These options can be set via the environment variable -e flag. The configuration can be extended by dropping files as /etc/unbound/conf.d/*.conf
DO_IPV6: Enable or disable ipv6. (Default: "yes", Possible Values: "yes, no")
DO_IPV4: Enable or disable ipv4. (Default: "yes", Possible Values: "yes, no")
DO_UDP: Enable or disable udp. (Default: "yes", Possible Values: "yes, no")
DO_TCP: Enable or disable tcp. (Default: "yes", Possible Values: "yes, no")
VERBOSITY: Verbosity number, 0 is least verbose. (Default: "0", Possible Values: "")
NUM_THREADS: Number of threads to create. 1 disables threading. (Default: "1", Possible Values: "")
SO_RCVBUFF: Buffer size for UDP port 53 incoming. Use 4m to catch query spikes for busy servers. (Default: "0", Possible Values: "")
SO_SNDBUF: Buffer size for UDP port 53 outgoing. Use 4m to handle spikes on very busy servers. (Default: "0", Possible Values: "")
SO_REUSEPORT: Use SO_REUSEPORT to distribute queries over threads. (Default: "no", Possible Values: "yes, no")
EDNS_BUFFER_SIZE: EDNS reassembly buffer to advertise to UDP peers. 1480 can solve fragmentation (timeouts). (Default: "4096", Possible Values: "")
MSG_CACHE_SIZE: The amount of memory to use for the message cache. Plain value in bytes or you can append k, m or G. (Default: "4m", Possible Values: "")
RRSET_CACHE_SIZE: The amount of memory to use for the RRset cache. Plain value in bytes or you can append k, m or G. (Default: "4m", Possible Values: "")
CACHE_MIN_TTL: The time to live (TTL) value lower bound, in seconds. If more than an hour could easily give trouble due to stale data. (Default: "0", Possible Values: "")
CACHE_MAX_TTL: The time to live (TTL) value cap for RRsets and messages in the cache. Items are not cached for longer. In seconds. (Default: "86400", Possible Values: "")
CACHE_MAX_NEGATIVE_TTL: The time to live (TTL) value cap for negative responses in the cache. (Default: "3600", Possible Values: "")
HIDE_IDENTITY: Enable to not answer id.server and hostname.bind queries. (Default: "no", Possible Values: "yes, no")
HIDE_VERSION: Enable to not answer version.server and version.bind queries. (Default: "no", Possible Values: "yes, no")
STATISTICS_INTERVAL: print statistics to the log (for every thread) every N seconds. (Default: "0", Possible Values: "0, 1")
STATISTICS_CUMULATIVE: enable cumulative statistics, without clearing them after printing. (Default: "no", Possible Values: "yes, no")
EXTENDED_STATISTICS: enable extended statistics (query types, answer codes, status) printed from unbound-control. (Default: "no", Possible Values: "yes, no")
INTERFACE: Sets the interface to listen on useful when using --net=host (Default 0.0.0.0, Possible Values: "", "@")
UPSTREAM_PORT: The port the upstream is using for DNS over TLS, default 853
UPSTREAM_HOST: The host to use for upstream DNS over TLS, default is UncensoredDNS. Must be an IP address
CONTROL_ENABLE: Enable Unound's control interface. Default is no
CONTROL_INTERFACE: Which interface to bind the control interface to, if enabled. Default is 0.0.0.0
USE_SYSLOG: Log to syslog. Default is no since Unbound already logs to sdtout when running with daemon=no.