From f88384ec46a059e9601f09133c107a1cc77d3477 Mon Sep 17 00:00:00 2001
From: "atse@norwich.uk.xensource.com" <atse@norwich.uk.xensource.com>
Date: Fri, 22 Sep 2006 11:37:31 +0100
Subject: [PATCH] [XM] Error handling cleanup

Introducing an OptionError exception to be used by all xm subcommands
to signal an error in the arguments. "xm" will catch these and output
the appropriate error and usage message.

Detailed Changes:

main.py:
 *  Cleaned up imports and moved warning filter outside of
    import block.
 *  Converted usage parameters and description to a python
    dict rather than strings to enable better usage help
    formatting.
 *  Removed unused list_label domain command.
 *  Added cmdHelp() prints out usage message for any command
 *  Added shortHelp() prints out the default help message when
    xm is invoked with no arguments.
 *  Added longHelp() prints out long help message when invoked
    with xm --help or xm help.
 *  Added extra optional paramter to getDomains() so we can
    tell Xend not to poll devices. This will speed up xm list.
    (PENDING changes to Xend itself.)
 *  Changed all references where 'dom' actually means 'domid'
    to use the correct name.
 *  Changed 'xm list' header format to use printf formatting style.
 *  Renamed xm_subcommand to xm_importcommand so it is more
    clear what it is doing (all xm commands are subcommands!)
 *  Moved cpu_make_map() inside xm_vcpu_pin as an anonymous func.
 *  Use OptionError whenever an invalid option is detected in xm.
 *  Added proper catch and error printing for XendError and
    OptionErrors in main().

addlabel.py:
cfgbootpolicy.py:
dry-run.py:
dump-policy.py:
get-label.py:
labels.py:
loadpolicy.py:
makepolicy.py:
rmlabel.py:
resources.py:
 *  Replaced usage() with help() that is called from main.py
 *  Replaced usage() invokation with raising OptionError

opts.py:
 *  Added very simple wrap() function that behaves differently
    to textwrap.wrap()
 *  Added OptionError()
 *  Replaced the string representation of Opt, Opts to output
    a nicely formatted usage message.
 *  Changed class Opts itself will throw approriate OptionErrors.
 *  Changed set_bool to recognise 'y' and 'n' as valid input

create.py:
 *  Some whitespace and column width cleanup.
 *  throws OptionError if encounters option error.

migrate.py:
 *  Replace usage() message with the string representation of
    gopts.

sysrq.py:
 * Replace usage message with throwing OptionErrors

Signed-off-by: Alastair Tse <atse@xensource.com>
---
 tools/python/xen/xm/addlabel.py      |  37 +-
 tools/python/xen/xm/cfgbootpolicy.py |  27 +-
 tools/python/xen/xm/console.py       |   2 -
 tools/python/xen/xm/create.py        |  71 ++-
 tools/python/xen/xm/dry-run.py       |  20 +-
 tools/python/xen/xm/dumppolicy.py    |  11 +-
 tools/python/xen/xm/getlabel.py      |  38 +-
 tools/python/xen/xm/labels.py        |  73 ++-
 tools/python/xen/xm/loadpolicy.py    |  19 +-
 tools/python/xen/xm/main.py          | 644 ++++++++++++++++-----------
 tools/python/xen/xm/makepolicy.py    |  10 +-
 tools/python/xen/xm/migrate.py       |  16 +-
 tools/python/xen/xm/opts.py          |  90 +++-
 tools/python/xen/xm/resources.py     |  25 +-
 tools/python/xen/xm/rmlabel.py       |  32 +-
 tools/python/xen/xm/sysrq.py         |  14 +-
 16 files changed, 639 insertions(+), 490 deletions(-)

diff --git a/tools/python/xen/xm/addlabel.py b/tools/python/xen/xm/addlabel.py
index 0a11c35978..7bbe86eecc 100644
--- a/tools/python/xen/xm/addlabel.py
+++ b/tools/python/xen/xm/addlabel.py
@@ -19,19 +19,23 @@
 
 """Labeling a domain configuration file or a resoruce.
 """
-import sys, os
+import os
+import sys
+
 from xen.util import dictio
 from xen.util import security
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm addlabel <label> dom <configfile> [<policy>]"
-    print "       xm addlabel <label> res <resource> [<policy>]\n"
-    print "  This program adds an acm_label entry into the 'configfile'"
-    print "  for a domain or to the global resource label file for a"
-    print "  resource. It derives the policy from the running hypervisor"
-    print "  if it is not given (optional parameter). If a label already"
-    print "  exists for the given domain or resource, then addlabel fails.\n"
-    security.err("Usage")
+def help():
+    return """
+    Format: xm addlabel <label> dom <configfile> [<policy>]
+            xm addlabel <label> res <resource> [<policy>]
+    
+    This program adds an acm_label entry into the 'configfile'
+    for a domain or to the global resource label file for a
+    resource. It derives the policy from the running hypervisor
+    if it is not given (optional parameter). If a label already
+    exists for the given domain or resource, then addlabel fails."""
 
 
 def validate_config_file(configfile):
@@ -114,9 +118,8 @@ def add_domain_label(label, configfile, policyref):
 def main (argv):
     try:
         policyref = None
-        if len(argv) not in [4,5]:
-            usage()
-            return
+        if len(argv) not in (4, 5):
+            raise OptionError('Needs either 2 or 3 arguments')
 
         label = argv[1]
 
@@ -135,20 +138,20 @@ def main (argv):
                     if os.path.isfile(configfile):
                         break
             if not validate_config_file(configfile):
-                usage()
+                raise OptionError('Invalid config file')
             else:
                 add_domain_label(label, configfile, policyref)
         elif argv[2].lower() == "res":
             resource = argv[3]
             add_resource_label(label, resource, policyref)
         else:
-            usage()
-
+            raise OptionError('Need to specify either "dom" or "res" as object to add label to.')
+            
     except security.ACMError:
         sys.exit(-1)
 
-
 if __name__ == '__main__':
     main(sys.argv)
+    
 
 
diff --git a/tools/python/xen/xm/cfgbootpolicy.py b/tools/python/xen/xm/cfgbootpolicy.py
index f62e4c7a8d..d1ed910bf7 100644
--- a/tools/python/xen/xm/cfgbootpolicy.py
+++ b/tools/python/xen/xm/cfgbootpolicy.py
@@ -28,20 +28,17 @@ from xen.util.security import ACMError, err
 from xen.util.security import policy_dir_prefix, boot_filename, xen_title_re
 from xen.util.security import any_title_re, xen_kernel_re, kernel_ver_re, any_module_re
 from xen.util.security import empty_line_re, binary_name_re, policy_name_re
-
-
-def usage():
-    print "\nUsage: xm cfgbootpolicy <policy> [<kernelversion>]\n"
-    print "  Adds a 'module' line to the Xen grub.conf entry"
-    print "  so that xen boots into a specific access control"
-    print "  policy. If kernelversion is not given, then this"
-    print "  script tries to determine it by looking for a grub"
-    print "  entry with a line kernel xen.* If there are multiple"
-    print "  Xen entries, then it must be called with an explicit"
-    print "  version (it will fail otherwise).\n"
-    err("Usage")
-
-
+from xen.xm.opts import OptionError
+
+def help():
+    return """
+    Adds a 'module' line to the Xen grub.conf entry
+    so that xen boots into a specific access control
+    policy. If kernelversion is not given, then this
+    script tries to determine it by looking for a grub
+    entry with a line kernel xen.* If there are multiple
+    Xen entries, then it must be called with an explicit
+    version (it will fail otherwise).\n"""
 
 def determine_kernelversion(user_specified):
     within_xen_title = 0
@@ -152,7 +149,7 @@ def main(argv):
             policy = argv[1]
             user_kver = argv[2]
         else:
-            usage()
+            raise OptionError('Invalid number of arguments')
 
         if not policy_name_re.match(policy):
             err("Illegal policy name \'" + policy + "\'")
diff --git a/tools/python/xen/xm/console.py b/tools/python/xen/xm/console.py
index 95f5a3a0e3..f971644fe9 100644
--- a/tools/python/xen/xm/console.py
+++ b/tools/python/xen/xm/console.py
@@ -18,9 +18,7 @@
 
 XENCONSOLE = "xenconsole"
 
-
 import xen.util.auxbin
 
-
 def execConsole(domid):
     xen.util.auxbin.execute(XENCONSOLE, [str(domid)])
diff --git a/tools/python/xen/xm/create.py b/tools/python/xen/xm/create.py
index 9d5048e445..6194de47a4 100644
--- a/tools/python/xen/xm/create.py
+++ b/tools/python/xen/xm/create.py
@@ -25,7 +25,6 @@ import sys
 import socket
 import re
 import xmlrpclib
-import traceback
 
 from xen.xend import sxp
 from xen.xend import PrettyPrint
@@ -65,35 +64,36 @@ gopts.opt('quiet', short='q',
 
 gopts.opt('path', val='PATH',
           fn=set_value, default='.:/etc/xen',
-          use="""Search path for configuration scripts.
-         The value of PATH is a colon-separated directory list.""")
+          use="Search path for configuration scripts. "
+          "The value of PATH is a colon-separated directory list.")
 
