Index: usr.sbin/jail/command.c
===================================================================
--- usr.sbin/jail/command.c
+++ usr.sbin/jail/command.c
@@ -148,7 +148,8 @@
 		if (j->comstring == NULL || j->comstring->len == 0 ||
 		    (create_failed && (comparam == IP_EXEC_PRESTART ||
 		    comparam == IP_EXEC_CREATED || comparam == IP_EXEC_START ||
-		    comparam == IP_COMMAND || comparam == IP_EXEC_POSTSTART)))
+		    comparam == IP_COMMAND || comparam == IP_EXEC_POSTSTART ||
+		    comparam == IP_EXEC_PREPARE)))
 			continue;
 		switch (run_command(j)) {
 		case -1:
Index: usr.sbin/jail/config.c
===================================================================
--- usr.sbin/jail/config.c
+++ usr.sbin/jail/config.c
@@ -65,21 +65,24 @@
     [IP_ALLOW_DYING] =		{"allow.dying",		PF_INTERNAL | PF_BOOL},
     [IP_COMMAND] =		{"command",		PF_INTERNAL},
     [IP_DEPEND] =		{"depend",		PF_INTERNAL},
+    /* exec options */
     [IP_EXEC_CLEAN] =		{"exec.clean",		PF_INTERNAL | PF_BOOL},
     [IP_EXEC_CONSOLELOG] =	{"exec.consolelog",	PF_INTERNAL},
     [IP_EXEC_FIB] =		{"exec.fib",		PF_INTERNAL | PF_INT},
     [IP_EXEC_JAIL_USER] =	{"exec.jail_user",	PF_INTERNAL},
-    [IP_EXEC_POSTSTART] =	{"exec.poststart",	PF_INTERNAL},
-    [IP_EXEC_POSTSTOP] =	{"exec.poststop",	PF_INTERNAL},
-    [IP_EXEC_PRESTART] =	{"exec.prestart",	PF_INTERNAL},
-    [IP_EXEC_PRESTOP] =		{"exec.prestop",	PF_INTERNAL},
-    [IP_EXEC_CREATED] =		{"exec.created",	PF_INTERNAL},
-    [IP_EXEC_START] =		{"exec.start",		PF_INTERNAL},
-    [IP_EXEC_STOP] =		{"exec.stop",		PF_INTERNAL},
     [IP_EXEC_SYSTEM_JAIL_USER]=	{"exec.system_jail_user",
 							PF_INTERNAL | PF_BOOL},
     [IP_EXEC_SYSTEM_USER] =	{"exec.system_user",	PF_INTERNAL},
     [IP_EXEC_TIMEOUT] =		{"exec.timeout",	PF_INTERNAL | PF_INT},
+    /* exec commands */
+    [IP_EXEC_PREPARE] =		{"exec.prepare",	PF_INTERNAL},
+    [IP_EXEC_PRESTART] =	{"exec.prestart",	PF_INTERNAL},
+    [IP_EXEC_CREATED] =		{"exec.created",	PF_INTERNAL},
+    [IP_EXEC_START] =		{"exec.start",		PF_INTERNAL},
+    [IP_EXEC_POSTSTART] =	{"exec.poststart",	PF_INTERNAL},
+    [IP_EXEC_PRESTOP] =		{"exec.prestop",	PF_INTERNAL},
+    [IP_EXEC_STOP] =		{"exec.stop",		PF_INTERNAL},
+    [IP_EXEC_POSTSTOP] =	{"exec.poststop",	PF_INTERNAL},
 #if defined(INET) || defined(INET6)
     [IP_INTERFACE] =		{"interface",		PF_INTERNAL},
     [IP_IP_HOSTNAME] =		{"ip_hostname",		PF_INTERNAL | PF_BOOL},
Index: usr.sbin/jail/jail.8
===================================================================
--- usr.sbin/jail/jail.8
+++ usr.sbin/jail/jail.8
@@ -721,6 +721,11 @@
 .Pp
 The pseudo-parameters are:
 .Bl -tag -width indent
+.It Va exec.prepare
+Command(s) to run in the system environment to prepare a jail for creation.
+These commands are executed before assigning IP addresses and before mounting
+filesystems, so they may be used to create a new jail filesystem if it does
+not already exist.
 .It Va exec.prestart
 Command(s) to run in the system environment before a jail is created.
 .It Va exec.created
Index: usr.sbin/jail/jail.c
===================================================================
--- usr.sbin/jail/jail.c
+++ usr.sbin/jail/jail.c
@@ -87,6 +87,7 @@
 
 static const enum intparam startcommands[] = {
     IP__NULL,
+    IP_EXEC_PREPARE,
 #ifdef INET
     IP__IP4_IFADDR,
 #endif
Index: usr.sbin/jail/jailp.h
===================================================================
--- usr.sbin/jail/jailp.h
+++ usr.sbin/jail/jailp.h
@@ -81,20 +81,23 @@
 	IP_ALLOW_DYING,		/* Allow making changes to a dying jail */
 	IP_COMMAND,		/* Command run inside jail at creation */
 	IP_DEPEND,		/* Jail starts after (stops before) another */
+	/* exec options */
 	IP_EXEC_CLEAN,		/* Run commands in a clean environment */
 	IP_EXEC_CONSOLELOG,	/* Redirect optput for commands run in jail */
 	IP_EXEC_FIB,		/* Run jailed commands with this FIB */
 	IP_EXEC_JAIL_USER,	/* Run jailed commands as this user */
-	IP_EXEC_POSTSTART,	/* Commands run outside jail after creating */
-	IP_EXEC_POSTSTOP,	/* Commands run outside jail after removing */
+	IP_EXEC_SYSTEM_JAIL_USER,/* Get jail_user from system passwd file */
+	IP_EXEC_SYSTEM_USER,	/* Run non-jailed commands as this user */
+	IP_EXEC_TIMEOUT,	/* Time to wait for a command to complete */
+	/* exec commands */
+	IP_EXEC_PREPARE,	/* Commands run outside jail before addrs and mounting */
 	IP_EXEC_PRESTART,	/* Commands run outside jail before creating */
-	IP_EXEC_PRESTOP,	/* Commands run outside jail before removing */
 	IP_EXEC_CREATED,	/* Commands run outside jail right after it was started */
 	IP_EXEC_START,		/* Commands run inside jail on creation */
+	IP_EXEC_POSTSTART,	/* Commands run outside jail after creating */
+	IP_EXEC_PRESTOP,	/* Commands run outside jail before removing */
 	IP_EXEC_STOP,		/* Commands run inside jail on removal */
-	IP_EXEC_SYSTEM_JAIL_USER,/* Get jail_user from system passwd file */
-	IP_EXEC_SYSTEM_USER,	/* Run non-jailed commands as this user */
-	IP_EXEC_TIMEOUT,	/* Time to wait for a command to complete */
+	IP_EXEC_POSTSTOP,	/* Commands run outside jail after removing */
 #if defined(INET) || defined(INET6)
 	IP_INTERFACE,		/* Add IP addresses to this interface */
 	IP_IP_HOSTNAME,		/* Get jail IP address(es) from hostname */