Add 'linux_mounts_enable' rc.conf(5) variable, to make it possible

to disable mounting Linux-specific filesystems under /compat/linux
when 'linux_enable' is set to YES.

Reviewed by:	netchild, ian (earlier version)
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D22320

libexec/rc/rc.conf

@@ -640,6 +640,8 @@ firstboot_sentinel="/firstboot"	# Scripts with "firstboot" keyword are run if
 			# the file can be deleted after the boot completes.
 sysvipc_enable="NO"	# Load System V IPC primitives at startup (or NO).
 linux_enable="NO"	# Linux binary compatibility loaded at startup (or NO).
+linux_mounts_enable="YES" # If linux_enable is set to YES, mount Linux-specific
+			# filesystems at startup.
 clear_tmp_enable="NO"	# Clear /tmp at startup.
 clear_tmp_X="YES" 	# Clear and recreate X11-related directories in /tmp
 ldconfig_insecure="NO"	# Set to YES to disable ldconfig security checks

libexec/rc/rc.d/linux

@@ -46,12 +46,14 @@ linux_start()
 		sysctl kern.elf32.fallback_brand=3 > /dev/null
 	fi
 
-	_emul_path="/compat/linux"
-	mount -o nocover -t linprocfs linprocfs "${_emul_path}/proc"
-	mount -o nocover -t linsysfs linsysfs "${_emul_path}/sys"
-	mount -o nocover -t devfs devfs "${_emul_path}/dev"
-	mount -o nocover -t fdescfs fdescfs "${_emul_path}/dev/fd"
-	mount -o nocover,mode=1777 -t tmpfs tmpfs "${_emul_path}/dev/shm"
+	if checkyesno linux_mounts_enable; then 
+		_emul_path="/compat/linux"
+		mount -o nocover -t linprocfs linprocfs "${_emul_path}/proc"
+		mount -o nocover -t linsysfs linsysfs "${_emul_path}/sys"
+		mount -o nocover -t devfs devfs "${_emul_path}/dev"
+		mount -o nocover -t fdescfs fdescfs "${_emul_path}/dev/fd"
+		mount -o nocover,mode=1777 -t tmpfs tmpfs "${_emul_path}/dev/shm"
+	fi
 }
 
 load_rc_config $name