 gopts.opt('defconfig', short='f', val='FILE',
           fn=set_value, default='xmdefconfig',
-          use="""Use the given Python configuration script.
-          The configuration script is loaded after arguments have been processed.
-          Each command-line option sets a configuration variable named after
-          its long option name, and these variables are placed in the
-          environment of the script before it is loaded.
-          Variables for options that may be repeated have list values.
-          Other variables can be set using VAR=VAL on the command line.
-        
-          After the script is loaded, option values that were not set on the
-          command line are replaced by the values set in the script.""")
+          use="Use the given Python configuration script."
+          "The configuration script is loaded after arguments have been "
+          "processed. Each command-line option sets a configuration "
+          "variable named after its long option name, and these "
+          "variables are placed in the environment of the script before "
+          "it is loaded. Variables for options that may be repeated have "
+          "list values. Other variables can be set using VAR=VAL on the "
+          "command line. "     
+          "After the script is loaded, option values that were not set "
+          "on the command line are replaced by the values set in the script.")
 
 gopts.default('defconfig')
 
 gopts.opt('config', short='F', val='FILE',
           fn=set_value, default=None,
-          use="""Domain configuration to use (SXP).
-          SXP is the underlying configuration format used by Xen.
-          SXP configurations can be hand-written or generated from Python configuration
-          scripts, using the -n (dryrun) option to print the configuration.""")
+          use="Domain configuration to use (SXP).\n"
+          "SXP is the underlying configuration format used by Xen.\n"
+          "SXP configurations can be hand-written or generated from Python "
+          "configuration scripts, using the -n (dryrun) option to print\n"
+          "the configuration.")
 
 gopts.opt('dryrun', short='n',
           fn=set_true, default=0,
-          use="""Dry run - print the configuration but don't create the domain.
-          Loads the configuration script, creates the SXP configuration and prints it.""")
+          use="Dry run - prints the resulting configuration in SXP but "
+          "does not create the domain.")
 
 gopts.opt('paused', short='p',
           fn=set_true, default=0,
@@ -105,18 +105,16 @@ gopts.opt('console_autoconnect', short='c',
 
 gopts.var('vncviewer', val='no|yes',
           fn=set_bool, default=None,
-          use="""Spawn a vncviewer listening for a vnc server in the domain.
-          The address of the vncviewer is passed to the domain on the kernel command
-          line using 'VNC_SERVER=<host>:<port>'. The port used by vnc is 5500 + DISPLAY.
-          A display value with a free port is chosen if possible.
-          Only valid when vnc=1.
-          """)
+           use="Spawn a vncviewer listening for a vnc server in the domain.\n"
+           "The address of the vncviewer is passed to the domain on the "
+           "kernel command line using 'VNC_SERVER=<host>:<port>'. The port "
+           "used by vnc is 5500 + DISPLAY. A display value with a free port "
+           "is chosen if possible.\nOnly valid when vnc=1.")
 
 gopts.var('vncconsole', val='no|yes',
           fn=set_bool, default=None,
-          use="""Spawn a vncviewer process for the domain's graphical console.
-          Only valid when vnc=1.
-          """)
+          use="Spawn a vncviewer process for the domain's graphical console.\n"
+          "Only valid when vnc=1.")
 
 gopts.var('name', val='NAME',
           fn=set_value, default=None,
@@ -440,7 +438,6 @@ gopts.var('uuid', val='',
           addresses for virtual network interfaces.  This must be a unique 
           value across the entire cluster.""")
 
-
 def err(msg):
     """Print an error to stderr and exit.
     """
@@ -490,7 +487,6 @@ def configure_disks(config_devs, vals):
     """Create the config for disks (virtual block devices).
     """
     for (uname, dev, mode, backend) in vals.disk:
-
         if uname.startswith('tap:'):
             cls = 'tap'
         else:
@@ -851,7 +847,6 @@ def choose_vnc_display():
         if port in ports: continue
         return d
     return None
-
 vncpid = None
 
 def daemonize(prog, args):
@@ -885,7 +880,6 @@ def daemonize(prog, args):
             w.write(str(pid2 or 0))
             w.close()
             os._exit(0)
-
     os.close(w)
     r = os.fdopen(r)
     daemon_pid = int(r.read())
@@ -904,6 +898,7 @@ def spawn_vnc(display):
     vncpid = daemonize("vncviewer", vncargs)
     if vncpid == 0:
         return 0
+
     return VNC_BASE_PORT + display
 
 def preprocess_vnc(vals):
@@ -1091,7 +1086,6 @@ def check_domain_label(config, verbose):
 
     return answer
 
-
 def config_security_check(config, verbose):
     """Checks each resource listed in the config to see if the active
        policy will permit creation of a new domain using the config.
@@ -1145,7 +1139,6 @@ def config_security_check(config, verbose):
 
     return answer
 
-
 def create_security_check(config):
     passed = 0
     try:
@@ -1158,7 +1151,9 @@ def create_security_check(config):
         sys.exit(-1)
 
     return passed
-
+  
+def help():
+    return str(gopts)
 
 def main(argv):
     try:
@@ -1176,11 +1171,11 @@ def main(argv):
         PrettyPrint.prettyprint(config)
     else:
         if not create_security_check(config):
-            err("Security configuration prevents domain from starting.")
+            raise OptionError('Security Configuration prevents domain from starting')
         else:
             dom = make_domain(opts, config)
             if opts.vals.console_autoconnect:
-                console.execConsole(dom)
-        
+                console.execConsole(dom)        
+             
 if __name__ == '__main__':
     main(sys.argv)
diff --git a/tools/python/xen/xm/dry-run.py b/tools/python/xen/xm/dry-run.py
index 924235c392..72edcd6cb5 100644
--- a/tools/python/xen/xm/dry-run.py
+++ b/tools/python/xen/xm/dry-run.py
@@ -22,20 +22,18 @@ import sys
 from xen.util import security
 from xen.xm import create
 from xen.xend import sxp
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm dry-run <configfile>\n"
-    print "This program checks each resource listed in the configfile"
-    print "to see if the domain created by the configfile can access"
-    print "the resources.  The status of each resource is listed"
-    print "individually along with the final security decision.\n"
-    security.err("Usage")
-
+def help():
+    return """
+    This program checks each resource listed in the configfile
+    to see if the domain created by the configfile can access
+    the resources.  The status of each resource is listed
+    individually along with the final security decision."""
 
 def main (argv):
-    try:
-        if len(argv) != 2:
-            usage()
+    if len(argv) != 2:
+        raise OptionError('Invalid number of arguments')
 
         passed = 0
         (opts, config) = create.parseCommandLine(argv)
diff --git a/tools/python/xen/xm/dumppolicy.py b/tools/python/xen/xm/dumppolicy.py
index 9df36611be..3de9e42a19 100644
--- a/tools/python/xen/xm/dumppolicy.py
+++ b/tools/python/xen/xm/dumppolicy.py
@@ -21,12 +21,10 @@ import sys
 from xen.util.security import ACMError, err, dump_policy
 
 
-def usage():
-    print "\nUsage: xm dumppolicy\n"
-    print " Retrieve and print currently enforced"
-    print " hypervisor policy information (low-level).\n"
-    err("Usage")
-
+def help():
+    return """
+    Retrieve and print currently enforced hypervisor policy information
+    (low-level)."""
 
 def main(argv):
     try:
@@ -34,7 +32,6 @@ def main(argv):
             usage()
 
         dump_policy()
-
     except ACMError:
         sys.exit(-1)
 
diff --git a/tools/python/xen/xm/getlabel.py b/tools/python/xen/xm/getlabel.py
index 3450d2799c..28e4619f45 100644
--- a/tools/python/xen/xm/getlabel.py
+++ b/tools/python/xen/xm/getlabel.py
@@ -21,13 +21,13 @@
 import sys, os, re
 from xen.util import dictio
 from xen.util import security
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm getlabel dom <configfile>"
-    print "       xm getlabel res <resource>\n"
-    print "  This program shows the label for a domain or resource.\n"
-    security.err("Usage")
-
+def help():
+    return """
+    Usage: xm getlabel dom <configfile>"
+           xm getlabel res <resource>\n"
+    This program shows the label for a domain or resource."""
 
