File entrypoint.sh of Package bind-image
#!/bin/bash
set -euo pipefail
if [ $# -gt 0 ]; then
# launched via entrypoint.sh foo bar => execute the args
exec "$@"
else
# mimic what named.service does
/usr/local/lib/bind/named.prep
exec /usr/sbin/named -u named -fg -c "${NAMED_CONF}" ${NAMED_ARGS:+ "$NAMED_ARGS"}
fi