===
xm migrate	: 
1) [./tools/python/xen/xm/migrate.py]	
	calls server.xend.domain.migrate(dom, dst, opts.vals.live, opts.vals.resource, opts.vals.port)	
	(server <-- import from xen.xend.XendClient import server)
	xen.xend.XendClient
				from xen.util.xmlrpclib2 import ServerProxy
				server = ServerProxy('httpu:///var/run/xend/xmlrpc.sock')
2) [./tools/python/xen/xend/XendDomain.py]
	(def) domain_migrate() (called supposedly as per #1)
	a) create a TCP connection with the destn
	b) send a 'receive' packet on port 8002
		RECEIVING SIDE:
		===============
		- this is received in dataReceived() method of web/connection.py & delegates to next step
		- dataReceived() method of /tools/python/xen/xend/server/relocate.py is invoked
		- op_receive() method in relocate.py calls XendDomain.domain_restore_fd()
		- XendDomain.py calls XendCheckpoint.restore(self, fd)
		- XendCheckpoint.restore(self, fd)
			validate SIGNATURE
			validate config file
			dominfo = xd.restore_(vmconfig)		(xd = XendDomain)
				dominfo = XendDomainInfo.restore(config)
				self._add_domain(dominfo)
				return dominfo	
			validate pfn_count
			calls xc_restore executable
			dominfo.unpause()
			dominfo.completeRestore(...)
	f) XendDomain.py calls save() method of (3)
		 XendCheckpoint.save(sock.fileno(), dominfo, live)
	//sock.fileno() is the file opened on the other side.
	[for xm save, this is just a file opend locally] < ==
	fd = os.open(dst, os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
		write_exact(fd, SIGNATURE, "could not write guest state file: signature")	[/tools/python/xen/xend/XendCheckpoint.py]
		write_exact(fd, pack("!i", len(config)), "could not write guest state file: config len");
		write_exact(fd, config, "could not write guest state file: config")
3) [./tools/python/xen/xend/XendCheckpoint.py]
	(def) save(fd, dominfo, live) (called as per #2)
		==>starts writing out stuff into the file!! [<=====NOTE LinuxGuestRecord]
		==> calls /usr/lib64/xen/bin/xc_save executable in a thread
			[built from tools/xcutils/xc_save.c]	
				==>calls xc_linux_save (xc_fd, io_fd, domid, maxit, max_f, flags, &suspend);

4) [./tools/libxc/xc_linux_save.c]
	(def) xc_linux_save




======
Image file structure:
write_exact(fd, SIGNATURE, "could not write guest state file: signature")	[/tools/python/xen/xend/XendCheckpoint.py]
write_exact(fd, pack("!i", len(config)), "could not write guest state file: config len");
write_exact(fd, config, "could not write guest state file: config")

max_pfn:	write_exact(io_fd, &max_pfn, sizeof(unsigned long))
p2m_frame_list:	write_exact(io_fd, p2m_frame_list, P2M_FL_SIZE

/*Now write out each data page, canonicalising page tables as we go... */