 def get_resource_label(resource):
     """Gets the resource label
@@ -90,21 +90,17 @@ def get_domain_label(configfile):
 
 
 def main (argv):
-    try:
-        if len(argv) != 3:
-            usage()
-
-        if argv[1].lower() == "dom":
-            configfile = argv[2]
-            get_domain_label(configfile)
-        elif argv[1].lower() == "res":
-            resource = argv[2]
-            get_resource_label(resource)
-        else:
-            usage()
-
-    except security.ACMError:
-        sys.exit(-1)
+    if len(argv) != 3:
+        raise OptionError('Requires 2 arguments')
+
+    if argv[1].lower() == "dom":
+        configfile = argv[2]
+        get_domain_label(configfile)
+    elif argv[1].lower() == "res":
+        resource = argv[2]
+        get_resource_label(resource)
+    else:
+        raise OptionError('First subcommand argument must be "dom" or "res"')
 
 if __name__ == '__main__':
     main(sys.argv)
diff --git a/tools/python/xen/xm/labels.py b/tools/python/xen/xm/labels.py
index 6536b5e27d..d84b211800 100644
--- a/tools/python/xen/xm/labels.py
+++ b/tools/python/xen/xm/labels.py
@@ -23,49 +23,46 @@ import traceback
 import string
 from xen.util.security import ACMError, err, list_labels, active_policy
 from xen.util.security import vm_label_re, res_label_re, all_label_re
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm labels [<policy>] [<type=dom|res|any>]\n"
-    print " Prints labels of the specified type (default is dom)"
-    print " that are defined in policy (default is current"
-    print " hypervisor policy).\n"
-    err("Usage")
 
+def help():
+    return """
+    Prints labels of the specified type (default is dom)
+    that are defined in policy (default is current hypervisor policy)."""
 
 def main(argv):
-    try:
-        policy = None
-        type = None
-        for i in argv[1:]:
-            i_s = string.split(i, '=')
-            if len(i_s) > 1:
-                if (i_s[0] == 'type') and (len(i_s) == 2):
-                    if not type:
-                        type = i_s[1]
-                    else:
-                        usage()
-                else:
-                    usage()
-            else:
-                if not policy:
-                    policy = i
-                else:
-                    usage()
-
-        if not policy:
-            policy = active_policy
-            if active_policy in ['NULL', 'INACTIVE', 'DEFAULT']:
-                err("No policy active. Please specify the <policy> parameter.")
+    policy = None
+    ptype = None
+    for arg in argv[1:]:
+        key_val = arg.split('=')
+        if len(key_val) == 2 and key_val[0] == 'type':
+            if ptype:
+                raise OptionError('type is definied twice')
+            ptype = key_val[1].lower()
 
-        if not type or (type in ['DOM', 'dom']):
-            condition = vm_label_re
-        elif type in ['RES', 'res']:
-            condition = res_label_re
-        elif type in ['ANY', 'any']:
-            condition = all_label_re
+        elif len(key_val) == 1:
+            if policy:
+                raise OptionError('policy is defined twice')
+            policy = arg
         else:
-            err("Unknown label type \'" + type + "\'")
+            raise OptionError('Unrecognised option: %s' % arg)
+
+    if not policy:
+        policy = active_policy
+        if active_policy in ['NULL', 'INACTIVE', 'DEFAULT']:
+            raise OptionError('No policy active, you must specify a <policy>')
+
+    if not ptype or ptype == 'dom':
+        condition = vm_label_re
+    elif ptype == 'res':
+        condition = res_label_re
+    elif ptype == 'any':
+        condition = all_label_re
+    else:
+        err("Unknown label type \'" + ptype + "\'")
 
+    try:
         labels = list_labels(policy, condition)
         labels.sort()
         for label in labels:
@@ -74,9 +71,7 @@ def main(argv):
     except ACMError:
         sys.exit(-1)
     except:
-        traceback.print_exc(limit=1)
-        sys.exit(-1)
-
+        traceback.print_exc(limit = 1)
 
 if __name__ == '__main__':
     main(sys.argv)
diff --git a/tools/python/xen/xm/loadpolicy.py b/tools/python/xen/xm/loadpolicy.py
index 3eb0e28e75..947da2e7fa 100644
--- a/tools/python/xen/xm/loadpolicy.py
+++ b/tools/python/xen/xm/loadpolicy.py
@@ -21,26 +21,23 @@
 import sys
 import traceback
 from xen.util.security import ACMError, err, load_policy
+from xen.xm.opts import OptionError
 
-
-def usage():
-    print "\nUsage: xm loadpolicy <policy>\n"
-    print " Load the compiled binary (.bin) policy"
-    print " into the running hypervisor.\n"
-    err("Usage")
+def help():
+    return """Load the compiled binary (.bin) policy into the running
+    hypervisor."""
 
 def main(argv):
+    if len(argv) != 2:
+        raise OptionError('No policy defined')
+    
     try:
-        if len(argv) != 2:
-            usage()
         load_policy(argv[1])
 
     except ACMError:
         sys.exit(-1)
     except:
-        traceback.print_exc(limit=1)
-        sys.exit(-1)
-
+        traceback.print_exc(limit = 1)
 
 if __name__ == '__main__':
     main(sys.argv)
diff --git a/tools/python/xen/xm/main.py b/tools/python/xen/xm/main.py
index 0beb00e6e2..2bf6f80aeb 100644
--- a/tools/python/xen/xm/main.py
+++ b/tools/python/xen/xm/main.py
@@ -22,28 +22,27 @@
 """Grand unified management application for Xen.
 """
 import os
-import os.path
 import sys
 import re
 import getopt
 import socket
-import warnings
-warnings.filterwarnings('ignore', category=FutureWarning)
+import traceback
 import xmlrpclib
 import traceback
 import datetime
+from select import select
 
-import xen.xend.XendProtocol
+import warnings
+warnings.filterwarnings('ignore', category=FutureWarning)
 
 from xen.xend import PrettyPrint
 from xen.xend import sxp
-from xen.xm.opts import *
-
-import console
-import xen.xend.XendClient
+from xen.xend import XendClient
 from xen.xend.XendClient import server
+
+from xen.xm.opts import OptionError, Opts, wrap, set_true
+from xen.xm import console
 from xen.util import security
-from select import select
 
 # getopt.gnu_getopt is better, but only exists in Python 2.3+.  Use
 # getopt.getopt if gnu_getopt is not available.  This will mean that options
@@ -51,93 +50,148 @@ from select import select
 if not hasattr(getopt, 'gnu_getopt'):
     getopt.gnu_getopt = getopt.getopt
 
+# General help message
+
+USAGE_HELP = "Usage: xm <subcommand> [args]\n\n" \
+             "Control, list, and manipulate Xen guest instances.\n"
+
+USAGE_FOOTER = '<Domain> can either be the Domain Name or Id.\n' \
+               'For more help on \'xm\' see the xm(1) man page.\n' \
+               'For more help on \'xm create\' see the xmdomain.cfg(5) '\
+               ' man page.\n'
 
