Bonno Bloksma:
There is the strange fact that it seems the config is tested twice but
I guess systemd will try to start a service twice before giving up.
I recommend less guessing and more reading your own posts. (-: You
yourself posted the very script fragment where /the script itself/ runs
the test command twice:
test_config()
{
if ! /usr/sbin/dhcpd -t $OPTIONS -q -cf "$DHCPD_CONF" > /dev/null
2>&1; then
echo "dhcpd self-test failed. Please fix $DHCPD_CONF."
echo "The error was: "
/usr/sbin/dhcpd -t $OPTIONS -cf "$DHCPD_CONF"
exit 1
fi
}
See where that runs |/usr/sbin/dhcpd| in test mode twice? The first
time, dhcpd writes the error message to the syslog; the second time
|dhcpd| writes the error message to its standard error. Both lots of
output end up in the journal.
From the LSB: prefix to the service name in the very log output that
you posted, we can deduce that systemd is running your van Smoorenburg
|rc| script as a service, wrapping it in a nonce service unit
<https://unix.stackexchange.com/a/233581/5132>. The test performed by
the van Smoorenburg |rc| script is considered to /be a part of your
service/. By the time that the script is running, and executing the
startup test, systemd thinks that your service is already running. The
stop and start actions of systemd encompass the script as a whole, and
operate outwith the configuration validation test, not within it.
Put another way: There is no customizable mechanism to make the very
execution of the start, stop, and restart commands in systemd dependent
from first testing some arbitrary service-specific condition. There's
no way to tell systemd "only actually execute the restart command at all
if this shell script first returns true". When running restart, systemd
will stop your service, start it again, and the test in the script will
/only then/ run as part of your service's initialization.
The best that you have are mechanisms that cause a startup to abort, by
failing an ExecStartPre command. But for those you must actually write
a proper service unit file. |systemd-sysv-generator| employs a
one-size-fits-all approach, and will not generate such service-specific
special-case stuff in the nonce units that it generates for van
Smoorenburg |rc| scripts. You need a bona fide human being to actually
write a service unit file. Even then, that is not enough. A restart
will still stop the service /before/ the ExecStartPre tests are run, and
you won't get what you want. restart is stop /then/ start.
