CAP_KILL seems a bit too much privileges for the sole purpose of being able to make ExecReload= work.
Use the + prefix on ExecReload= instead to run "/bin/kill -HUP $MAINPID" with full privileges, ignoring the restrictions from CapabilityBoundingSet=.
See https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStart= for further details about the + prefix in ExecReload=.
The ExecReload command calls kills on a process owned by the unbound user (or whatever user is configured). To do so, it needs the CAP_KILL capability.
This is needed when unbound config doesn't set "do-daemonize: no" by itself otherwise starting service fails with:
systemd[1]: unbound.service: Got notification message from PID <PID>, but reception only permitted for main PID which is currently not known
https://github.com/NLnetLabs/unbound/blob/release-1.9.3/doc/example.conf.in#L236
Since kernel 3.2, CAP_NET_RAW instead of CAP_NET_ADMIN is sufficient to allow for the usage of the IP_TRANSPARENT socket option. CAP_NET_ADMIN allows far more mayhem then CAP_NET_RAW, so prefer the safer, more restrictive solution.
Make it more consistent throughout the man page.
If a config option can either be *yes* or *no* use exact these terms and not something like *on* which could be easily read as *no*.
1. Remove `ProtectKernelTunables=true`: This prevents various with socket options from working as shown below.
`unbound[] warning: so-rcvbuf 1048576 was not granted. Got 425984. To fix: start with root permissions(linux) or sysctl bigger net.core.rmem_max(linux) or kern.ipc.maxsockbuf(bsd) values.`
2. Add `CAP_NET_ADMIN` to available caps which is needed for `ip-transparent: yes` config option to work as shown below.
`unbound[] warning: setsockopt(.. IP_TRANSPARENT ..) failed: Operation not permitted`
3. Make `ReadWritePaths` less permissive: `UNBOUND_SYSCONF_DIR` equals to `sysconfdir` which usually equals to `/etc` and `UNBOUND_LOCALSTATE_DIR` equals to `localstatedir` which usually equals to `/var`. Allowing write access for those dirs shouldn't be needed. The only dirs unbound should be allow to write to are `/run` ( for pidfile), `@UNBOUND_RUN_DIR@` (for chroot) and `@UNBOUND_CHROOT_DIR@` in case it differs from the previous one.
4. Bind-mount `/run/systemd/notify`, `UNBOUND_PIDFILE`, `/dev/log`, `/dev/urandom` in order to use them inside chroot.
5. Add few extra hardening options: `RestrictNamespaces`, `LockPersonality` and `RestrictSUIDSGID` should be safe to use.
on low verbosity, they show on verbosity 3 (query details), because
there is a high volume and the operator cannot do anything for the
remote failure. Specifically filters the high volume errors.
