diff --git a/__init__.py b/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/build.py b/build.py
new file mode 100644
index 0000000..6812e5d
--- /dev/null
+++ b/build.py
@@ -0,0 +1,24 @@
+from .zfs import *
+
+
+def process_step(step, name):
+    cmd=['jail', '-c']
+    cmd.append('path=' + '/focker/' + name)
+
+
+def process_steps(steps, name):
+    if isinstance(steps, list):
+        for step in steps:
+            process_step(step, name)
+    else:
+        process_step(steps, name)
+
+
+def build(spec):
+    if 'base' not in spec:
+        raise ValueError('Missing base specification')
+    base = spec.base
+    base = zfs_snapshot_by_tag_or_name(base)
+
+    root = '/'.join(base.split('/')[:-1])
+    print('base:', base, 'root:', root)
diff --git a/focker-compose.yml b/focker-compose.yml
index 78f5b21..e4be7a5 100644
--- a/focker-compose.yml
+++ b/focker-compose.yml
@@ -1,15 +1,23 @@
+variables:
+  ext_if: em0
+  gateway_ip: 127.0.0.2
+
 defaults:
   jail:
     mount.devfs: true
     interface: lo1
     exec.start: /bin/sh /etc/rc
     exec.stop: /bin/sh /etc/rc.shutdown
+  pf: |
+    rdr on $(ext_if) proto tcp from any to any port 80 -> $(jail_ip)
 
 services:
   gateway:
     image: freebsd-12.1
     jail:
-      ip4.address: 127.0.0.2
+      ip4.address: $(gateway_ip)
+    pf:
+      - pass on $(ext_if)
 
 volumes:
   gateway-data: {}
diff --git a/focker.py b/focker.py
index 77a7911..88f10e5 100644
--- a/focker.py
+++ b/focker.py
@@ -2,6 +2,7 @@ from argparse import ArgumentParser
 import yaml
 import os
 from weir import zfs, process
+from .build import build
 
 
 def clone(self, name, props={}, force=False):
@@ -20,20 +21,7 @@ def clone(self, name, props={}, force=False):
 zfs.ZFSSnapshot.clone = clone
 
 
-def process_step(step, name):
-    cmd=['jail', '-c']
-    cmd.append('path=' + '/focker/' + name)
-
-
-def process_steps(steps, name):
-    if isinstance(steps, list):
-        for step in steps:
-            process_step(step, name)
-    else:
-        process_step(steps, name)
-
-
-def build(args):
+def command_build(args):
     fname = os.path.join(args.focker_dir, 'Fockerfile.yml')
     print('fname:', fname)
     if not os.path.exists(fname):
@@ -41,24 +29,7 @@ def build(args):
     with open(fname, 'r') as f:
         spec = yaml.safe_load(f)
     print('spec:', spec)
-    if 'from' not in spec:
-        raise ValueError('Missing base specification')
-    from_ = zfs.findprops('/', props=['focker:tags'])
-    from_ = filter(lambda a: a['value'] == spec['from'] \
-        and '@' in a['name'], from_)
-    from_ = list(from_)
-    if len(from_) == 0:
-        raise ValueError('Requested base not found')
-    if len(from_) > 1:
-        raise ValueError('Ambiguous base specification')
-    base = from_[0]['name']
-    root = '/'.join(base.split('/')[:-1])
-    print('base:', base)
-    print('root:', root)
-    base = zfs.open(base)
-    name = '/'.join([root, 'x y z'])
-    base.clone(name)
-    process_steps(args['steps'], name)
+    build(spec)
 
 
 def run(args):
@@ -69,7 +40,7 @@ def create_parser():
     parser = ArgumentParser()
     subparsers = parser.add_subparsers()
     parser_build = subparsers.add_parser('build')
-    parser_build.set_defaults(func=build)
+    parser_build.set_defaults(func=command_build)
     parser_build.add_argument('focker_dir', type=str)
     parser_run = subparsers.add_parser('run')
     parser_run.set_defaults(func=run)
@@ -82,4 +53,6 @@ def create_parser():
 
 parser = create_parser()
 args = parser.parse_args()
+if not hasattr(args, 'func'):
+    raise ValueError('You must choose the mode')
 args.func(args)
diff --git a/zfs.py b/zfs.py
index 9660e98..f35576d 100644
--- a/zfs.py
+++ b/zfs.py
@@ -18,3 +18,17 @@ def zfs_parse_output(command):
 def zfs_get_type(name):
     lst = zfs_parse_output(['zfs', 'list', '-o', 'name,type', '-H', name])
     return lst[0][1]
+
+
+def zfs_snapshot_by_tag_or_name(s):
+    lst = zfs_parse_output(['zfs', 'list', '-o', 'name,focker:tags,type', '-H'])
+    lst = list(filter(lambda a: (a[0] == s or s in a[1].split(' ') and a[2] == 'snapshot')))
+    if len(lst) == 0:
+        raise ValueError('Reference not found: ' + s)
+    if len(lst) > 1:
+        raise ValueError('Ambiguous reference: ' + s)
+    return lst[0][0]
+
+
+def zfs_clone(name, target_name):
+    zfs_run(['zfs', 'clone', name, target_name])