-# Strings for shorthelp
-console_help = "console <DomId>                  Attach to domain DomId's console."
-create_help =  """create [-c] <ConfigFile>
-               [Name=Value]..       Create a domain based on Config File"""
-destroy_help = "destroy <DomId>                  Terminate a domain immediately"
-dump_core_help =   """dump-core [-L|--live][-C|--crash]
-            <DomId> [FileName]      Dump core of the specified domain"""
-
-help_help =    "help                             Display this message"
-list_help =    "list [--long] [DomId, ...]       List information about domains"
-list_label_help = "list [--label] [DomId, ...]      List information about domains including their labels"
-
-mem_max_help = "mem-max <DomId> <Mem>            Set maximum memory reservation for a domain"
-mem_set_help = "mem-set <DomId> <Mem>            Adjust the current memory usage for a domain"
-migrate_help = "migrate <DomId> <Host>           Migrate a domain to another machine"
-pause_help =   "pause <DomId>                    Pause execution of a domain"
-reboot_help =  "reboot <DomId> [-w][-a]          Reboot a domain"
-restore_help = "restore <File>                   Create a domain from a saved state file"
-save_help =    "save <DomId> <File>              Save domain state (and config) to file"
-shutdown_help ="shutdown <DomId> [-w][-a][-R|-H] Shutdown a domain"
-top_help =     "top                              Monitor system and domains in real-time"
-unpause_help = "unpause <DomId>                  Unpause a paused domain"
-uptime_help  = "uptime [-s|--short] [DomId, ...] List uptime for domains"
-
-help_spacer = """
-   """
-
-# Strings for longhelp
-sysrq_help =   "sysrq   <DomId> <letter>         Send a sysrq to a domain"
-domid_help =   "domid <DomName>                  Converts a domain name to a domain id"
-domname_help = "domname <DomId>                  Convert a domain id to a domain name"
-vcpu_set_help = """vcpu-set <DomId> <VCPUs>         Set the number of active VCPUs for a domain
-                                    within the range allowed by the domain
-                                    configuration"""
-vcpu_list_help = "vcpu-list <DomId>                List the VCPUs for a domain (or all domains)"
-vcpu_pin_help = "vcpu-pin <DomId> <VCPU> <CPUs>   Set which cpus a VCPU can use" 
-dmesg_help =   "dmesg [-c|--clear]               Read or clear Xen's message buffer"
-info_help =    "info                             Get information about the xen host"
-rename_help =  "rename <DomId> <New Name>        Rename a domain"
-log_help =     "log                              Print the xend log"
-sched_sedf_help = "sched-sedf [DOM] [OPTIONS]       Show|Set simple EDF parameters\n" + \
-"              -p, --period          Relative deadline(ms).\n\
-              -s, --slice           Worst-case execution time(ms)\n\
-                                    (slice < period).\n\
-              -l, --latency         scaled period(ms) in case the domain\n\
-                                    is doing heavy I/O.\n\
-              -e, --extra           flag (0/1) which controls whether the\n\
-                                    domain can run in extra-time\n\
-              -w, --weight          mutually exclusive with period/slice and\n\
-                                    specifies another way of setting a domain's\n\
-                                    cpu period/slice."
-
-sched_credit_help = "sched-credit                           Set or get credit scheduler parameters"
-block_attach_help = """block-attach <DomId> <BackDev> <FrontDev> <Mode>
-                [BackDomId]         Create a new virtual block device"""
-block_detach_help = """block-detach  <DomId> <DevId>    Destroy a domain's virtual block device,
-                                    where <DevId> may either be the device ID
-                                    or the device name as mounted in the guest"""
-
-block_list_help = "block-list <DomId> [--long]      List virtual block devices for a domain"
-block_configure_help = """block-configure <DomId> <BackDev> <FrontDev> <Mode>
-                   [BackDomId] Change block device configuration"""
-network_attach_help = """network-attach  <DomID> [script=<script>] [ip=<ip>] [mac=<mac>]
-                           [bridge=<bridge>] [backend=<backDomID>]
-                                    Create a new virtual network device """
-network_detach_help = """network-detach  <DomId> <DevId>  Destroy a domain's virtual network
-                                    device, where <DevId> is the device ID."""
-
-network_list_help = "network-list <DomId> [--long]    List virtual network interfaces for a domain"
-vnet_list_help = "vnet-list [-l|--long]            list vnets"
-vnet_create_help = "vnet-create <config>             create a vnet from a config file"
-vnet_delete_help = "vnet-delete <vnetid>             delete a vnet"
-vtpm_list_help = "vtpm-list <DomId> [--long]       list virtual TPM devices"
-addlabel_help =  "addlabel <label> dom <configfile> Add security label to domain\n            <label> res <resource>   or resource"
-rmlabel_help =  "rmlabel dom <configfile>         Remove security label from domain\n           res <resource>           or resource"
-getlabel_help =  "getlabel dom <configfile>        Show security label for domain\n            res <resource>          or resource"
-dry_run_help =  "dry-run <configfile>             Tests if domain can access its resources"
-resources_help =  "resources                        Show info for each labeled resource"
-cfgbootpolicy_help = "cfgbootpolicy <policy>           Add policy to boot configuration "
-dumppolicy_help = "dumppolicy                       Print hypervisor ACM state information"
-loadpolicy_help = "loadpolicy <policy>              Load binary policy into hypervisor"
-makepolicy_help = "makepolicy <policy>              Build policy and create .bin/.map files"
-labels_help     = "labels [policy] [type=DOM|..]    List <type> labels for (active) policy."
-serve_help      = "serve                            Proxy Xend XML-RPC over stdio"
-
-short_command_list = [
+# Help strings are indexed by subcommand name in this way:
+# 'subcommand': (argstring, description)
+
+SUBCOMMAND_HELP = {
+    # common commands
+    
+    'console'     : ('<Domain>',
+                     'Attach to <Domain>\'s console.'),
+    'create'      : ('<ConfigFile> [options] [vars]',
+                     'Create a domain based on <ConfigFile>.'),
+    'destroy'     : ('<Domain>',
+                     'Terminate a domain immediately.'),
+    'help'        : ('', 'Display this message.'),
+    'list'        : ('[options] [Domain, ...]',
+                     'List information about all/some domains.'),
+    'mem-max'     : ('<Domain> <Mem>',
+                     'Set the maximum amount reservation for a domain.'),
+    'mem-set'     : ('<Domain> <Mem>',
+                     'Set the current memory usage for a domain.'),
+    'migrate'     : ('<Domain> <Host>',
+                     'Migrate a domain to another machine.'),
+    'pause'       : ('<Domain>', 'Pause execution of a domain.'),
+    'reboot'      : ('<Domain> [-wa]', 'Reboot a domain.'),
+    'restore'     : ('<CheckpointFile>',
+                     'Restore a domain from a saved state.'),
+    'save'        : ('<Domain> <CheckpointFile>',
+                     'Save a domain state to restore later.'),
+    'shutdown'    : ('<Domain> [-waRH]', 'Shutdown a domain.'),
+    'top'         : ('', 'Monitor a host and the domains in real time.'),
+    'unpause'     : ('<Domain>', 'Unpause a paused domain.'),
+    'uptime'      : ('[-s] <Domain>', 'Print uptime for a domain.'),
+
+    # less used commands
+
+    'dmesg'       : ('[-c|--clear]',
+                     'Read and/or clear Xend\'s message buffer.'),
+    'domid'       : ('<DomainName>', 'Convert a domain name to domain id.'),
+    'domname'     : ('<DomId>', 'Convert a domain id to domain name.'),
+    'dump-core'   : ('[-L|--live] [-C|--crash] <Domain> [Filename]',
+                     'Dump core for a specific domain.'),
+    'info'        : ('', 'Get information about Xen host.'),
+    'log'         : ('', 'Print Xend log'),
+    'rename'      : ('<Domain> <NewDomainName>', 'Rename a domain.'),
+    'sched-sedf'  : ('<Domain> [options]', 'Get/set EDF parameters.'),
+    'sched-credit': ('-d <Domain> [-w[=WEIGHT]|-c[=CAP]]',
+                     'Get/set credit scheduler parameters.'),
+    'sysrq'       : ('<Domain> <letter>', 'Send a sysrq to a domain.'),
+    'vcpu-list'   : ('[<Domain>]',
+                     'List the VCPUs for a domain or all domains.'),
+    'vcpu-pin'    : ('<Domain> <VCPU> <CPUs>',
+                     'Set which CPUs a VCPU can use.'),
+    'vcpu-set'    : ('<Domain> <vCPUs>',
+                     'Set the number of active VCPUs for allowed for the'
+                     ' domain.'),
+
+    # device commands
+
+    'block-attach'  :  ('<Domain> <BackDev> <FrontDev> <Mode>',
+                        'Create a new virtual block device.'),
+    'block-configure': ('<Domain> <BackDev> <FrontDev> <Mode> [BackDomId]',
+                        'Change block device configuration'),
+    'block-detach'  :  ('<Domain> <DevId>',
+                        'Destroy a domain\'s virtual block device.'),
+    'block-list'    :  ('<Domain> [--long]',
+                        'List virtual block devices for a domain.'),
+    'network-attach':  ('<Domain> [--script=<script>] [--ip=<ip>] '
+                        '[--mac=<mac>]',
+                        'Create a new virtual network device.'),
+    'network-detach':  ('<Domain> <DevId>',
+                        'Destroy a domain\'s virtual network device.'),
+    'network-list'  :  ('<Domain> [--long]',
+                        'List virtual network interfaces for a domain.'),
+    'vnet-create'   :  ('<ConfigFile>','Create a vnet from ConfigFile.'),
+    'vnet-delete'   :  ('<VnetId>', 'Delete a Vnet.'),
+    'vnet-list'     :  ('[-l|--long]', 'List Vnets.'),
+    'vtpm-list'     :  ('<Domain> [--long]', 'List virtual TPM devices.'),
+
+    # security
+
+    'addlabel'      :  ('<label> {dom <ConfigFile>|res <resource>} [<policy>]',
+                        'Add security label to domain.'),
+    'rmlabel'       :  ('{dom <ConfigFile>|res <Resource>}',
+                        'Remove a security label from domain.'),
+    'getlabel'      :  ('{dom <ConfigFile>|res <Resource>}',
+                        'Show security label for domain or resource.'),
+    'dry-run'       :  ('<ConfigFile>',
+                        'Test if a domain can access its resources.'),
+    'resources'     :  ('', 'Show info for each labeled resource.'),
+    'cfgbootpolicy' :  ('<policy> [kernelversion]',
+                        'Add policy to boot configuration.'),
+    'dumppolicy'    :  ('', 'Print hypervisor ACM state information.'),
+    'loadpolicy'    :  ('<policy.bin>', 'Load binary policy into hypervisor.'),
+    'makepolicy'    :  ('<policy>', 'Build policy and create .bin/.map '
+                        'files.'),
+    'labels'        :  ('[policy] [type=dom|res|any]',
+                        'List <type> labels for (active) policy.'),
+    'serve'         :  ('', 'Proxy Xend XMLRPC over stdio.'),
+}
+
+SUBCOMMAND_OPTIONS = {
+    'sched-sedf': (
+       ('-p [MS]', '--period[=MS]', 'Relative deadline(ms)'),
+       ('-s [MS]', '--slice[=MS]' ,
+        'Worst-case execution time(ms). (slice < period)'),
+       ('-l [MS]', '--latency[=MS]',
+        'Scaled period (ms) when domain performs heavy I/O'),
+       ('-e [FLAG]', '--extra[=FLAG]',
+        'Flag (0 or 1) controls if domain can run in extra time.'),
+       ('-w [FLOAT]', '--weight[=FLOAT]',
+        'CPU Period/slice (do not set with --period/--slice)'),
+    ),
+    'sched-credit': (
+       ('-d DOMAIN', '--domain=DOMAIN', 'Domain to modify'),
+       ('-w WEIGHT', '--weight=WEIGHT', 'Weight (int)'),
+       ('-c CAP',    '--cap=CAP',       'Cap (int)'),
+    ),
+    'list': (
+       ('-l', '--long', 'Output all VM details in SXP'),
+       ('', '--label',  'Include security labels'),
+    ),
+    'dmesg': (
+       ('-c', '--clear', 'Clear dmesg buffer'),
+    ),
+    'vnet-list': (
+       ('-l', '--long', 'List Vnets as SXP'),
+    ),
+    'network-list': (
+       ('-l', '--long', 'List resources as SXP'),
+    ),
+}
+
+common_commands = [
     "console",
     "create",
     "destroy",
@@ -165,7 +219,6 @@ domain_commands = [
     "domname",
     "dump-core",
     "list",
-    "list_label",
     "mem-max",
     "mem-set",
     "migrate",
@@ -223,67 +276,105 @@ acm_commands = [
     "makepolicy",
     "loadpolicy",
     "cfgbootpolicy",
-    "dumppolicy"
+    "dumppolicy",
     ]
 
