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Update the troubleshooting section for systemd

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Eelco Dolstra 2013-01-09 13:43:57 +01:00
parent 19127aa416
commit b5e639dbb1
2 changed files with 46 additions and 36 deletions
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2
doc/manual/default.nix
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@ -59,7 +59,7 @@ in rec {
mkdir -p $dst/images/callouts
cp ${pkgs.docbook5_xsl}/xml/xsl/docbook/images/callouts/*.gif $dst/images/callouts/
cp ${./style.css} $dst/style.css
ensureDir $out/nix-support

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doc/manual/troubleshooting.xml
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@ -4,60 +4,70 @@
<title>Troubleshooting</title>
<section>
<title>Debugging the boot process</title>
<section><title>Boot problems</title>
<para>To get a Stage 1 shell (i.e., a shell in the initial ramdisk),
add <literal>debug1</literal> to the kernel command line. The shell
gets started before anything useful has been done. That is, no
modules have been loaded and no file systems have been mounted, except
for <filename>/proc</filename> and <filename>/sys</filename>.</para>
<para>If NixOS fails to boot, there are a number of kernel command
line parameters that may help you to identify or fix the issue. You
can add these parameters in the GRUB boot menu by pressing “e” to
modify the selected boot entry and editing the line starting with
<literal>linux</literal>. The following are some useful kernel command
line parameters that are recognised by the NixOS boot scripts or by
systemd:
<para>To get a Stage 2 shell (i.e., a shell in the actual root file
system), add <literal>debug2</literal> to the kernel command
line. This shell is started right after stage 1 calls the stage 2
<literal>init</literal> script, so the root file system is there but
no services have been started.</para>
<variablelist>
</section>
<varlistentry><term><literal>debug1</literal></term>
<listitem><para>Request an interactive shell in stage 1 of the
boot process (the initial ramdisk). The shell gets started before
anything useful has been done. That is, no modules have been
loaded and no file systems have been mounted, except for
<filename>/proc</filename> and
<filename>/sys</filename>.</para></listitem>
</varlistentry>
<varlistentry><term><literal>single</literal></term>
<listitem><para>Boot into rescue mode (a.k.a. single user mode).
This will cause systemd to start nothing but the unit
<literal>rescue.target</literal>, which runs
<command>sulogin</command> to prompt for the root password and
start a root login shell. Exiting the shell causes the system to
continue with the normal boot process.</para></listitem>
</varlistentry>
<varlistentry><term><literal>systemd.log_level=debug systemd.log_target=console</literal></term>
<listitem><para>Make systemd very verbose and send log messages to
the console instead of the journal.</para></listitem>
</varlistentry>
<section>
<title>Safe mode</title>
</variablelist>
<para>If the hardware autodetection (in
<filename>upstart-jobs/hardware-scan</filename>) causes problems, add
<literal>safemode</literal> to the kernel command line. This will
disable auto-loading of modules for your PCI devices. However, you
will probably need to explicitly add modules to
<option>boot.kernelModules</option> to get network support etc.</para>
For more parameters recognised by systemd, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
<para>If no login prompts or X11 login screens appear (e.g. due to
hanging dependencies), you can press Alt+ArrowUp. If you’re lucky,
this will start rescue mode (described above). (Also note that since
most units have a 90-second timeout before systemd gives up on them,
the <command>agetty</command> login prompts should appear eventually
unless something is very wrong.)</para>
</section>
<section>
<title>Maintenance mode</title>
<para>You can go to maintenance mode by doing
<para>You can enter rescue mode by running:
<screen>
$ shutdown now</screen>
$ systemctl rescue</screen>
This will eventually give you a single-user root shell.
To get out of maintenance mode, do
<screen>
$ initctl emit startup</screen>
</para>
This will eventually give you a single-user root shell. Systemd will
stop (almost) all system services. To get out of maintenance mode,
just exit from the rescue shell.</para>
</section>
</chapter>