Though the default for the `fqdn` value is listed as `both` in
*dhcpcd.conf(5)*, the current behavior of `dhcpcd` suggests that it may
actually be `none`. Without explicitly setting `fqdn both`, the value of
the kernel node name is sent as-is in the *hostname* option (12). If the
node name is set to the FQDN, then dynamic DNS gets broken, since the
DHCP server always appends its domain name to the provided hostname.
Setting `fqdn both` causes `dhcpcd` to send the FQDN in the *FQDN*
option (81), which the DHCP server interprets correctly.
Using a list to specify the values for the `allowinterfaces` and
`denyinterfaces` parameters in `dhcpcd.conf` makes the configuration
policy cleaner and more type-safe.
Today I realized that `dhcpcd` has been logging several hundred thousand
of these messages every second:
libudev: received NULL device
This was causing both `dhcpcd` and `systemd-journald` to consume 100%
CPU.
I am not entirely sure what a "device management" module is in the
context of `dhcpcd`, but it does not seem to be required. Setting the
`nodev` option in `dhcpcd.conf` suppresses the messages, and seems to
have no effect on the operation of the daemon.
Dustin