def start_vm(self, disable_ipv6=True):
        """Starts guest VM.

        :param: Disable IPv6 on eth0.
        """

        log.info(
            f'Requested: {self._arch}, {self._bit}-bit, {self._endian} endian.'
        )

        self._proc = pexpect.spawn(
            self._run_cmd, encoding='utf-8', timeout=self._file.exec_time+50
        )
        self._proc.logfile = open(
            f'{self._file.data_dir}/machine.log', 'w', encoding='utf-8'
        )

        # login
        self._proc.expect('login: ')
        self._proc.sendline('root')
        self._proc.expect('[pP]assword: ')
        self._proc.sendline('root')
        self._proc.expect(self._prompt)

        self._is_running = True

        if disable_ipv6:
            self.send_command(
                'echo 1 > /proc/sys/net/ipv6/conf/eth0/disable_ipv6'
            )
Starts guest VM.

        :param: Disable IPv6 on eth0.
        
lisa/core/qemu_guest.py