 all_commands = (domain_commands + host_commands + scheduler_commands +
                 device_commands + vnet_commands + acm_commands)
 
+####################################################################
+#
+#  Help/usage printing functions
+#
+####################################################################
 
-def commandToHelp(cmd):
-    return eval(cmd.replace("-", "_") + "_help")
-
-
-shorthelp = """Usage: xm <subcommand> [args]
-    Control, list, and manipulate Xen guest instances
-
-xm common subcommands:
-   """  + help_spacer.join(map(commandToHelp, short_command_list))  + """
-
-<DomName> can be substituted for <DomId> in xm subcommands.
-
-For a complete list of subcommands run 'xm help --long'
-For more help on xm see the xm(1) man page
-For more help on xm create, see the xmdomain.cfg(5) man page"""
-
-longhelp = """Usage: xm <subcommand> [args]
-    Control, list, and manipulate Xen guest instances
-
-xm full list of subcommands:
-
-  Domain Commands:
-   """ + help_spacer.join(map(commandToHelp,  domain_commands)) + """
-
-  Xen Host Commands:
-   """ + help_spacer.join(map(commandToHelp,  host_commands)) + """
-
-  Scheduler Commands:
-   """ + help_spacer.join(map(commandToHelp,  scheduler_commands)) + """
-
-  Virtual Device Commands:
-   """  + help_spacer.join(map(commandToHelp, device_commands)) + """
-
-  Vnet commands:
-   """ + help_spacer.join(map(commandToHelp,  vnet_commands)) + """
-
-  Access Control commands:
-   """ + help_spacer.join(map(commandToHelp,  acm_commands)) + """
-
-<DomName> can be substituted for <DomId> in xm subcommands.
+def cmdHelp(cmd):
+    """Print help for a specific subcommand."""
+    
+    try:
+        args, desc = SUBCOMMAND_HELP[cmd]
+    except KeyError:
+        shortHelp()
+        return
+    
+    print 'Usage: xm %s %s' % (cmd, args)
+    print
+    print desc
+    
+    try:
+        # If options help message is defined, print this.
+        for shortopt, longopt, desc in SUBCOMMAND_OPTIONS[cmd]:
+            if shortopt and longopt:
+                optdesc = '%s, %s' % (shortopt, longopt)
+            elif shortopt:
+                optdesc = shortopt
+            elif longopt:
+                optdesc = longopt
+
+            wrapped_desc = wrap(desc, 43)   
+            print '  %-30s %-43s' % (optdesc, wrapped_desc[0])
+            for line in wrapped_desc[1:]:
+                print ' ' * 33 + line
+        print
+    except KeyError:
+        # if the command is an external module, we grab usage help
+        # from the module itself.
+        if cmd in IMPORTED_COMMANDS:
+            try:
+                cmd_module =  __import__(cmd, globals(), locals(), 'xen.xm')
+                cmd_usage = getattr(cmd_module, "help", None)
+                if cmd_usage:
+                    print cmd_usage()
+            except ImportError:
+                pass
+        
+def shortHelp():
+    """Print out generic help when xm is called without subcommand."""
+    
+    print USAGE_HELP
+    print 'Common \'xm\' commands:\n'
+    
+    for command in common_commands:
+        try:
+            args, desc = SUBCOMMAND_HELP[command]
+        except KeyError:
+            continue
+        wrapped_desc = wrap(desc, 50)
+        print ' %-20s %-50s' % (command, wrapped_desc[0])
+        for line in wrapped_desc[1:]:
+            print ' ' * 22 + line
+
+    print
+    print USAGE_FOOTER
+    print 'For a complete list of subcommands run \'xm help\'.'
+    
+def longHelp():
+    """Print out full help when xm is called with xm --help or xm help"""
+    
+    print USAGE_HELP
+    print 'xm full list of subcommands:\n'
+    
+    for command in all_commands:
+        try:
+            args, desc = SUBCOMMAND_HELP[command]
+        except KeyError:
+            continue
 
-For a short list of subcommands run 'xm help'
-For more help on xm see the xm(1) man page
-For more help on xm create, see the xmdomain.cfg(5) man page"""
+        wrapped_desc = wrap(desc, 50)
+        print ' %-20s %-50s' % (command, wrapped_desc[0])
+        for line in wrapped_desc[1:]:
+            print ' ' * 22 + line        
 
-# array for xm help <command>
-help = {
-    "--long": longhelp
-    }
+    print
+    print USAGE_FOOTER        
 
-for command in all_commands:
-    # create is handled specially
-    if (command != 'create'):
-        help[command] = commandToHelp(command)
+def usage(cmd = None):
+    """ Print help usage information and exits """
+    if cmd:
+        cmdHelp(cmd)
+    else:
+        shortHelp()
+    sys.exit(1)
 
 
 ####################################################################
@@ -298,7 +389,7 @@ def arg_check(args, name, lo, hi = -1):
     if hi == -1:
         if n != lo:
             err("'xm %s' requires %d argument%s.\n" % (name, lo,
-                                                       lo > 1 and 's' or ''))
+                                                       lo == 1 and '' or 's'))
             usage(name)
     else:
         if n < lo or n > hi:
@@ -345,14 +436,19 @@ def err(msg):
 def xm_save(args):
     arg_check(args, "save", 2)
 
-    dom = args[0] # TODO: should check if this exists
+    try:
+        dominfo = parse_doms_info(server.xend.domain(args[0]))
+    except xmlrpclib.Fault, ex:
+        raise ex
+    
+    domid = dominfo['domid']
     savefile = os.path.abspath(args[1])
 
     if not os.access(os.path.dirname(savefile), os.W_OK):
         err("xm save: Unable to create file %s" % savefile)
         sys.exit(1)
     
-    server.xend.domain.save(dom, savefile)
+    server.xend.domain.save(domid, savefile)
     
 def xm_restore(args):
     arg_check(args, "restore", 1)
@@ -366,9 +462,9 @@ def xm_restore(args):
     server.xend.domain.restore(savefile)
 
 
-def getDomains(domain_names):
+def getDomains(domain_names, full = 0):
     if domain_names:
-        return map(server.xend.domain, domain_names)
+        return [server.xend.domain(dom) for dom in domain_names]
     else:
         return server.xend.domains(1)
 
@@ -378,9 +474,11 @@ def xm_list(args):
     show_vcpus = 0
     show_labels = 0
     try:
-        (options, params) = getopt.gnu_getopt(args, 'lv', ['long','vcpus','label'])
+        (options, params) = getopt.gnu_getopt(args, 'lv',
+                                              ['long','vcpus','label'])
     except getopt.GetoptError, opterr:
         err(opterr)
+        usage('list')
         sys.exit(1)
     
     for (k, v) in options:
@@ -397,7 +495,7 @@ def xm_list(args):
         xm_vcpu_list(params)
         return
 
-    doms = getDomains(params)
+    doms = getDomains(params, use_long)
 
     if use_long:
         map(PrettyPrint.prettyprint, doms)
@@ -412,7 +510,7 @@ def parse_doms_info(info):
         return t(sxp.child_value(info, n, d))
     
     return {
-        'dom'      : get_info('domid',        int,   -1),
+        'domid'    : get_info('domid',        int,   -1),
         'name'     : get_info('name',         str,   '??'),
         'mem'      : get_info('memory',       int,   0),
         'vcpus'    : get_info('online_vcpus', int,   0),
@@ -428,7 +526,7 @@ def parse_sedf_info(info):
         return t(sxp.child_value(info, n, d))
 
     return {
-        'dom'      : get_info('domain',        int,   -1),
+        'domid'    : get_info('domid',         int,   -1),
         'period'   : get_info('period',        int,   -1),
         'slice'    : get_info('slice',         int,   -1),
         'latency'  : get_info('latency',       int,   -1),
@@ -436,34 +534,40 @@ def parse_sedf_info(info):
         'weight'   : get_info('weight',        int,   -1),
         }
 
