If +x isn't set on the parent directory of resolved.conf, systemd-resolved seems to fail to start. The error message I get is: Failed to open configuration file /etc/systemd/resolved.conf: Permission denied This is also repeatable if invoking the systemd-resolved binary directly, without using systemctl. But what really is wrong is that +x isn't set on the parent directory /etc/systemd, changing any permissions on the file itself doesn't help. Perhaps systemd-resolved could access this file without +x on the parent directory, or at least warn that the permissions on the parent directory are wrong?
This was changed in http://cgit.freedesktop.org/systemd/systemd/commit/?id=74b2466e14. systemd-resolved will now loudly complain, but continue. But in general, for most daemons it makes sense to fail to start if their configuration files are mangled or otherwise broken, as this means that there's a problem that needs to be fixed, and often it is better to abort then delived half-broken results, so this change might get reverted. Also, systemd-resolved simply tries to open the file using a direct open() call. If the kernel does not allow that, then the daemon cannot do anything about it.
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