> +<link rel="STYLESHEET" type="text/css" href="docbook.css" /> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> +</head> +<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084" +alink="#0000FF"> +<div class="NAVHEADER"> +<table summary="Header navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<th colspan="3" align="center">Slackware Linux Essentials</th> +</tr> + +<tr> +<td width="10%" align="left" valign="bottom"><a href="essential-sysadmin-hardusers.html" +accesskey="P">Prev</a></td> +<td width="80%" align="center" valign="bottom">Chapter 12 Essential System +Administration</td> +<td width="10%" align="right" valign="bottom"><a href="basic-network-commands.html" +accesskey="N">Next</a></td> +</tr> +</table> + +<hr align="LEFT" width="100%" /> +</div> + +<div class="SECT1"> +<h1 class="SECT1"><a id="ESSENTIAL-SYSADMIN-SHUTDOWN" +name="ESSENTIAL-SYSADMIN-SHUTDOWN">12.3 Shutting Down Properly</a></h1> + +<p>It is very important that you shut down your system properly. Simply turning the power +off with the power switch can cause serious filesystem damage. While the system is on, +files are in use even if you aren't doing anything. Remember that there are many +processes running in the background all the time. These processes are managing the system +and keep a lot of files open. When the system's power is switched off, these files are +not closed properly and may become corrupted. Depending on what files become damaged, the +system might be rendered completely unusable! In any case, you'll have to go through a +long filesystem check procedure on the next reboot.</p> + +<div class="NOTE"> +<table class="NOTE" width="100%" border="0"> +<tr> +<td width="25" align="CENTER" valign="TOP"><img src="./imagelib/admon/note.png" +hspace="5" alt="Note" /></td> +<td align="LEFT" valign="TOP"> +<p>If you configured your system with a journalling filesystem, like ext3 or reiserfs, +you'll be partially protected from filesystem damage, and your filesystem check on reboot +will be shorter than if you had used a filesystem without journalling, like ext2. +However, this safety net is no excuse for improperly shutting down your system! A +journalling FS is meant to protect your files from events beyond your control, not from +your own laziness.</p> +</td> +</tr> +</table> +</div> + +<p>In any case, when you want to reboot or power down your computer, it is important to +do so properly. There are several ways of doing so; you can pick whichever one you think +is the most fun (or least amount of work). Since a shutdown and a reboot are similar +procedures, most of the ways for powering off the system can also be applied to +rebooting.</p> + +<p>The first method is through the <tt class="COMMAND">shutdown</tt>(8) program, and it +is probably the most popular. <tt class="COMMAND">shutdown</tt> can be used to reboot or +turn off the system at a given time, and can display a message to all the logged-in users +of the system telling them that the system is going down.</p> + +<p>The most basic use of shutdown to power down the computer is:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">shutdown -h now</kbd> +</pre> +</td> +</tr> +</table> + +<p>In this case, we are not going to send a custom message to the users; they will see +<tt class="COMMAND">shutdown</tt>'s default message. “<var +class="OPTION">now</var>” is the time that we want to shutdown, and the “<var +class="OPTION">-h</var>” means to halt the system. This is not a very friendly way +to run a multi-user system, but it works just fine on your home computer. A better method +on a multiuser system would be to give everyone a little advance warning:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">shutdown -h +60</kbd> +</pre> +</td> +</tr> +</table> + +<p>This would shutdown the system in one hour (60 minutes), which would be just fine on a +normal multiuser system. Vital systems should have their downtime scheduled far in +advance, and you should post warnings about the downtime in any appropriate locations +used for system notifications (email, bulletin board, <tt +class="FILENAME">/etc/motd</tt>, whatever).</p> + +<p>Rebooting the system uses the same command, but substitutes “<var +class="OPTION">-r</var>” for “<var class="OPTION">-h</var>”:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">shutdown -r now</kbd> +</pre> +</td> +</tr> +</table> + +<p>You can use same time notation with <tt class="COMMAND">shutdown -r</tt> that you +could with <tt class="COMMAND">shutdown -h</tt>. There are a lot of other things that you +can do with <tt class="COMMAND">shutdown</tt> to control when to halt or reboot the +machine; see the man page for more details.