Index: head/lib/libc/gen/sysctl.c
===================================================================
--- head/lib/libc/gen/sysctl.c
+++ head/lib/libc/gen/sysctl.c
@@ -87,6 +87,15 @@
 		if (oldp != NULL)
 			memmove(oldp, _PATH_STDPATH, sizeof(_PATH_STDPATH));
 		return (0);
+	case USER_LOCALBASE:
+		if (oldp && orig_oldlen < sizeof(_PATH_LOCALBASE)) {
+			errno = ENOMEM;
+			return -1;
+		}
+		*oldlenp = sizeof(_PATH_LOCALBASE);
+		if (oldp != NULL)
+			memmove(oldp, _PATH_LOCALBASE, sizeof(_PATH_LOCALBASE));
+		return(0);
 	}
 
 	if (oldp && *oldlenp < sizeof(int)) {
Index: head/sys/kern/kern_mib.c
===================================================================
--- head/sys/kern/kern_mib.c
+++ head/sys/kern/kern_mib.c
@@ -652,6 +652,8 @@
     SYSCTL_NULL_INT_PTR, 0, "Min Maximum number of streams a process may have open at one time");
 SYSCTL_INT(_user, USER_TZNAME_MAX, tzname_max, CTLFLAG_RD,
     SYSCTL_NULL_INT_PTR, 0, "Min Maximum number of types supported for timezone names");
+SYSCTL_STRING(_user, USER_LOCALBASE, localbase, CTLFLAG_RD,
+    "", 0, "Prefix used to install and locate add-on packages");
 
 #include <sys/vnode.h>
 SYSCTL_INT(_debug_sizeof, OID_AUTO, vnode, CTLFLAG_RD,
Index: head/sys/sys/sysctl.h
===================================================================
--- head/sys/sys/sysctl.h
+++ head/sys/sys/sysctl.h
@@ -1070,6 +1070,7 @@
 #define	USER_POSIX2_UPE		18	/* int: POSIX2_UPE */
 #define	USER_STREAM_MAX		19	/* int: POSIX2_STREAM_MAX */
 #define	USER_TZNAME_MAX		20	/* int: POSIX2_TZNAME_MAX */
+#define	USER_LOCALBASE		21	/* string: _PATH_LOCALBASE */
 
 #define	CTL_P1003_1B_ASYNCHRONOUS_IO		1	/* boolean */
 #define	CTL_P1003_1B_MAPPED_FILES		2	/* boolean */