provided by Star2Billing S.L.

Is there any doc on installation callback on Debian?

Do the instructions in addons/Doc/Callback-Install.info not work on Debian?

Sort of. I didn't have any trouble to install it on CentOS. But this time I'm installing a2billing on Debian.
I did follow the instruction to "install --owner=root --group=root --mode=700 a2billing-callback-daemon /usr/local/bin/"
then, start the daemon by execute:
/usr/local/bin/a2billing-callback-daemon

Finally, I found to make callback work, I have to manually change
$dbh ||= DBI->connect("dbi:mysql:$dbname:$dbhost", "$login", "$pwd");
to add in my actual dbname, dbhost, login, pwd to make the daemon work.
I don't know what I have missed.