Drush pm-update (bootstrap error)

# yum install git
...
## drush-master a github-ról ---> /opt/drush7

curl -sS https://getcomposer.org/installer | php
mv composer.phar composer
cd /opt/drush7
composer install
 
# /opt/drush7/drush version
 Drush Version   :  7.0-dev

<?php
 
$aliases['siteA'] = array(
  'uri'  => 'localhost',
  'root' => '/var/www/vhosts/drupal7',
  'db-url' => 'mysql://DBUSER:DBPASS@localhost/DBNAME',
);
 
$aliases['allsites'] = array('site-list' => array('@siteA'),);
?>

# /opt/drush7/drush pm-update
Command pm-update needs a higher bootstrap level to run - you will need to invoke drush from a more functional Drupal environment to run this command.                                                                                                             [error]
The drush command 'pm-update' could not be executed.                                                                                                                                                                                                               [error]
Drush was not able to start (bootstrap) the Drupal database.                                                                                                                                                                                                       [error]
Hint: This may occur when Drush is trying to:
 * bootstrap a site that has not been installed or does not have a configured database. In this case you can select another site with a working database setup by specifying the URI to use with the --uri parameter on the command line. See `drush topic
docs-aliases` for details.
 * connect the database through a socket. The socket file may be wrong or the php-cli may have no access to it in a jailed shell.
 
Drush was attempting to connect to: 
 Drupal version         :  7.34                                        
 Site URI               :  http://default                              
 PHP executable         :  /usr/bin/php                                
 PHP configuration      :  /etc/php.ini                                
 PHP OS                 :  Linux                                       
 Drush version          :  7.0-dev                                     
 Drush temp directory   :  /tmp                                        
 Drush configuration    :                                              
 Drush alias files      :  /opt/drush7/includes/../aliases.drushrc.php 
 Drupal root            :  /var/www/vhosts/drupal7
 Site path              :  sites/default