apache2 virtual host

["Russell L. Harris" <russell@rlharris.org>]

I receive the following error message when attempting to enable a
virtual host (apache2 in Debian 10):

   root@penelope:/etc/apache2/sites-available# a2ensite domain1.com.conf
   bash: a2ensite: command not found

The configuration file domain1.com.conf is owned by root:root and has
permissions identical to those of 000-default.conf .

The man page for a2ensite prints, so I do not understand why bash
cannot find the command.

I have tried (without success):

  # a2ensite domain1
  # a2ensite domain1.com
  # a2ensite domain1.com.conf