docker search コマンドを使って、Docker Hub（レジストリ）で公開されているイメージを検索することができます。
次の例では、ubuntu というキーワードでイメージを検索しています。
Docker Hub 上で付けられたスターの数や、公式イメージかどうかもチェックできます。
$ docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating sys… 14524 [OK]
websphere-liberty WebSphere Liberty multi-architecture images … 286 [OK]
ubuntu-upstart DEPRECATED, as is Upstart (find other proces… 112 [OK]
neurodebian NeuroDebian provides neuroscience research s… 91 [OK]
open-liberty Open Liberty multi-architecture images based… 53 [OK]
ubuntu/nginx Nginx, a high-performance reverse proxy & we… 52
ubuntu-debootstrap DEPRECATED; use "ubuntu" instead 46 [OK]
ubuntu/apache2 Apache, a secure & extensible open-source HT… 36
ubuntu/mysql MySQL open source fast, stable, multi-thread… 34
kasmweb/ubuntu-bionic-desktop Ubuntu productivity desktop for Kasm Workspa… 29
ubuntu/prometheus Prometheus is a systems and service monitori… 27
ubuntu/squid Squid is a caching proxy for the Web. Long-t… 25
ubuntu/bind9 BIND 9 is a very flexible, full-featured DNS… 22
ubuntu/postgres PostgreSQL is an open source object-relation… 17
ubuntu/redis Redis, an open source key-value store. Long-… 10
ubuntu/grafana Grafana, a feature rich metrics dashboard & … 6
ubuntu/prometheus-alertmanager Alertmanager handles client alerts from Prom… 6
ubuntu/kafka Apache Kafka, a distributed event streaming … 6
ubuntu/memcached Memcached, in-memory keyvalue store for smal… 5
ubuntu/telegraf Telegraf collects, processes, aggregates & w… 4
ubuntu/zookeeper ZooKeeper maintains configuration informatio… 4
ubuntu/cortex Cortex provides storage for Prometheus. Long… 3
ubuntu/cassandra Cassandra, an open source NoSQL distributed … 2
bitnami/ubuntu-base-buildpack Ubuntu base compilation image 2 [OK]
ubuntu/loki Grafana Loki, a log aggregation system like … 0