Attachment 17534 Details for Bug 31821 – file.diff

[patch] file.diff

file.diff (text/plain), 2.83 KB, created by Michael W Lucas on 2001-11-07 14:10:00 UTC

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Creator: Michael W Lucas

Created: 2001-11-07 14:10:00 UTC

Size: 2.83 KB

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obsolete

>*** en_US.ISO8859-1/books/faq/book.sgml-dist	Mon Nov  5 10:49:36 2001
>--- en_US.ISO8859-1/books/faq/book.sgml	Wed Nov  7 09:05:22 2001
>***************
>*** 5869,5874 ****
>--- 5869,5921 ----
>        </qandaentry>
>  
>        <qandaentry>
>+         <question id="du-vs-df">
>+           <para>The <command>du</command> and <command>df</command>
>+             commands show different amounts of disk space available?
>+             What's going on?</para>
>+         </question>
>+ 
>+         <answer>
>+           <para>You need to understand what <command>du</command> and
>+             <command>df</command> really do.  <command>du</command>
>+             shows how much of the disk is designated <emphasis>used by
>+             files</emphasis>.  <command>df</command> shows how much of
>+             the disk is designated <emphasis>free</emphasis>.  While
>+             they seem to be opposite, that isn't exactly true.</para>
>+ 
>+           <para>When a program has a file open, and you delete the
>+             file, it isn't really deleted until the program releases
>+             the file.  You can see this easily enough with a program
>+             such as <command>more</command>.  If you delete a file
>+             while using <command>more</command> on it,
>+             <command>more</command> doesn't immediately choke and
>+             complain that it cannot view the file.  You cannot access
>+             the file from anywhere except that <command>more</command>
>+             window.  If the file is large enough,
>+             <command>df</command> will show that it is gone.  The
>+             space the file took up is now designated free.
>+             <command>du</command> will show that it is still there, as
>+             the space the file uses is still technically in use.  Once
>+             you end the <command>more</command> session,
>+             <command>du</command> and <command>df</command> will
>+             agree.</para>
>+ 
>+           <para>Note that softupdates can delay the freeing of disk
>+             space; you might need to wait up to 30 seconds for the
>+             change to be visible!</para>
>+ 
>+           <para>This situation is common on web servers.  Many people
>+             set up a FreeBSD web server and forget to rotate the log
>+             files.  The access log fills up <filename>/var</filename>.
>+             The new administrator deletes the file, but the system
>+             still complains that the partition is full.  Stopping and
>+             restarting the web server program would free the file,
>+             allowing the system to release the disk space.  To prevent
>+             this from happening, set up &man.newsyslog.8;.</para>
>+         </answer>
>+       </qandaentry>
>+ 
>+       <qandaentry>
>          <question id="add-swap-space">
>            <para>How can I add more swap space?</para>
>          </question>

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