diff --git a/commands.py b/commands.py
index 033ec58..d0bae43 100644
--- a/commands.py
+++ b/commands.py
@@ -66,56 +66,74 @@ def all_info(all_cfg):
     return 'currently configured: %s' % ', '.join(info)
 
 
-def frappy_start(service, cfg=None):
-    if service not in SERVICES:
-        raise ValueError('unknown service %s' % service)
-    frappy_config = session.devices.get('frappy_config')
-    # if frappy_config():
-    #    frappy_config.remove_aliases()
-    if cfg == '':
-        seaconn = session.devices.get('seaconn')
-        if seaconn and seaconn._attached_secnode:
-            seaconn.communicate('frappy_remove %s' % service)
-    startnode = None
-    all_cfg = {}
-    for srv in SERVICES:
-        nodename = 'se_' + srv
-        secnode = session.devices.get(nodename)
+def frappy_start(**services):
+    """start/stop  frappy servers
 
-        cfginfo = None if secnode is None else secnode()
-        if srv == service:
-            if cfg is not None:
-                if cfg and not secnode:
-                    AddSetup('frappy_' + service)
-                    secnode = session.devices[nodename]
-                if cfginfo:
-                    secnode('')
-                startnode = secnode
-                cfginfo = cfg
-        elif cfg and cfginfo:
-            # remark: cfg might be a comma separated list of configurations
-            ourcfg = set(cfg.split(','))
-            other = set(cfginfo.split(','))
-            both = other & ourcfg
-            if both:
-                # remove ourcfg from other
-                cfginfo = ','.join(other - ourcfg)
-                # stop other server with the same cfg
-                # or restart with remaining cfgs
-                secnode(cfginfo)
-        all_cfg[srv] = cfginfo
-    if startnode and cfg:
-        startnode(cfg)
-        CreateDevice(str(startnode))
-    if cfg is not None:
+    for example: frappy_start(main='xy', stick='')
+    - restart main server with cfg='xy'
+    - stop stick server
+    - do not touch addons server
+
+    in addition, if a newly given cfg is already used on a running server,
+    this cfg is removed from the server (remark: cfg might be a comma separated list)
+    """
+    frappy_config = session.devices.get('frappy_config')
+    for service in SERVICES:
+        if services.get(service) == '':
+           seaconn = session.devices.get('seaconn')
+           if seaconn and seaconn._attached_secnode:
+               seaconn.communicate('frappy_remove %s' % service)
+    used_cfg = {}
+    # check for duplication of cfgs
+    for service in SERVICES:
+        cfginfo = services.get(service)
+            
+    all_cfg = {}
+    new_cfg = []
+    remove_cfg = []
+    add_setups = []
+    for service in SERVICES:
+        secnode = session.devices.get('se_' + service)
+        cfginfo = services.get(service)
+        if cfginfo is None:
+            if not secnode:
+               continue
+            cfginfo = secnode() or ''
+            all_cfg[service] = cfginfo
+        else:
+            if cfginfo:
+                new_cfg.append((service, secnode, cfginfo))
+                all_cfg[service] = cfginfo
+            else:
+                remove_cfg.append(secnode)
+            if secnode:
+                secnode('')
+        
+        # check cfg is not used twice
+        for cfg in cfginfo.split(','):
+            cfg = cfg.strip()
+            if cfg:
+                prev = used_cfg.get(cfg)
+                if prev:
+                    raise ValueError('%r can not be used in both %s and %s' % (prev, service))
+                used_cfg[cfg] = service
+
+    if new_cfg:
+        for service, secnode, cfginfo in new_cfg:
+            nodename = 'se_' + service
+            if not secnode:
+                AddSetup('frappy_' + service)
+                secnode = session.devices[nodename]
+            secnode(cfginfo)
+            CreateDevice(nodename)
         cleanup_defunct()
         CreateAllDevices()
-        if frappy_config:
-            frappy_config.set_envlist()
-        else:
-            applyAliasConfig()
-        if startnode and cfg == '':
-            startnode.disable()
+    if frappy_config:
+        frappy_config.set_envlist()
+    else:
+        applyAliasConfig()
+    for secnode in remove_cfg:
+        secnode.disable()
     return all_cfg
 
 
@@ -135,9 +153,7 @@ def frappy(main=None, stick=None, addons=None):
     - frappy(''): the stick is removed too
     - addons are not changed when not given!
     """
-    all_cfg = {}
     if main is not None:
-        all_cfg = frappy_start('main', main)
         if stick is None:
             if main:
                 stickcfg = main + 'stick'
@@ -146,10 +162,7 @@ def frappy(main=None, stick=None, addons=None):
                     stick = stickcfg
             else:
                 stick = ''
-    if stick is not None:
-        all_cfg = frappy_stick('stick', stick)
-    if addons is not None:
-        all_cfg = frappy_stick('addons', addons)
+    all_cfg = frappy_start(main=main, stick=stick, addons=addons)
     session.log.info(all_info(all_cfg))
 
 
@@ -161,7 +174,7 @@ def frappy_main(cfg=None):
     - without argument: list running frappy servers
     - cfg = "": stop frappy_main server
     """
-    session.log.info(all_info(frappy_start('main', cfg)))
+    session.log.info(all_info(frappy_start(main=cfg)))
 
 
 @usercommand
@@ -172,7 +185,7 @@ def frappy_stick(cfg=None):
     - without argument: list running frappy servers
     - cfg = "": stop frappy_stick server
     """
-    session.log.info(all_info(frappy_start('stick', cfg)))
+    session.log.info(all_info(frappy_start(stick=cfg)))
 
 
 @usercommand
@@ -183,7 +196,7 @@ def frappy_addons(cfg=None):
     - without argument: list running frappy servers
     - cfg = "": stop frappy_addons server
     """
-    session.log.info(all_info(frappy_start('addons', cfg)))
+    session.log.info(all_info(frappy_start(addons=cfg)))
 
 
 @usercommand