kerne-command-line: introduce option 'systemd.restore_state'

When set to 0 this will stop tools like the backlight and rfkill tools to
restore state from previous boot. This is useful in case the stored state
is bogus to the extent that it is preventing you from resetting it (e.g.,
the backlight settings cause the screen to be off on boot on a system where
the backlight can not be adjusted directly from the keyboard).

7 files changed, 86 insertions, 2 deletions

diff --git a/man/kernel-command-line.xml b/man/kernel-command-line.xml
index abe68e5496..612dc28cd5 100644
--- a/man/kernel-command-line.xml
+++ b/man/kernel-command-line.xml
@@ -99,6 +99,21 @@
                         </varlistentry>
 
                         <varlistentry>
+                                <term><varname>systemd.restore_state=</varname></term>
+                                <listitem>
+                                        <para>Parameter understood by
+                                        several system tools to control
+                                        whether or not they should restore
+                                        system state from the previous boot.
+                                        For details, see
+                                        <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                                        and
+                                        <citerefentry><refentrytitle>systemd-rfkill@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+                                        </para>
+                                </listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><varname>quiet</varname></term>
                                 <listitem>
                                         <para>Parameter understood by
@@ -307,6 +322,8 @@
                           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                          <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                          <citerefentry><refentrytitle>systemd-rfkill@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                   </para>
         </refsect1>
 
diff --git a/man/systemd-backlight@.service.xml b/man/systemd-backlight@.service.xml
index 6d26d4b2ed..672fd05eb3 100644
--- a/man/systemd-backlight@.service.xml
+++ b/man/systemd-backlight@.service.xml
@@ -62,6 +62,26 @@
         </refsect1>
 
         <refsect1>
+                <title>Kernel Command Line</title>
+
+                <para><filename>systemd-backlight</filename> understands
+                the following kernel command line parameter:</para>
+
+                <variablelist class='kernel-commandline-options'>
+                        <varlistentry>
+                                <term><varname>systemd.restore_state=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. Defaults to
+                                <literal>1</literal>. If
+                                <literal>0</literal>, does not restore
+                                the backlight settings on boot. However,
+                                settings will still be stored on shutdown.
+                        </varlistentry>
+                </variablelist>
+        </refsect1>
+
+        <refsect1>
                 <title>See Also</title>
                 <para>
                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
diff --git a/man/systemd-rfkill@.service.xml b/man/systemd-rfkill@.service.xml
index b274cb818b..9ae834d5dd 100644
--- a/man/systemd-rfkill@.service.xml
+++ b/man/systemd-rfkill@.service.xml
@@ -62,6 +62,26 @@
         </refsect1>
 
         <refsect1>
+                <title>Kernel Command Line</title>
+
+                <para><filename>systemd-rfkill</filename> understands
+                the following kernel command line parameter:</para>
+
+                <variablelist class='kernel-commandline-options'>
+                        <varlistentry>
+                                <term><varname>systemd.restore_state=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. Defaults to
+                                <literal>1</literal>. If
+                                <literal>0</literal>, does not restore
+                                the rfkill settings on boot. However,
+                                settings will still be stored on shutdown.
+                        </varlistentry>
+                </variablelist>
+        </refsect1>
+
+        <refsect1>
                 <title>See Also</title>
                 <para>
                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
index e8cdad61ed..6c00b00d82 100644
--- a/src/backlight/backlight.c
+++ b/src/backlight/backlight.c
@@ -24,6 +24,7 @@
 #include "fileio.h"
 #include "libudev.h"
 #include "udev-util.h"
+#include "util.h"
 
 static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
         struct udev_device *parent;
@@ -290,7 +291,7 @@ int main(int argc, char *argv[]) {
          * device probing should be complete), so that the validity
          * check at boot time doesn't have to be reliable. */
 
-        if (streq(argv[1], "load")) {
+        if (streq(argv[1], "load") && restore_state()) {
                 _cleanup_free_ char *value = NULL;
 
                 if (!validate_device(udev, device))
diff --git a/src/rfkill/rfkill.c b/src/rfkill/rfkill.c
index 812cf408fb..b814e5c5fc 100644
--- a/src/rfkill/rfkill.c
+++ b/src/rfkill/rfkill.c
@@ -24,6 +24,7 @@
 #include "fileio.h"
 #include "libudev.h"
 #include "udev-util.h"
+#include "utils.h"
 
 int main(int argc, char *argv[]) {
         _cleanup_udev_unref_ struct udev *udev = NULL;
@@ -95,7 +96,7 @@ int main(int argc, char *argv[]) {
                 return EXIT_FAILURE;
         }
 
-        if (streq(argv[1], "load")) {
+        if (streq(argv[1], "load") && restore_state()) {
                 _cleanup_free_ char *value = NULL;
 
                 r = read_one_line_file(saved, &value);
diff --git a/src/shared/util.c b/src/shared/util.c
index 1822770304..d086fac7f8 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -76,6 +76,7 @@
 #include "device-nodes.h"
 #include "utf8.h"
 #include "gunicode.h"
+#include "virt.h"
 
 int saved_argc = 0;
 char **saved_argv = NULL;
@@ -5990,3 +5991,25 @@ int split_pair(const char *s, const char *sep, char **l, char **r) {
 
         return 0;
 }
+
+bool restore_state(void) {
+        _cleanup_free_ char *line;
+        char *w, *state;
+        int r;
+        size_t l;
+
+        if (detect_container(NULL) > 0)
+                return true;
+
+        r = read_one_line_file("/proc/cmdline", &line);
+        if (r < 0) {
+                log_warning("Failed to read /proc/cmdline, ignoring: %s", strerror(-r));
+                return 0;
+        }
+
+        FOREACH_WORD_QUOTED(w, l, line, state)
+                if (strneq(w, "systemd.restore_state=0", l))
+                        return false;
+
+        return true;
+}
diff --git a/src/shared/util.h b/src/shared/util.h
index 63cb4ac636..dc35b4d980 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -765,6 +765,8 @@ void parse_user_at_host(char *arg, char **user, char **host);
 
 int split_pair(const char *s, const char *sep, char **l, char **r);
 
+bool restore_state(void);
+
 /**
  * Normal qsort requires base to be nonnull. Here were require
  * that only if nmemb > 0.