Virtualisation service for use via userv
----------------------------------------

adt-virt-xenlvm supports use of Xen virtual machines and LVM COW via
the userv `security boundary tool'.  By default the files
corresponding to this setup are installed but not enabled.

What is provided to non-root accounts is the ability to start the
testbed and run commands on it (functionality equivalent to
adt-xenlvm-with-testbed and adt-xenlvm-on-testbed) but not the ability
to create new testbeds.

To make this feature available:
 * Install userv.
 * Create a group named AdtXenUs containing the users which should
   be able to manipulate and use the testbed.
 * Collect the public ssh key(s) of the user(s) and put them in
   /etc/autopkgtest/xenlvm_adt_sshauthkeys (this will allow them
   to ssh to root@testbed).
 * Run adt-xenlvm-setup.  NB that the contents of the _sshauthkeys
   file (above) are copied into the testbed by adt-xenlvm-setup;
   any changes mean that setup needs to be run again.

Typically adt-xenlvm-setup ought to be run periodically anyway to
make sure that the snapshot doesn't get too out of date.


Client interface
----------------

The service is as invoked as
  userv [-Ddistro=<distro> -Dnominum=<nominum>] \
        [-Dssh_privkey=...|-Dssh_keyident_args=...] \
	root adt-xenlvm-testbed <act>
where <act> is one of
  with
	Starts adt-xenlvm-with-testbed, prints `y', waits for
	eof on stdin, and then exits adt-xenlvm-with-testbed.
  pon0
	Prints the command that ought to be run to execute
	commands on the testbed.  The output is a command and
	arguments, each followed by a null byte.  These should
	be put into an array of strings and passed to exec,
	with the actual command to be run added as a final
	argument (in sh syntax).
  console
	Runs  xm console <name-of-guest>
	(NB without a pty).

Only guests for which
  /var/lib/autopkgtest/xenlvm/<nominum>_<distro>
exists and is a directory are allowed.