FreeNAS is basically a web frontend to BSD-backed ZFS volumes,
filesystems, and various ways to share them (i.e., iSCSI, NFS, etc).
It stores all its config info in a sqlite DB from which it configs
the BSD system.  It uses Django (a slightly weird MVC that exports a web
interface; logic/models/views are all in python, and there is an
HTML-based template interface.

What I did was basically to wrap the model/form parts of FreeNAS's
code -- so for the commands we want to support, we actually mock up
an HTTP request, and submit it directly to the correct handler function
that the FreeNAS Django config files specify.  This allows us to leverage
all the FreeNAS error checking code and automation (i.e., deleting an
interface would delete aliases on that interface too).

usage() prints this, at present:

Supply a command set class, an operation, and the necessary arguments.

  interface       Configure network interfaces
    add  <interface> <name> [<dhcp=X> <ipv6auto=X> <options=X> ] ...
    del  <interface>
    edit <interface> [<dhcp=X> <ipv6auto=X> <name=X> <options=X> ] ...
  ist             Configure ISCSI targets (a target binds SCSI attributes
         (i.e. serial number, r/w flags, queue depth, block size) to iSCSI
         attributes (i.e., a target portal, authorized initiator network ACLs,
         iSCSI authentication info)
    add  <name> <serial> <portalgroup> <initiatorgroup> [<authtype>
         <authgroup> ] [<alias=X> <flags=X> <logical_blocksize=X>
         <queue_depth=X> <type=X> ]
    del  <name>
    edit <name> [<serial> <portalgroup> <initiatorgroup> <authtype>
         <authgroup> ]
  ist_assoc       Associate extents with targets (final "link" between storage
         and network)
    add <target> <extent>
    del <target> <extent>
  ist_authcred    Configure ISCSI target authentication credentials (i.e.,
         users)
    add  <tag> <user> <secret1> [<peeruser> <peersecret1> ]
    del  <user>
    edit <tag> <user> <secret1> [<peeruser> <peersecret1> ]
  ist_authinit    Configure ISCSI initiator authorizations by hostname or
         network
    add  <tag> <initiators> [<auth_network> <comment> ]
    del  <tag>
    edit <tag> <initiators> [<auth_network> <comment> ]
  ist_config      Configure general ISCSI parameters
    edit [<basename=X> <defaultt2r=X> <defaultt2w=X> <discoveryauthgroup=X>
         <discoveryauthmethod=X> <firstburst=X> <iotimeout=X> <maxburst=X>
         <maxconnect=X> <maxoutstandingr2t=X> <maxrecdata=X> <maxsesh=X>
         <nopinint=X> <r2t=X> ]
  ist_extent      Configure ISCSI target extents (block devs or files exported
         via ISCSI)
    add      <name> <dev> [<comment> ]
    addfile  <name> <path> <filesize> [<comment> ]
    del      <name>
    edit     <name> <dev> [<comment> ]
    editfile <name> <path> [<comment> ] [<filesize=X> ]
  ist_portal      Configure ISCSI target portals (i.e., ip:port binding to
         associate with a target)
    add  <tag> [<comment=X> ] ...
    del  <tag>
    edit <tag> [<comment=X> ] ...
  network         Configure generic network settings
    config [<domain=X> <hostname=X> <ipv4gateway=X> <ipv6gateway=X>
         <nameserver1=X> <nameserver2=X> <nameserver3=X> ]
  pool            Configure ZFS storage pools
    add <volume_name> <volume_fstype> <group_type>  ...
    del <vol_name>
    mod <volume_add> <volume_fstype> <group_type>  ...
  route           Configure static routes
    add <destination> <gateway> [<description> ]
    del <destination> [<gateway> ]
  snapshot        Create, clone, rollback ZFS snapshots of volumes or clones
    add      <snap_name>
    clone    <cs_snapshot> <cs_name>
    del      <snap_name>
    rollback <snap_name>
  vlan            Configure vlan interfaces
    add <pint> <vint> <tag> [<description> ]
    del <vint>
  volume          Configure ZFS volumes (zvols) atop pools
    add <pool_name> <zvol_name> <zvol_size> <zvol_compression>
    del <pool_name> <vol_name>