Index: sys/compat/linux/linux_emul.c
===================================================================
--- sys/compat/linux/linux_emul.c
+++ sys/compat/linux/linux_emul.c
@@ -316,6 +316,7 @@
 			/*
 			 * We are switching the process to Linux emulator.
 			 */
+			linux_xchroot(td);
 			linux_proc_init(td, td, 0);
 
 			/*
Index: sys/compat/linux/linux_mib.h
===================================================================
--- sys/compat/linux/linux_mib.h
+++ sys/compat/linux/linux_mib.h
@@ -67,5 +67,6 @@
 extern int linux_ignore_ip_recverr;
 extern int linux_preserve_vstatus;
 extern bool linux_map_sched_prio;
+extern bool linux_autochroot;
 
 #endif /* _LINUX_MIB_H_ */
Index: sys/compat/linux/linux_mib.c
===================================================================
--- sys/compat/linux/linux_mib.c
+++ sys/compat/linux/linux_mib.c
@@ -85,6 +85,10 @@
     &linux_map_sched_prio, 0, "Map scheduler priorities to Linux priorities "
     "(not POSIX compliant)");
 
+bool linux_autochroot = false;
+SYSCTL_BOOL(_compat_linux, OID_AUTO, autochroot, CTLFLAG_RWTUN,
+    &linux_autochroot, 0, "XXX");
+
 static int	linux_set_osname(struct thread *td, char *osname);
 static int	linux_set_osrelease(struct thread *td, char *osrelease);
 static int	linux_set_oss_version(struct thread *td, int oss_version);
Index: sys/compat/linux/linux_util.h
===================================================================
--- sys/compat/linux/linux_util.h
+++ sys/compat/linux/linux_util.h
@@ -122,6 +122,7 @@
 int	linux_driver_get_major_minor(const char *node, int *major, int *minor);
 char	*linux_get_char_devices(void);
 void	linux_free_get_char_devices(char *string);
+int	linux_xchroot(struct thread *td);
 
 #if defined(KTR)
 
Index: sys/compat/linux/linux_util.c
===================================================================
--- sys/compat/linux/linux_util.c
+++ sys/compat/linux/linux_util.c
@@ -66,6 +66,49 @@
     linux_emul_path, sizeof(linux_emul_path),
     "Linux runtime environment path");
 
+int
+linux_xchroot(struct thread *td)
+{
+	struct nameidata nd;
+	int error;
+
+	if (!linux_autochroot)
+		return (0);
+
+	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | AUDITVNODE1,
+	    UIO_SYSSPACE, "/compat/ubuntu", td);
+	error = namei(&nd);
+	if (error != 0) {
+		printf("%s: namei returned %d\n", __func__, error);
+		goto error;
+	}
+	error = change_dir(nd.ni_vp, td);
+	if (error != 0) {
+		printf("%s: change_dir returned %d\n", __func__, error);
+		goto e_vunlock;
+	}
+#if 0
+#ifdef MAC
+	error = mac_vnode_check_chroot(td->td_ucred, nd.ni_vp);
+	if (error != 0) {
+		printf("%s: mac_vnode_check_chroot returned %d\n", __func__, error);
+		goto e_vunlock;
+	}
+#endif
+#endif
+	VOP_UNLOCK(nd.ni_vp);
+	error = pwd_xchroot(td, nd.ni_vp);
+	vrele(nd.ni_vp);
+	NDFREE(&nd, NDF_ONLY_PNBUF);
+	return (0);
+e_vunlock:
+	vput(nd.ni_vp);
+error:
+	NDFREE(&nd, NDF_ONLY_PNBUF);
+	return (0);
+}
+
+
 /*
  * Search an alternate path before passing pathname arguments on to
  * system calls. Useful for keeping a separate 'emulation tree'.
@@ -77,7 +120,27 @@
 linux_emul_convpath(struct thread *td, const char *path, enum uio_seg pathseg,
     char **pbuf, int cflag, int dfd)
 {
-	int retval;
+	char *buf;
+	int error, retval;
+
+	if (linux_autochroot) {
+		buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
+
+		/* Append the filename to the prefix. */
+		if (pathseg == UIO_SYSSPACE)
+			error = copystr(path, buf, MAXPATHLEN, NULL);
+		else
+			error = copyinstr(path, buf, MAXPATHLEN, NULL);
+
+		if (error != 0) {
+			free(buf, M_TEMP);
+			*pbuf = NULL;
+		} else {
+			*pbuf = buf;
+		}
+
+		return (error);
+	}
 
 	retval = kern_alternate_path(td, linux_emul_path, path, pathseg, pbuf,
 	    cflag, dfd);
Index: sys/kern/kern_descrip.c
===================================================================
--- sys/kern/kern_descrip.c
+++ sys/kern/kern_descrip.c
@@ -3424,6 +3424,37 @@
 	return (0);
 }
 
+int
+pwd_xchroot(struct thread *td, struct vnode *vp)
+{
+	struct filedesc *fdp;
+	struct pwd *newpwd, *oldpwd;
+
+	fdp = td->td_proc->p_fd;
+	newpwd = pwd_alloc();
+	FILEDESC_XLOCK(fdp);
+	oldpwd = FILEDESC_XLOCKED_LOAD_PWD(fdp);
+	if (oldpwd->pwd_jdir != NULL ||
+	    oldpwd->pwd_rdir != rootvnode) {
+		printf("%s: jailed or chrooted\n", __func__);
+		FILEDESC_XUNLOCK(fdp);
+		pwd_drop(newpwd);
+		return (EBUSY);
+	}
+
+	vrefact(vp);
+	newpwd->pwd_rdir = vp;
+	if (oldpwd->pwd_jdir == NULL) {
+		vrefact(vp);
+		newpwd->pwd_jdir = vp;
+	}
+	pwd_fill(oldpwd, newpwd);
+	pwd_set(fdp, newpwd);
+	FILEDESC_XUNLOCK(fdp);
+	pwd_drop(oldpwd);
+	return (0);
+}
+
 void
 pwd_chdir(struct thread *td, struct vnode *vp)
 {
Index: sys/sys/filedesc.h
===================================================================
--- sys/sys/filedesc.h
+++ sys/sys/filedesc.h
@@ -297,6 +297,7 @@
 /* cdir/rdir/jdir manipulation functions. */
 void	pwd_chdir(struct thread *td, struct vnode *vp);
 int	pwd_chroot(struct thread *td, struct vnode *vp);
+int	pwd_xchroot(struct thread *td, struct vnode *vp);
 void	pwd_ensure_dirs(void);
 void	pwd_set_rootvnode(void);