Document boot_cdrom, boot_multicons, and boot_serial.

Reduce diffs between help.common and loader(8).
Mention that boot_userconfig is currently a no-op.

sys/boot/common/help.common

@@ -143,28 +143,53 @@
 	Instructs the kernel to prompt the user for the name of the root device
 	when the kernel is booted.
 
+################################################################################
+# Tset Sboot_cdrom DMount root file system from CD-ROM
+
+	set boot_cdrom
+
+	Instructs the kernel to try to mount the root file system from CD-ROM.
+
 ################################################################################
 # Tset Sboot_ddb DDrop to the kernel debugger (DDB)
 
 	set boot_ddb
 
 	Instructs the kernel to start in the DDB debugger, rather than
-	proceeding to initialise when booted.
+	proceeding to initialize when booted.
 
 ################################################################################
-# Tset Sboot_gdb DSelect gdb-remote mode
+# Tset Sboot_gdb DSelect gdb-remote mode for the kernel debugger
 
 	set boot_gdb
 
 	Selects gdb-remote mode for the kernel debugger by default.
 
+################################################################################
+# Tset Sboot_multicons DUse multiple consoles
+
+	set boot_multicons
+
+	Enables multiple console support in the kernel early on boot.
+	In a running system, console configuration can be manipulated
+	by the conscontrol(8) utility.
+
+################################################################################
+# Tset Sboot_serial DUse serial console
+
+	set boot_serial
+
+	Force the use of a serial console even when an internal console
+	is present.
+
 ################################################################################
 # Tset Sboot_single DStart system in single-user mode
 
 	set boot_single
 
-	Prevents the kernel from initiating a multi-user startup, single-user
+	Prevents the kernel from initiating a multi-user startup; instead,
-	mode will be entered when the kernel has finished device probes.
+	a single-user mode will be entered when the kernel has finished
+	device probes.
 
 ################################################################################
 # Tset Sboot_verbose DVerbose boot messages

sys/boot/common/loader.8

@@ -332,17 +332,30 @@ will be processed normally, defaulting to 10 seconds delay.
 .It Va boot_askname
 Instructs the kernel to prompt the user for the name of the root device
 when the kernel is booted.
+.It Va boot_cdrom
+Instructs the kernel to try to mount the root file system from CD-ROM.
 .It Va boot_ddb
 Instructs the kernel to start in the DDB debugger, rather than
 proceeding to initialize when booted.
 .It Va boot_gdb
 Selects gdb-remote mode for the kernel debugger by default.
+.It Va boot_multicons
+Enables multiple console support in the kernel early on boot.
+In a running system, console configuration can be manipulated
+by the
+.Xr conscontrol 8
+utility.
+.It Va boot_serial
+Force the use of a serial console even when an internal console
+is present.
 .It Va boot_single
-Prevents the kernel from initiating a multi-user startup; instead single-user
+Prevents the kernel from initiating a multi-user startup; instead,
-mode will be entered when the kernel has finished device probing.
+a single-user mode will be entered when the kernel has finished
+device probing.
 .It Va boot_userconfig
 Requests that the kernel's interactive device configuration program
 be run when the kernel is booted.
+Currently a no-op.
 .It Va boot_verbose
 Setting this variable causes extra debugging information to be printed
 by the kernel during the boot phase.

sys/boot/forth/loader.conf

@@ -62,10 +62,14 @@ module_path="/boot/modules"	# Set the module search path
 			# The following boot_ variables are enabled
 			# by setting them to any value.
 #boot_askname=""	# Prompt the user for the name of the root device
+#boot_cdrom=""		# Attempt to mount root file system from CD-ROM
 #boot_ddb=""		# Instructs the kernel to start in the DDB debugger
 #boot_gdb=""		# Selects gdb-remote mode for the kernel debugger
+#boot_multicons=""	# Use multiple consoles
+#boot_serial=""		# Use serial console
 #boot_single=""		# Start system in single-user mode
-#boot_userconfig=""	# Run kernel's interactive device configuration program
+#boot_userconfig=""	# Run kernel's interactive device configuration program;
+			# currently a no-op
 #boot_verbose=""	# Causes extra debugging information to be printed
 #init_path="/sbin/init:/sbin/oinit:/sbin/init.bak:/stand/sysinstall"
 			# Sets the list of init candidates

sys/boot/i386/loader/help.i386

@@ -49,7 +49,7 @@
 	set boot_userconfig
 
 	Requests that the kernel's interactive device configuration program
-	be run when the kernel is booted.
+	be run when the kernel is booted.  Currently a no-op.
 
 ################################################################################
 # Tset Sroot_disk_unit DForce the root disk unit number.

sys/boot/pc98/loader/help.pc98

@@ -31,7 +31,7 @@
 	set boot_userconfig
 
 	Requests that the kernel's interactive device configuration program
-	be run when the kernel is booted.
+	be run when the kernel is booted.  Currently a no-op.
 
 ################################################################################
 # Tset Sroot_disk_unit DForce the root disk unit number.