How do I use Drush 8 site aliases in Drush 9? In Drush 8, my site aliases are loaded correctly from ~/.drush/mysite.aliases.drushrc.php.

E.g.

$aliases['dev'] = array(
  'root' =&gt; '/var/www/html/mysite.dev/docroot',
  'uri' =&gt; 'mysite.prod.acquia-sites.com',
  'remote-host' =&gt; 'mysite.ssh.acquia-sites.com',
  'remote-user' =&gt; 'mysite.dev',
  'path-aliases' =&gt; array(
    '%drush-script' =&gt; 'drush' . $drush_major_version,
  ),
);


However these aliases aren't loaded in Drush 9.

$ drush site-alias
{  }


How I should define site aliases in Drush 9? Is there any migration process?
Aliases are now provided in YAML files. According to the example aliases file for Drush 9:


  To convert legacy alias (*.aliases.drushrc.php) to yml, run the site:alias-convert command.


So running the command:

drush site:alias-convert


should do the trick.