A: The recommended way is to copy the service file from /usr/lib/systemd/system to /etc/systemd/system and edit it there. The latter directory takes precedence over the former, and rpm will never overwrite it. If you want to use the distributed service file again you can simply delete (or rename) the service file in /etc/systemd/system again.
I think I got bit yesterday by the above...I was noticing terrible resolution speed, so checked messages (btw, "service bind9 status" provides brief, but decent-ish characterization of things), and noticed many messages indicating failing resolutions against IPv6 addresses.There is a common pair of bits of Bind configuration:a) One might set options to prefer not to use IPv6 addresses, so in /etc/bind/named.conf.options, changelisten-on-v6 { all;};tolisten-on-v6 { none; };b) This was where SystemD got into the mix...Pass the "-4" option when running named to use only IPv4. This seems to be the highly significant bit.On Debian-derived systems, the usual recipe is to add "-4" to /etc/defaults/bind--> OPTIONS="-4"However, the SystemD config for Bind9 lives in /lib/systemd/system/bind9.service, and apparently there is recent change there that that configuration no longer reads from /etc/defaults/bind, so that to have named get the "-4" option requires altering /lib/systemd/system/bind9.service. Seems like it needs to be altered directly.This isn't necessarily a "SystemD bug", rather a packaging bug in Debian. It still was fairly annoying.I have yet to report it properly, probably deserves a bit more research, in case my diagnosis is off a bit.
--
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"
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