When issuing `/etc/init.d/exim4 what'' in the terminal, a `User defined signal 1'' message is printed. Clearly, the signal is sent by exiwhat, which is run by the what argument to /etc/init.d/exim4. Yet, when exiwhat is run from the command line, no `User defined signal 1'' message is printed. Which makes me think that the message is printed by the init script. But I can not see where that message is being printed by the init script. Any insight? Note that for some reason, the return code of `/etc/init.d/exim4 what'' is 138. Which is probably because a signal is involved. I think the problem here is that according to invoke-rc.d man page, such return code is reserved in Debian and by the LSB, and should not be returned by an init script. Rethinking, perhaps an init script should be explicitly filtered from the processes to which exiwhat is sending its -USR1 signal? This might be achieved by instructing the killall command in exiwhat to use the --user Debian-exim switch.