+ <div class="entry">
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/How_is_booting_into_runlevel_1_different_from_single_user_boots_.html">How is booting into runlevel 1 different from single user boots?</a></div>
+ <div class="date">2011-08-04 12:40</div>
+ <div class="body">
+<p>Wouter Verhelst have some
+<a href="http://grep.be/blog/en/retorts/pere_kubuntu_boot">interesting
+pcomments and opinions</a> on my blog post on
+<a href="http://people.skolelinux.org/pere/blog/What_should_start_from__etc_rcS_d__in_Debian____almost_nothing.html">the
+need to clean up /etc/rcS.d/ in Debian</a> and my blog post about
+<a href="http://people.skolelinux.org/pere/blog/What_is_missing_in_the_Debian_desktop__or_why_my_parents_use_Kubuntu.html">the
+default KDE desktop in Debian</a>. I only have time to address one
+small piece of his comment now, and though it best to address the
+misunderstanding he bring forward:</p>
+
+<p><blockquote>
+Currently, a system admin has four options: [...] boot to a
+single-user system (by adding 'single' to the kernel command line;
+this runs rcS and rc1 scripts)
+</blockquote></p>
+
+<p>This make me believe Wouter believe booting into single user mode
+and booting into runlevel 1 is the same. I am not surprised he
+believe this, because it would make sense and is a quite sensible
+thing to believe. But because the boot in Debian is slightly broken,
+runlevel 1 do not work properly and it isn't the same as single user
+mode. I'll try to explain what is actually happing, but it is a bit
+hard to explain.</p>
+
+<p>Single user mode is defined like this in /etc/inittab:
+"<tt>~~:S:wait:/sbin/sulogin</tt>". This means the only thing that is
+executed in single user mode in sulogin. Single user mode is a boot
+state "between" the runlevels, and when booting into single user mode,
+only the scripts in /etc/rcS.d/ are executed before the init process
+enters the single user state. When switching to runlevel 1, the state
+is in fact not ending in runlevel 1, but it passes through runlevel 1
+and end up in the single user mode (see /etc/rc1.d/S03single, which
+runs "init -t1 S" to switch to single user mode at the end of runlevel
+1. It is confusing that the 'S' (single user) init mode is not the
+mode enabled by /etc/rcS.d/ (which is more like the initial boot
+mode).</p>
+
+<p>This summary might make it clearer. When booting for the first
+time into single user mode, the following commands are executed:
+"<tt>/etc/init.d/rc S; /sbin/sulogin</tt>". When booting into
+runlevel 1, the following commands are executed: "<tt>/etc/init.d/rc
+S; /etc/init.d/rc 1; /sbin/sulogin</tt>". A problem show up when
+trying to continue after visiting single user mode. Not all services
+are started again as they should, causing the machine to end up in an
+unpredicatble state. This is why Debian admins recommend rebooting
+after visiting single user mode.</p>
+
+<p>A similar problem with runlevel 1 is caused by the amount of
+scripts executed from /etc/rcS.d/. When switching from say runlevel 2
+to runlevel 1, the services started from /etc/rcS.d/ are not properly
+stopped when passing through the scripts in /etc/rc1.d/, and not
+started again when switching away from runlevel 1 to the runlevels
+2-5. I believe the problem is best fixed by moving all the scripts
+out of /etc/rcS.d/ that are not <strong>required</strong> to get a
+functioning single user mode during boot.</p>
+
+<p>I have spent several years investigating the Debian boot system,
+and discovered this problem a few years ago. I suspect it originates
+from when sysvinit was introduced into Debian, a long time ago.</p>
+</div>
+ <div class="tags">
+
+
+
+ Tags: <a href="http://people.skolelinux.org/pere/blog/tags/bootsystem">bootsystem</a>, <a href="http://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>.
+
+ </div>
+ </div>
+ <div class="padding"></div>
+
<div class="entry">
<div class="title"><a href="http://people.skolelinux.org/pere/blog/Fint_at_milit__ret_ikke_ble_aktivisert_22__juli.html">Fint at militæret ikke ble aktivisert 22. juli</a></div>
<div class="date">2011-08-02 09:35</div>
</div>
<div class="padding"></div>
- <div class="entry">
- <div class="title"><a href="http://people.skolelinux.org/pere/blog/Free_Software_vs__proprietary_softare___.html">Free Software vs. proprietary softare...</a></div>
- <div class="date">2011-06-20 12:50</div>
- <div class="body">
-<p>Reading
-<a href="http://blog.thingiverse.com/2011/06/20/open-source-vs-closed-source-eulas/">the
-thingiverse blog</a>, I came across two highlights of interesting
-parts of the
-<a href="http://wiki.blender.org/index.php/Autodesk_EULA">Autodesk</a>
-and
-<a href="http://blog.makezine.com/archive/2011/06/things-you-cant-do-with-the-microsoft-kinect-sdk.html">Microsoft
-Kinect</a> End User License Agreements (EULAs), which illustrates
-quite well why I stay away from software with EULAs. Whenever I take
-the time to read their content, the terms are simply unacceptable.</p>
-</div>
- <div class="tags">
-
-
-
- Tags: <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/opphavsrett">opphavsrett</a>.
-
- </div>
- </div>
- <div class="padding"></div>
-
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