man: clarify NotifyAccess overriding (#3620)

Type=notify has a magic overriding case where a NotifyAccess=none
is turned into a NotifyAccess=main for sanity purposes.
This makes docs more clear about such behavior:
https://github.com/systemd/systemd/blob/2787d83c28b7565ea6f80737170514e5e6186917/src/core/service.c#L650:L651

diff --git a/man/systemd.service.xml b/man/systemd.service.xml
index 6e969ab..70f12b2 100644 (file)
--- a/man/systemd.service.xml
+++ b/man/systemd.service.xml
@@ -202,8 +202,9 @@
         notification message has been sent. If this option is used,
         <varname>NotifyAccess=</varname> (see below) should be set to
         open access to the notification socket provided by systemd. If
-        <varname>NotifyAccess=</varname> is not set, it will be
-        implicitly set to <option>main</option>. Note that currently
+        <varname>NotifyAccess=</varname> is missing or set to
+        <option>none</option>, it will be forcibly set to
+        <option>main</option>. Note that currently
         <varname>Type=</varname><option>notify</option> will not work
         if used in combination with
         <varname>PrivateNetwork=</varname><option>yes</option>.</para>