journald: deprecate SplitMode=login (#3805)

In this mode, messages from processes which are not part of the session
land in the main journal file, and only output of processes which are
properly part of the session land in the user's journal. This is
confusing, in particular because systemd-coredump runs outside of the
login session.

"Deprecate" SplitMode=login by removing it from documentation, to
discourage people from using it.

NEWS

@@ -1,5 +1,12 @@
 systemd System and Service Manager
 
+CHANGES WITH 232 in spe
+
+        * Journald's SplitMode=login setting has been deprecated. It has been
+          removed from documentation, and it's use is discouraged. In a future
+          release it will be completely removed, and made equivalent to current
+          default of SplitMode=uid.
+
 CHANGES WITH 231:
 
         * In service units the various ExecXYZ= settings have been extended

man/journald.conf.xml

@@ -129,23 +129,15 @@
       <varlistentry>
         <term><varname>SplitMode=</varname></term>
 
-        <listitem><para>Controls whether to split up journal files per user. Split-up journal files are primarily
-        useful for access control: on UNIX/Linux access control is managed per file, and the journal daemon will assign
-        users read access to their journal files. This setting takes one of <literal>uid</literal>,
-        <literal>login</literal> or <literal>none</literal>. If <literal>uid</literal>, all regular users will get each
-        their own journal files regardless of whether their processes possess login sessions or not, however system
-        users will log into the system journal. If <literal>login</literal>, actually logged-in users will get each
-        their own journal files, but users without login session and system users will log into the system
-        journal. Note that in this mode, user code running outside of any login session will log into the system log
-        instead of the split-out user logs. Most importantly, this means that information about core dumps of user
-        processes collected via the
-        <citerefentry><refentrytitle>systemd-coredump</refentrytitle><manvolnum>8</manvolnum></citerefentry> subsystem
-        will end up in the system logs instead of the user logs, and thus not be accessible to the owning users. If
-        <literal>none</literal>, journal files are not split up by user and all messages are instead stored in the
-        single system journal. In this mode unprivileged users generally do not have access to their own log data. Note
-        that splitting up journal files by user is only available for journals stored persistently. If journals are
-        stored on volatile storage (see above), only a single journal file for all user IDs is kept. Defaults to
-        <literal>uid</literal>.</para></listitem>
+        <listitem><para>Controls whether to split up journal files per user, either <literal>uid</literal> or
+        <literal>none</literal>. Split journal files are primarily useful for access control: on UNIX/Linux access
+        control is managed per file, and the journal daemon will assign users read access to their journal files. If
+        <literal>uid</literal>, all regular users will each get their own journal files, and system users will log to
+        the system journal. If <literal>none</literal>, journal files are not split up by user and all messages are
+        instead stored in the single system journal. In this mode unprivileged users generally do not have access to
+        their own log data. Note that splitting up journal files by user is only available for journals stored
+        persistently. If journals are stored on volatile storage (see <varname>Storage=</varname> above), only a single
+        journal file is used. Defaults to <literal>uid</literal>.</para></listitem>
       </varlistentry>
 
       <varlistentry>

src/journal/journald-server.h

@@ -43,7 +43,7 @@ typedef enum Storage {
 
 typedef enum SplitMode {
         SPLIT_UID,
-        SPLIT_LOGIN,
+        SPLIT_LOGIN, /* deprecated */
         SPLIT_NONE,
         _SPLIT_MAX,
         _SPLIT_INVALID = -1