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diff --git a/sag-0.6.1-www/Invisible/sag-0.6/node69.html b/sag-0.6.1-www/Invisible/sag-0.6/node69.html new file mode 100644 index 0000000..8ef46b2 --- /dev/null +++ b/sag-0.6.1-www/Invisible/sag-0.6/node69.html @@ -0,0 +1,136 @@ +<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> +<!--Converted with LaTeX2HTML 96.1-h (September 30, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds --> +<HTML> +<HEAD> +<TITLE>More about shutdowns</TITLE> +<META NAME="description" CONTENT="More about shutdowns"> +<META NAME="keywords" CONTENT="sag"> +<META NAME="resource-type" CONTENT="document"> +<META NAME="distribution" CONTENT="global"> +<LINK REL=STYLESHEET HREF="sag.css"> +</HEAD> +<BODY LANG="EN" > + <A NAME="tex2html1182" HREF="node70.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1180" HREF="node66.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1174" HREF="node68.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1184" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1185" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1183" HREF="node70.html">Rebooting</A> +<B>Up:</B> <A NAME="tex2html1181" HREF="node66.html">Boots And Shutdowns</A> +<B> Previous:</B> <A NAME="tex2html1175" HREF="node68.html">The boot process in </A> +<BR> <P> +<H1><A NAME="SECTION00730000000000000000">More about shutdowns</A></H1> +<P> + It is important to follow the correct procedures when you shut + down a Linux system. If you fail do so, your filesystems probably + will become trashed and the files probably will become scrambled. + This is because Linux has a disk cache that won't write things + to disk at once, but only at intervals. This greatly improves + performance but also means that if you just turn off the power + at a whim the cache may hold a lot of data and that what is on + the disk may not be a fully working filesystem (because only + some things have been written to the disk). +<A NAME="2036"> </A> +<A NAME="2037"> </A> +<A NAME="2038"> </A> +<A NAME="2039"> </A> +<P> + Another reason against just flipping the power switch is that + in a multi-tasking system there can be lots of things going on + in the background, and shutting the power can be quite + disastrous. By using the proper shutdown sequence, you ensure + that all background processes can save their data. +<A NAME="2040"> </A> +<P> + The command for properly shutting down a Linux system is + <tt>shutdown</tt><A NAME="2143"> </A>. It is usually used in one of two ways. +<A NAME="2042"> </A> +<P> + If you are running a system where you are the only user, the + usual way of using <tt>shutdown</tt><A NAME="2145"> </A> is to quit all running programs, + log out on all virtual consoles, log in as <tt>root</tt> on one + of them (or stay logged in as <tt>root</tt> if you already are, + but you should change to the root directory, to avoid problems + with unmounting), then give the command + <tt>shutdown -h now</tt><A NAME="2047"> </A> + (substitute <tt>now</tt> with a plus sign and a number in minutes + if you want a delay, though you usually don't on a single user + system). +<P> + Alternatively, if your system has many users, use the command + <tt>shutdown -h <i>+time message</i></tt>, where <i>time</i> + is the + time in minutes until the system is halted, and <i>message</i> + is a short explanation of why the system is shutting down. +<BLOCKQUOTE> <TT> +# shutdown -h +10 'We will install a new disk. System should <BR> +> be back on-line in three hours.' <BR> +# +</TT></BLOCKQUOTE> + This will warn everybody that the system will shut + down in ten minutes, and that they'd better get lost or lose + data. The warning is printed to + every terminal on which someone is logged in, including all + <tt>xterm</tt><A NAME="2147"> </A>s: +<BLOCKQUOTE> <TT> +Broadcast message from root (ttyp0) Wed Aug 2 01:03:25 1995... <BR> + <BR> +We will install a new disk. System should <BR> +be back on-line in three hours. <BR> +The system is going DOWN for system halt in 10 minutes !! +</TT></BLOCKQUOTE> + The warning is automatically repeated a few times before the + boot, with shorter and shorter intervals as the time runs out. +<A NAME="2057"> </A> +<P> + When the real shutting down starts after any + delays, all filesystems (except the root one) are unmounted, + user processes (if anybody is still logged in) are killed, + daemons are shut down, all filesystem are unmounted, + and generally everything settles down. + When that is done, <tt>init</tt><A NAME="2149"> </A> prints out a message that + you can power down the machine. Then, <EM>and only then</EM>, + should you move your fingers towards the power switch. +<A NAME="2060"> </A> +<P> + Sometimes, although rarely on any good system, it is + impossible to shut down properly. For instance, if the kernel + panics and crashes and burns and generally misbehaves, it + might be completely impossible to give any new commands, hence + shutting down properly is somewhat difficult, and just about + everything you can do is hope that nothing has been too + severely damaged and turn off the power. If the troubles are a + bit less severe (say, somebody hit your keyboard with + an axe), and the kernel and the <tt>update</tt><A NAME="2151"> </A> program still run + normally, it is probably a good idea to wait a couple of + minutes to give <tt>update</tt><A NAME="2153"> </A> a chance to flush the buffer + cache, and only cut the power after that. +<A NAME="2063"> </A> +<A NAME="2064"> </A> +<A NAME="2065"> </A> +<A NAME="2108"> </A> +<A NAME="2067"> </A> +<A NAME="2068"> </A> +<A NAME="2109"> </A> +<P> + Some people like to shut down using the command + <tt>sync</tt><A NAME="2155"> </A><A NAME="tex2html31" HREF="footnode.html#2110"><IMG ALIGN=BOTTOM ALT="gif" SRC="./foot_motif.gif"></A> + three times, waiting for the disk I/O to stop, then turn off + the power. If there are no running programs, this is about + equivalent to using <tt>shutdown</tt><A NAME="2159"> </A>. However, it does not + unmount any filesystems and this can lead to problems with the + ext2fs ``clean filesystem'' flag. The triple-sync method is + <em>not recommended</em>. +<A NAME="2074"> </A> +<P> + (In case you're wondering: the reason for <em>three</em> syncs is + that in the early days of UNIX, when the commands were + typed separately, that usually gave sufficient time for most + disk I/O to be finished.) +<P> +<HR><A NAME="tex2html1182" HREF="node70.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1180" HREF="node66.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1174" HREF="node68.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1184" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1185" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1183" HREF="node70.html">Rebooting</A> +<B>Up:</B> <A NAME="tex2html1181" HREF="node66.html">Boots And Shutdowns</A> +<B> Previous:</B> <A NAME="tex2html1175" HREF="node68.html">The boot process in </A> +<P><ADDRESS> +<I>Lars Wirzenius <BR> +Sat Nov 15 02:32:11 EET 1997</I> +</ADDRESS> +</BODY> +</HTML> |