</p> + +<p>The second way of shutting down or powering off the computer is to use the <tt +class="COMMAND">halt</tt>(8) and <tt class="COMMAND">reboot</tt>(8) commands. As the +names indicate, <tt class="COMMAND">halt</tt> will immediately halt the operating system, +and <tt class="COMMAND">reboot</tt> will reboot the system. (<tt +class="COMMAND">reboot</tt> is actually just a symbolic link to <tt +class="COMMAND">halt</tt>.) They are invoked like so:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">halt</kbd> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">reboot</kbd> +</pre> +</td> +</tr> +</table> + +<p>A lower-level way to reboot or shutdown the system is to talk directly to <tt +class="COMMAND">init</tt>. All the other methods are simply convenient ways to talk to +<tt class="COMMAND">init</tt>, but you can directly tell it what to do using <tt +class="COMMAND">telinit</tt>(8) (note that it only has one “l”). Using <tt +class="COMMAND">telinit</tt> will tell <tt class="COMMAND">init</tt> what runlevel to +drop into, which will cause a special script to be run. This script will kill or spawn +processes as needed for that runlevel. This works for rebooting and shutting down because +both of those are special runlevels.</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">telinit 0</kbd> +</pre> +</td> +</tr> +</table> + +<p>Runlevel 0 is halt mode. Telling <tt class="COMMAND">init</tt> to enter runlevel 0 +will cause all processes to be killed off, the filesystems unmounted, and the machine to +be halted. This is a perfectly acceptable way to bring down the system. On many laptops +and modern desktop computers, this will also cause the machine to be turned off.</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">telinit 6</kbd> +</pre> +</td> +</tr> +</table> + +<p>Runlevel 6 is reboot mode. All processes will be killed off, the filesystems will be +unmounted, and the machine will be rebooted. This is a perfectly acceptable method of +rebooting the system.</p> + +<p>For the curious, when switching to runlevel 0 or 6, whether by using <tt +class="COMMAND">shutdown</tt>, <tt class="COMMAND">halt</tt>, or <tt +class="COMMAND">reboot</tt>, the script <tt class="FILENAME">/etc/rc.d/rc.6</tt> is run. +(The script <tt class="FILENAME">/etc/rc.d/rc.0</tt> is another symbolic link, to <tt +class="FILENAME">/etc/rc.d/rc.6</tt>.) You can customize this file to your tastes--but be +sure to test your changes carefully!</p> + +<p>There is one last method of rebooting the system. All the other methods require you to +be logged in as <tt class="USERNAME">root</tt>. However, it is possible to reboot the +machine even if you aren't root, provided that you have physical access to the keyboard. +Using <b class="KEYCAP">Control</b>+<b class="KEYCAP">Alt</b>+<b +class="KEYCAP">Delete</b> (the "three-fingered salute") will cause the machine to +immediately reboot. (Behind the scenes, the <tt class="COMMAND">shutdown</tt> command is +called for you when you use <b class="KEYCAP">Control</b>+<b class="KEYCAP">Alt</b>+<b +class="KEYCAP">Delete</b>.) The salute doesn't always work when using X Windows--you may +need to use <b class="KEYCAP">Control</b>+<b class="KEYCAP">Alt</b>+<b +class="KEYCAP">F1</b> (or another Function key) to switch to a non-X Windows terminal +before using it.</p> + +<p>Finally, the file that ultimately controls every aspect of startup and shutdown is the +<tt class="FILENAME">/etc/inittab</tt>(5) file. In general, you should not need to modify +this file, but it may give you insight into why some things work the way they do. As +always, see the man pages for further details.</p> +</div> + +<div class="NAVFOOTER"> +<hr align="LEFT" width="100%" /> +<table summary="Footer navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<td width="33%" align="left" valign="top"><a href="essential-sysadmin-hardusers.html" +accesskey="P">Prev</a></td> +<td width="34%" align="center" valign="top"><a href="index.html" +accesskey="H">Home</a></td> +<td width="33%" align="right" valign="top"><a href="basic-network-commands.html" +accesskey="N">Next</a></td> +</tr> + +<tr> +<td width="33%" align="left" valign="top">Users and Groups, the Hard Way</td> +<td width="34%" align="center" valign="top"><a href="essential-sysadmin.html" +accesskey="U">Up</a></td> +<td width="33%" align="right" valign="top">Basic Network Commands</td> +</tr> +</table> +</div> +</body> +</html> + |