-
 def xm_brief_list(doms):
-    print 'Name                              ID Mem(MiB) VCPUs State  Time(s)'
+    print '%-40s %3s %8s %5s %5s %9s' % \
+          ('Name', 'ID', 'Mem(MiB)', 'VCPUs', 'State', 'Time(s)')
+    
+    format = "%(name)-40s %(domid)3d %(mem)8d %(vcpus)5d %(state)5s " \
+             "%(cpu_time)8.1f"
+    
     for dom in doms:
         d = parse_doms_info(dom)
-        print ("%(name)-32s %(dom)3d %(mem)8d %(vcpus)5d %(state)5s %(cpu_time)7.1f" % d)
-
+        print format % d
 
 def xm_label_list(doms):
+    print '%-32s %3s %8s %5s %5s %9s %-8s' % \
+          ('Name', 'ID', 'Mem(MiB)', 'VCPUs', 'State', 'Time(s)', 'Label')
+    
     output = []
-    print 'Name                              ID Mem(MiB) VCPUs State  Time(s)  Label'
+    format = '%(name)-32s %(domid)3d %(mem)8d %(vcpus)5d %(state)5s ' \
+             '%(cpu_time)8.1f %(seclabel)9s'
+    
     for dom in doms:
         d = parse_doms_info(dom)
-        l = "%(name)-32s %(dom)3d %(mem)8d %(vcpus)5d %(state)5s %(cpu_time)7.1f  " % d
         if security.active_policy not in ['INACTIVE', 'NULL', 'DEFAULT']:
-            if d['seclabel']:
-                line = (l, d['seclabel'])
-            else:
-                line = (l, "ERROR")
+            if not d['seclabel']:
+                d['seclabel'] = 'ERROR'
         elif security.active_policy in ['DEFAULT']:
-            line = (l, "DEFAULT")
+            d['seclabel'] = 'DEFAULT'
         else:
-            line = (l, "INACTIVE")
-        output.append(line)
+            d['seclabel'] = 'INACTIVE'
+        output.append((format % d, d['seclabel']))
+        
     #sort by labels
     output.sort(lambda x,y: cmp( x[1].lower(), y[1].lower()))
-    for l in output:
-        print l[0] + l[1]
+    for line, label in output:
+        print line
 
 
 def xm_vcpu_list(args):
@@ -474,7 +578,11 @@ def xm_vcpu_list(args):
         doms = server.xend.domains(False)
         dominfo = map(server.xend.domain.getVCPUInfo, doms)
 
-    print 'Name                              ID  VCPU  CPU  State  Time(s)  CPU Affinity'
+    print '%-32s %3s %5s %5s %5s %9s %s' % \
+          ('Name', 'ID', 'VCPUs', 'CPU', 'State', 'Time(s)', 'CPU Affinity')
+
+    format = '%(name)-32s %(domid)3d %(number)5d %(c)5s %(s)5s ' \
+             ' %(cpu_time)8.1f %(cpumap)s'
 
     for dom in dominfo:
         def get_info(n):
@@ -568,10 +676,7 @@ def xm_vcpu_list(args):
                 c = "-"
                 s = "--p"
 
-            print (
-                "%(name)-32s %(domid)3d  %(number)4d  %(c)3s   %(s)-3s   %(cpu_time)7.1f  %(cpumap)s" %
-                locals())
-
+            print format % locals()
 
 def xm_reboot(args):
     arg_check(args, "reboot", 1, 3)
@@ -634,31 +739,31 @@ def xm_dump_core(args):
 
 def xm_rename(args):
     arg_check(args, "rename", 2)
-
+        
     server.xend.domain.setName(args[0], args[1])
 
-def xm_subcommand(command, args):
+def xm_importcommand(command, args):
     cmd = __import__(command, globals(), locals(), 'xen.xm')
     cmd.main([command] + args)
 
 
 #############################################################
 
-def cpu_make_map(cpulist):
-    cpus = []
-    for c in cpulist.split(','):
-        if c.find('-') != -1:
-            (x,y) = c.split('-')
-            for i in range(int(x),int(y)+1):
-                cpus.append(int(i))
-        else:
-            cpus.append(int(c))
-    cpus.sort()
-    return cpus
-
 def xm_vcpu_pin(args):
     arg_check(args, "vcpu-pin", 3)
 
+    def cpu_make_map(cpulist):
+        cpus = []
+        for c in cpulist.split(','):
+            if c.find('-') != -1:
+                (x,y) = c.split('-')
+                for i in range(int(x),int(y)+1):
+                    cpus.append(int(i))
+            else:
+                cpus.append(int(c))
+        cpus.sort()
+        return cpus
+
     dom  = args[0]
     vcpu = int(args[1])
     cpumap = cpu_make_map(args[2])
@@ -719,11 +824,12 @@ def xm_sched_sedf(args):
         info['period']  = ns_to_ms(info['period'])
         info['slice']   = ns_to_ms(info['slice'])
         info['latency'] = ns_to_ms(info['latency'])
-        print( ("%(name)-32s %(dom)3d %(period)9.1f %(slice)9.1f" +
+        print( ("%(name)-32s %(domid)3d %(period)9.1f %(slice)9.1f" +
                 " %(latency)7.1f %(extratime)6d %(weight)6d") % info)
 
     def domid_match(domid, info):
-        return domid is None or domid == info['name'] or domid == str(info['dom'])
+        return domid is None or domid == info['name'] or \
+               domid == str(info['domid'])
 
     # we want to just display current info if no parameters are passed
     if len(args) == 0:
@@ -757,20 +863,25 @@ def xm_sched_sedf(args):
         elif k in ['-w', '--weight']:
             opts['weight'] = v
 
-    # print header if we aren't setting any parameters
-    if len(opts.keys()) == 0:
-        print '%-33s %-2s %-4s %-4s %-7s %-5s %-6s'%('Name','ID','Period(ms)',
-                                                     'Slice(ms)', 'Lat(ms)',
-                                                     'Extra','Weight')
-
     doms = filter(lambda x : domid_match(domid, x),
                         [parse_doms_info(dom) for dom in getDomains("")])
+
+    # print header if we aren't setting any parameters
+    if len(opts.keys()) == 0:
+        print '%-33s %-2s %-4s %-4s %-7s %-5s %-6s' % \
+              ('Name','ID','Period(ms)', 'Slice(ms)', 'Lat(ms)',
+               'Extra','Weight')
+    
     for d in doms:
         # fetch current values so as not to clobber them
-        sedf_info = \
-            parse_sedf_info(server.xend.domain.cpu_sedf_get(d['dom']))
-        sedf_info['name'] = d['name']
+        try:
+            sedf_raw = server.xend.domain.cpu_sedf_get(d['domid'])
+        except xmlrpclib.Fault:
+            # domain does not support sched-sedf?
+            sedf_raw = {}
 
+        sedf_info = parse_sedf_info(sedf_raw)
+        sedf_info['name'] = d['name']
         # update values in case of call to set
         if len(opts.keys()) > 0:
             for k in opts.keys():
@@ -780,7 +891,7 @@ def xm_sched_sedf(args):
             v = map(int, [sedf_info['period'], sedf_info['slice'],
                           sedf_info['latency'],sedf_info['extratime'], 
                           sedf_info['weight']])
-            rv = server.xend.domain.cpu_sedf_set(d['dom'], *v)
+            rv = server.xend.domain.cpu_sedf_set(d['domid'], *v)
             if int(rv) != 0:
                 err("Failed to set sedf parameters (rv=%d)."%(rv))
 
@@ -789,17 +900,14 @@ def xm_sched_sedf(args):
             print_sedf(sedf_info)
 
 def xm_sched_credit(args):
-    usage_msg = """sched-credit:     Set or get credit scheduler parameters
- Usage:
-
-        sched-credit -d domain [-w weight] [-c cap]
-    """
+    """Get/Set options for Credit Scheduler."""
+    
     try:
-        opts, args = getopt.getopt(args[0:], "d:w:c:",
+        opts, params = getopt.getopt(args, "d:w:c:",
             ["domain=", "weight=", "cap="])
-    except getopt.GetoptError:
-        # print help information and exit:
-        print usage_msg
+    except getopt.GetoptError, opterr:
+        err(opterr)
+        usage('sched-credit')
         sys.exit(1)
 
     domain = None
@@ -816,15 +924,16 @@ def xm_sched_credit(args):
 
     if domain is None:
         # place holder for system-wide scheduler parameters
-        print usage_msg
+        err("No domain given.")
+        usage('sched-credit')
         sys.exit(1)
 
     if weight is None and cap is None:
         print server.xend.domain.sched_credit_get(domain)
     else:
-        err = server.xend.domain.sched_credit_set(domain, weight, cap)
-        if err != 0:
-            print err
+        result = server.xend.domain.sched_credit_set(domain, weight, cap)
+        if result != 0:
+            err(str(result))
 
