manager: add ManagerEnvironment configuration setting

This is useful for various variables that modify process behaviour. This makes
it easy to set it for pid1 without touching the kernel command line. Even for
the *user manager* this also can be convenient for the unprivileged user, who
cannot modify user@.service definition.

Variables that could be set like this include $SD_EVENT_PROFILE_DELAYS,
$SYSTEMD_FALLBACK_HOSTNAME, $SYSTEMD_MEMPOOL, $SYSTMED_RDRAND, etc.

1 files changed, 18 insertions, 5 deletions

diff --git a/man/systemd-system.conf.xml b/man/systemd-system.conf.xml
index 0811e1909e..d39928ec23 100644
--- a/man/systemd-system.conf.xml
+++ b/man/systemd-system.conf.xml
@@ -323,11 +323,10 @@
       <varlistentry>
         <term><varname>DefaultEnvironment=</varname></term>
 
-        <listitem><para>Sets manager environment variables passed to
-        all executed processes. Takes a space-separated list of
-        variable assignments. See
-        <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
-        for details about environment variables.</para>
+        <listitem><para>Configures environment variables passed to all executed processes. Takes a
+        space-separated list of variable assignments. See <citerefentry
+        project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
+        details about environment variables.</para>
 
         <para>Example:
 
@@ -340,6 +339,20 @@
       </varlistentry>
 
       <varlistentry>
+        <term><varname>ManagerEnvironment=</varname></term>
+
+        <listitem><para>Takes the same arguments as <varname>DefaultEnvironment=</varname>, see above. Sets
+        environment variables just for the manager process itself. These variables are not inherited by
+        processes spawned by the service manager, use <varname>DefaultEnvironment=</varname> for that. Note
+        that these variables are merged into the existing environment block. In particular, in case of the
+        system manager, this includes variables set by the kernel based on the kernel command line.</para>
+
+        <para>Setting environment variables for the manager process may be useful to modify its behaviour.
+        See <ulink url="https://systemd.io/ENVIRONMENT">ENVIRONMENT</ulink> for a descriptions of some
+        variables understood by <command>systemd</command>.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
         <term><varname>DefaultCPUAccounting=</varname></term>
         <term><varname>DefaultBlockIOAccounting=</varname></term>
         <term><varname>DefaultMemoryAccounting=</varname></term>