can't generate key via dnssec-keygen

$ dnssec-keygen -a HMAC-MD5 -b 512 -n HOST {host} above results in blank line and endless waiting $ dnssec-keygen -T DNSKEY -a HMAC-MD5 -b 512 -n HOST {host} the same entropy: $ cat /proc/sys/kernel/random/entropy_avail 890 ps. I was trying to make some noise by **find /** but that brought no result