 def xm_info(args):
     arg_check(args, "info", 0)
@@ -843,6 +952,8 @@ def xm_console(args):
     dom = args[0]
     info = server.xend.domain(dom)
     domid = int(sxp.child_value(info, 'domid', '-1'))
+    if domid == -1:
+        raise Exception("Domain is not started")
     console.execConsole(domid)
 
 def xm_uptime(args):
@@ -920,8 +1031,11 @@ its contents if the [-c|--clear] flag is specified.
     myargs = args
     myargs.insert(0, 'dmesg')
     gopts.parse(myargs)
-    if not (1 <= len(myargs) <= 2):
+    
+    if len(myargs) not in (1, 2):
         err('Invalid arguments: ' + str(myargs))
+        usage('dmesg')
+        sys.exit(1)
 
     if not gopts.vals.clear:
         print server.xend.node.dmesg.info()
@@ -939,7 +1053,7 @@ def xm_serve(args):
     from fcntl import fcntl, F_SETFL
     
     s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
-    s.connect(xen.xend.XendClient.XML_RPC_SOCKET)
+    s.connect(XendClient.XML_RPC_SOCKET)
     fcntl(sys.stdin, F_SETFL, os.O_NONBLOCK)
 
     while True:
@@ -1085,7 +1199,7 @@ def parse_block_configuration(args):
         cls = 'tap'
     else:
         cls = 'vbd'
-        
+
     vbd = [cls,
            ['uname', args[1]],
            ['dev',   args[2]],
@@ -1094,19 +1208,12 @@ def parse_block_configuration(args):
         vbd.append(['backend', args[4]])
 
     # verify that policy permits attaching this resource
-    try:
-        if security.on():
-            dominfo = server.xend.domain(dom)
-            label = security.get_security_printlabel(dominfo)
-        else:
-            label = None
+    if security.on():
+        dominfo = server.xend.domain(dom)
+        label = security.get_security_printlabel(dominfo)
+    else:
+        label = None
         security.res_security_check(args[1], label)
-    except security.ACMError, e:
-        print e.value
-        sys.exit(1)
-    except:
-        traceback.print_exc(limit=1)
-        sys.exit(1)
 
     return (dom, vbd)
 
@@ -1206,10 +1313,10 @@ commands = {
     "domid": xm_domid,
     "domname": xm_domname,
     "dump-core": xm_dump_core,
+    "reboot": xm_reboot,    
     "rename": xm_rename,
     "restore": xm_restore,
     "save": xm_save,
-    "reboot": xm_reboot,
     "shutdown": xm_shutdown,
     "uptime": xm_uptime,
     "list": xm_list,
@@ -1249,24 +1356,24 @@ commands = {
     }
 
 ## The commands supported by a separate argument parser in xend.xm.
-subcommands = [
+IMPORTED_COMMANDS = [
     'create',
     'migrate',
     'sysrq',
     'labels',
     'addlabel',
-    'rmlabel',
-    'getlabel',
-    'dry-run',
-    'resources',
     'cfgbootpolicy',
     'makepolicy',
     'loadpolicy',
     'dumppolicy'
+    'rmlabel',
+    'getlabel',
+    'dry-run',
+    'resources',
     ]
 
-for c in subcommands:
-    commands[c] = eval('lambda args: xm_subcommand("%s", args)' % c)
+for c in IMPORTED_COMMANDS:
+    commands[c] = eval('lambda args: xm_importcommand("%s", args)' % c)
 
 aliases = {
     "balloon": "mem-set",
@@ -1284,11 +1391,18 @@ def xm_lookup_cmd(cmd):
     elif aliases.has_key(cmd):
         deprecated(cmd,aliases[cmd])
         return commands[aliases[cmd]]
+    elif cmd == 'help':
+        longHelp()
+        sys.exit(0)
     else:
-        if len( cmd ) > 1:
-            matched_commands = filter( lambda (command, func): command[ 0:len(cmd) ] == cmd, commands.iteritems() )
-            if len( matched_commands ) == 1:
-		        return matched_commands[0][1]
+        # simulate getopt's prefix matching behaviour
+        if len(cmd) > 1:
+            same_prefix_cmds = [commands[c] for c in commands.keys() \
+                                if c[:len(cmd)] == cmd]
+            # only execute if there is only 1 match
+            if len(same_prefix_cmds) == 1:
+                return same_prefix_cmds[0]
+            
         err('Sub Command %s not found!' % cmd)
         usage()
 
@@ -1296,27 +1410,17 @@ def deprecated(old,new):
     print >>sys.stderr, (
         "Command %s is deprecated.  Please use xm %s instead." % (old, new))
 
-def usage(cmd=None):
-    if cmd == 'create':
-        mycmd = xm_lookup_cmd(cmd)
-        mycmd( ['--help'] )
-        sys.exit(1)
-    if help.has_key(cmd):
-        print "   " + help[cmd]
-    else:
-        print shorthelp
-    sys.exit(1)
-
 def main(argv=sys.argv):
     if len(argv) < 2:
         usage()
-    
-    if re.compile('-*help').match(argv[1]):
-	if len(argv) > 2:
-	    usage(argv[2])
-	else:
-	    usage()
-	sys.exit(0)
+
+    # intercept --help and output our own help
+    if '--help' in argv[1:]:
+        if '--help' == argv[1]:
+            longHelp()
+        else:
+            usage(argv[1])
+        sys.exit(0)
 
     cmd = xm_lookup_cmd(argv[1])
 
@@ -1329,9 +1433,9 @@ def main(argv=sys.argv):
                 usage()
         except socket.error, ex:
             if os.geteuid() != 0:
-                err("Most commands need root access.  Please try again as root.")
+                err("Most commands need root access. Please try again as root.")
             else:
-                err("Error connecting to xend: %s.  Is xend running?" % ex[1])
+                err("Unable to connect to xend: %s. Is xend running?" % ex[1])
             sys.exit(1)
         except KeyboardInterrupt:
             print "Interrupted."
@@ -1340,16 +1444,16 @@ def main(argv=sys.argv):
             if os.geteuid() != 0:
                 err("Most commands need root access.  Please try again as root.")
             else:
-                err("Error connecting to xend: %s." % ex[1])
+                err("Unable to connect to xend: %s." % ex[1])
             sys.exit(1)
         except SystemExit:
             sys.exit(1)
         except xmlrpclib.Fault, ex:
-            if ex.faultCode == xen.xend.XendClient.ERROR_INVALID_DOMAIN:
-                print  >>sys.stderr, (
-                    "Error: the domain '%s' does not exist." % ex.faultString)
+            if ex.faultCode == XendClient.ERROR_INVALID_DOMAIN:
+                err("Domain '%s' does not exist." % ex.faultString)
             else:
-                print  >>sys.stderr, "Error: %s" % ex.faultString
+                err(ex.faultString)
+            usage(argv[1])
             sys.exit(1)
         except xmlrpclib.ProtocolError, ex:
             if ex.errcode == -1:
@@ -1364,6 +1468,10 @@ def main(argv=sys.argv):
         except (ValueError, OverflowError):
             err("Invalid argument.")
             usage(argv[1])
+        except OptionError, e:
+            err(str(e))
+            usage(argv[1])
+            print e.usage()
         except:
             print "Unexpected error:", sys.exc_info()[0]
             print
diff --git a/tools/python/xen/xm/makepolicy.py b/tools/python/xen/xm/makepolicy.py
index 191566804d..5a8fa3d09b 100644
--- a/tools/python/xen/xm/makepolicy.py
+++ b/tools/python/xen/xm/makepolicy.py
@@ -20,7 +20,7 @@
 import sys
 import traceback
 from xen.util.security import ACMError, err, make_policy
-
+from xen.xm.opts import OptionError
 
 def usage():
     print "\nUsage: xm makepolicy <policy>\n"
@@ -29,13 +29,12 @@ def usage():
     err("Usage")
 
 
-
 def main(argv):
+    if len(argv) != 2:
+        raise OptionError('No XML policy file specified')
+
     try:
-        if len(argv) != 2:
-            usage()
         make_policy(argv[1])
-
     except ACMError:
         sys.exit(-1)
     except:
@@ -43,7 +42,6 @@ def main(argv):
         sys.exit(-1)
 
 
-
 if __name__ == '__main__':
     main(sys.argv)
 
diff --git a/tools/python/xen/xm/migrate.py b/tools/python/xen/xm/migrate.py
index 2b229c2632..b362ae9057 100644
--- a/tools/python/xen/xm/migrate.py
+++ b/tools/python/xen/xm/migrate.py
@@ -46,19 +46,17 @@ gopts.opt('resource', short='r', val='MBIT',
           fn=set_int, default=0,
           use="Set level of resource usage for migration.")
 
