Bug#774233: systemd shell

[Niels Thykier <niels@thykier.net>]

Control: tags -1 patch

On 2014-12-30 17:10, Antoine Beaupré wrote:
> And actually, maybe it should be a subsection like 4.1.4.1 that would be
> refered to by 5.5...
> 

Hi,

Thanks for reporting this.

The attached patch attempts to cover a basic 4.1.4.2 section for
describing how to obtain a shell under systemd if booting fails.
Admittedly, it lacks a reference from 5.5, but that should be fairly
trivial once the contents of 4.1.4.2 is in place.

A review would be greatly appreciated.

Thanks,
~Niels


diff --git a/en/upgrading.dbk b/en/upgrading.dbk
index 4bbc849..394b60f 100644
--- a/en/upgrading.dbk
+++ b/en/upgrading.dbk
@@ -189,7 +189,32 @@ course you will also need to fix the underlying problem and regenerate the
 initrd so the next boot won't fail again.
 </para>
 </section>
-
+<section id="recovery-shell-systemd">
+  <title>Debug shell during boot using systemd</title>
+  <para>
+    In case the boot fails under systemd, it is possible to obtain a
+    debug root shell by changing the kernel command line.  If the
+    basic boot succeeds, but some of the services fails to start, it
+    may be useful to add <literal>systemd.unit=rescue.target</literal>
+    to the kernel parameters.
+  </para>
+  <para>
+    Otherwise, the kernel parameter
+    <literal>systemd.unit=emergency.target</literal> will provide you
+    with an root shell at the earliest possible point.  However, this
+    is done before mounting the root file system with read-write
+    permissions.  You will have to do that manually with:
+  </para>
+  <screen>
+mount -o remount,rw /
+  </screen>
+  <para>
+    For more information on debugging a broken boot under systemd
+    can be found in the <ulink
+    url="http://freedesktop.org/wiki/Software/systemd/Debugging/";>
+    Diagnosing Boot Problems</ulink> article.
+  </para>
+</section>
 </section>
 
 <section id="upgrade-preparations">