Detecting the init.d command:

CHKCONFIG       := $(wildcard /sbin/chkconfig) 
UPDATE_RCD      := $(wildcard /usr/sbin/update-rc.d) 
ifdef CHKCONFIG
  ADD_INITD     := $(CHKCONFIG) --add zaptel
else
  ifdef $(UPDATE_RCD)
    ADD_INITD   := $(UPDATE_RCD) zaptel defaults 15 30
  endif
endif

...


config:
        if [ -d $(INSTALL_PREFIX)/etc/rc.d/init.d ]; then \
                install -D -m 755 zaptel.init $(INSTALL_PREFIX)/etc/rc.d/init.d/
zaptel; \
        elif [ -d $(INSTALL_PREFIX)/etc/init.d ]; then \
                install -D -m 755 zaptel.init $(INSTALL_PREFIX)/etc/init.d/zapte
l; \
        fi
ifdef ADD_INITD
        $(ADD_INITD)
endif