-def help(argv):
-    gopts.argv = argv
-    gopts.usage()
+def help():
+    return str(gopts)
     
 def main(argv):
     opts = gopts
     args = opts.parse(argv)
-    if opts.vals.help:
-        opts.usage()
-        return
+    
     if len(args) != 2:
-        opts.usage()
-        sys.exit(1)
+        raise OptionError('Invalid number of arguments')
+
     dom = args[0]
     dst = args[1]
-    server.xend.domain.migrate(dom, dst, opts.vals.live, opts.vals.resource, opts.vals.port)
+    server.xend.domain.migrate(dom, dst, opts.vals.live, opts.vals.resource,
+                               opts.vals.port)
diff --git a/tools/python/xen/xm/opts.py b/tools/python/xen/xm/opts.py
index e75af798ae..e0b650bbae 100644
--- a/tools/python/xen/xm/opts.py
+++ b/tools/python/xen/xm/opts.py
@@ -24,6 +24,46 @@ import os.path
 import sys
 import types
 
+def wrap(text, width = 70):
+    """ Really basic textwrap. Useful because textwrap is not available
+    for Python 2.2, and textwrap.wrap ignores newlines in Python 2.3+.
+    """
+    import string
+    
+    if len(text) < width:
+        return [text]
+    
+    lines = []
+    for line in text.split('\n'):
+        line = line.strip()
+        if len(line) < width:
+            lines.append(line)
+            continue
+        
+        pos = 0
+        while pos <= len(line):
+            wline = line[pos:pos+width].strip()
+            if len(wline) < 2:
+                break
+            
+            if wline[-1] in tuple(string.punctuation):
+                pos += width
+            else:
+                lastword = wline.split()[-1]
+                wline = wline[:-len(lastword)]
+                pos += width - len(lastword)
+            lines.append(wline)
+                
+    return lines
+
+class OptionError(Exception):
+    """Denotes an error in option parsing."""
+    def __init__(self, message, usage = ''):
+        self.message = message
+        self.usage = usage
+    def __str__(self):
+        return self.message
+
 class Opt:
     """An individual option.
     """
@@ -72,7 +112,21 @@ class Opt:
     def __repr__(self):
         return self.name + '=' + str(self.specified_val)
 
-    __str__ = __repr__
+    def __str__(self):
+        """ Formats the option into:
+        '-k, --key     description'
+        """
+        PARAM_WIDTH = 20
+        if self.val:
+            keys = ', '.join(['%s=%s' % (k, self.val) for k in self.optkeys])
+        else:
+            keys = ', '.join(self.optkeys)
+        desc = wrap(self.use, 55)
+        if len(keys) > PARAM_WIDTH:
+            desc = [''] + desc
+            
+        wrapped = ('\n' + ' ' * (PARAM_WIDTH + 1)).join(desc)
+        return keys.ljust(PARAM_WIDTH + 1) + wrapped
 
     def set(self, value):
         """Set the option value.
@@ -243,7 +297,19 @@ class Opts:
     def __repr__(self):
         return '\n'.join(map(str, self.options))
 
-    __str__ = __repr__
+    def __str__(self):
+        options = [s for s in self.options if s.optkeys[0][0] == '-']
+        optvals = [s for s in self.options if s.optkeys[0][0] != '-']
+        output = ''
+        if options:
+            output += '\nOptions:\n\n'
+            output += '\n'.join([str(o) for o in options])
+            output += '\n'
+        if optvals:
+            output += '\nValues:\n\n'
+            output += '\n'.join([str(o) for o in optvals])
+            output += '\n'
+        return output
 
     def opt(self, name, **args):
         """Add an option.
@@ -338,14 +404,14 @@ class Opts:
                                               self.short_opts(),
                                               self.long_opts())
             except getopt.GetoptError, err:
-                self.err(str(err))
+                raise OptionError(str(err), self.use)
+            #self.err(str(err))
                 
             for (k, v) in xvals:
                 for opt in self.options:
                     if opt.specify(k, v): break
                 else:
-                    print >>sys.stderr, "Error: Unknown option:", k
-                    self.usage()
+                    raise OptionError('Unknown option: %s' % k, self.use)
 
             if not args:
                 break
@@ -390,10 +456,10 @@ class Opts:
     def usage(self):
         print 'Usage: ', self.argv[0], self.use or 'OPTIONS'
         print
-        for opt in self.options:
-            opt.show()
-            print
         if self.options:
+            for opt in self.options:
+                opt.show()
+                print
             print
 
     def var_usage(self):
@@ -427,7 +493,9 @@ class Opts:
                 self.load(p, help)
                 break
         else:
-            self.err('Cannot open config file "%s"' % self.vals.defconfig)
+            raise OptionError('Unable to open config file: %s' % \
+                              self.vals.defconfig,
+                              self.use)
 
     def load(self, defconfig, help):
         """Load a defconfig file. Local variables in the file
@@ -478,9 +546,9 @@ def set_false(opt, k, v):
 def set_bool(opt, k, v):
     """Set a boolean option.
     """
-    if v in ['yes']:
+    if v in ('yes', 'y'):
         opt.set(1)
-    elif v in ['no']:
+    elif v in ('no', 'n'):
         opt.set(0)
     else:
         opt.opts.err('Invalid value:' +v)
diff --git a/tools/python/xen/xm/resources.py b/tools/python/xen/xm/resources.py
index c3a83a5f29..c0ddeb5560 100644
--- a/tools/python/xen/xm/resources.py
+++ b/tools/python/xen/xm/resources.py
@@ -21,13 +21,12 @@
 import sys
 from xen.util import dictio
 from xen.util import security
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm resource\n"
-    print "  This program lists information for each resource in the"
-    print "  global resource label file\n"
-    security.err("Usage")
-
+def help():
+    return """Usage: xm resource
+    This program lists information for each resource in the
+    global resource label file."""
 
 def print_resource_data(access_control):
     """Prints out a resource dictionary to stdout
@@ -38,11 +37,16 @@ def print_resource_data(access_control):
         print "    policy: "+policy
         print "    label:  "+label
 
-
 def main (argv):
+    if len(argv) > 1:
+        raise OptionError("No arguments required")
+    
     try:
-        if len(argv) != 1:
-            usage()
+        filename = security.res_label_filename
+        access_control = dictio.dict_read("resources", filename)
+    except:
+        print "Resource file not found."
+        return
 
         try:
             file = security.res_label_filename
@@ -52,9 +56,6 @@ def main (argv):
 
         print_resource_data(access_control)
 
-    except security.ACMError:
-        sys.exit(-1)
-
 if __name__ == '__main__':
     main(sys.argv)
 
diff --git a/tools/python/xen/xm/rmlabel.py b/tools/python/xen/xm/rmlabel.py
index e9df1ad573..0d0993b6e5 100644
--- a/tools/python/xen/xm/rmlabel.py
+++ b/tools/python/xen/xm/rmlabel.py
@@ -21,15 +21,17 @@
 import sys, os, re
 from xen.util import dictio
 from xen.util import security
+from xen.xm.opts import OptionError
 
-def usage():
-    print "\nUsage: xm rmlabel dom <configfile>"
-    print "       xm rmlabel res <resource>\n"
-    print "  This program removes an acm_label entry from the 'configfile'"
-    print "  for a domain or from the global resource label file for a"
-    print "  resource. If the label does not exist for the given domain or"
-    print "  resource, then rmlabel fails.\n"
-    security.err("Usage")
+def help():
+    return """
+    Example: xm rmlabel dom <configfile>
+             xm rmlabel res <resource>
+
+    This program removes an acm_label entry from the 'configfile'
+    for a domain or from the global resource label file for a
+    resource. If the label does not exist for the given domain or
+    resource, then rmlabel fails."""
 
 
 def rm_resource_label(resource):
@@ -93,23 +95,23 @@ def rm_domain_label(configfile):
 
 
 def main (argv):
-    try:
-        if len(argv) != 3:
-            usage()
 
+    if len(argv) != 3:
+        raise OptionError('Requires 2 arguments')
+    
+    if argv[1].lower() not in ('dom', 'res'):
+        raise OptionError('Unrecognised type argument: %s' % argv[1])
+
+    try:
         if argv[1].lower() == "dom":
             configfile = argv[2]
             rm_domain_label(configfile)
         elif argv[1].lower() == "res":
             resource = argv[2]
             rm_resource_label(resource)
-        else:
-            usage()
-
     except security.ACMError:
         sys.exit(-1)
 
-
 if __name__ == '__main__':
     main(sys.argv)
 
diff --git a/tools/python/xen/xm/sysrq.py b/tools/python/xen/xm/sysrq.py
index 67db732757..d17596f707 100644
--- a/tools/python/xen/xm/sysrq.py
+++ b/tools/python/xen/xm/sysrq.py
@@ -19,14 +19,12 @@ gopts.opt('help', short='h',
 def main(argv):
     opts = gopts
     args = opts.parse(argv)
-    if opts.vals.help:
-        opts.usage()
-        return
-        
-    # no options for the moment
-    if len(args) != 2:
-        opts.usage()
-        sys.exit(1)
+
+    if len(args) < 1:
+        raise OptionError('Missing domain argument')
+    if len(args) < 2:
+        raise OptionError('Missing sysrq character')
+
     dom = args[0]
     req = ord(args[1][0])
     server.xend.domain.send_sysrq(dom, req)
-- 
2.30.2