Standard fenrir backgrounding and -d flags restored.

docs/fenrir.1

@@ -21,6 +21,9 @@ Run these commands from the checkout root after building
 \f[I]# Linux text console, with console and keyboard device access\f[R]
 sudo ./fenrir
 
+\f[I]# Linux console in the foreground (also use \-f with service managers)\f[R]
+sudo ./fenrir \-f
+
 \f[I]# X11 terminal, as your regular user\f[R]
 \&./fenrir \-x
 
@@ -28,8 +31,19 @@ sudo ./fenrir
 \&./fenrir \-x \-\-keyboard\-layout laptop
 .EE
 .PP
-Fenrir runs in the foreground.
-Press \f[B]Fenrir+Q\f[R] to quit.
+Console mode starts in the background by default.
+Add \f[CR]\-f\f[R] to keep it in the foreground, including under a
+service manager.
+The launcher returns after the reader initializes and reports startup
+failures in the launching terminal.
+Use \f[CR]\-\-debug\-file PATH\f[R] to retain diagnostics after
+detaching.
+Help, version, and configuration\-only commands always run in the
+foreground.
+.PP
+X11 mode (\f[CR]\-x\f[R]) always stays in the foreground because it owns
+the terminal and its child shell.
+Press \f[B]Fenrir+Q\f[R] to quit either mode.
 Run only one reader on a given Linux console.
 Separate X11 terminal instances can run at once.
 .PP
@@ -550,6 +564,13 @@ Purpose: Show usage and options
 Purpose: Print version and release channel
 .RE
 .IP \(bu 2
+\f[B]\-f\f[R]
+.RS 2
+.PP
+Purpose: Keep console mode in the foreground (always enabled with
+\f[CR]\-x\f[R])
+.RE
+.IP \(bu 2
 \f[B]\-x\f[R]
 .RS 2
 .PP