UnixSocketDir
UnixSocketDir <Apache user home directory> Default none Server
This directive gives mod_backhand
a directory
where it can write a file containing the performance details of this
server — known as the “Arriba”.
Since mod_backhand
has the permissions of Apache,
this directory needs to be writable by webuser/webgroup — or
whatever user/group you have configured Apache to run as. You might
want to create a subdirectory /backhand beneath
the Apache user’s home directory, for example.