both docker search can be found, of course, provided that you can connect to the Internet,
or access it directly with a browser, as shown below.
https://index.docker.io/v1/search?q=rhel7.2&n=25:
{"num_pages":1,"num_results":12,"page_size":25,"page":1,"query":"rhel7.2","results":[{"name":"caiqian/rhel7.2beta-overlay","description":"RHEL7.2 Beta image for overlayfs testing","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"vtas/rhel7.2","description":"","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"mcalizo/rhel7.2systemd","description":"RHEL7.2 with Systemd","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"shrutikag/rhel7.2","description":"","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"adriaanbrae/rhel7.2","description":"","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"aramatra/rhel7.2","description":"","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"deepfenceio/rhel7.2","description":"","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"mmithaiw/rhel7.2-modified","description":"","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"jahndai/rhel7","description":"Clean image for FET user. By RHEL7.2","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"mbafna/rhel72-lvm2","description":"RHEL7.2 image with LVM2 ","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"vgs24/rhel72le","description":"Created a rhel7.2 le docker image","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"mkimranbasha/rhel72","description":"Docker file for RHEL7.2","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false}]}
https://index.docker.io/v1/search?q=centos7&n=25:
{"num_pages":217,"num_results":5407,"page_size":25,"page":1,"query":"centos7","results":[{"name":"openshift/base-centos7","description":"A Centos7 derived base image for Source-To-Image builders","star_count":22,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/jenkins-2-centos7","description":"A Centos7 based Jenkins v2.x image for use with OpenShift v3","star_count":12,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"ansible/centos7-ansible","description":"Ansible on Centos7","star_count":109,"is_trusted":true,"is_automated":true,"is_official":false},{"name":"openshift/mysql-55-centos7","description":"DEPRECATED: A Centos7 based MySQL v5.5 image for use with OpenShift v3","star_count":6,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/jenkins-1-centos7","description":"DEPRECATED: A Centos7 based Jenkins v1.x image for use with OpenShift v3","star_count":4,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/wildfly-101-centos7","description":"A Centos7 based WildFly v10.1 image for use with OpenShift v3","star_count":3,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/wildfly-100-centos7","description":"A Centos7 based WildFly v10.0 image for use with OpenShift v3","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/php-55-centos7","description":"DEPRECATED: A Centos7 based PHP v5.5 image for use with OpenShift v3","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/wildfly-81-centos7","description":"A Centos7 based WildFly v8.1 image for use with OpenShift v3","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/wildfly-90-centos7","description":"A Centos7 based WildFly v9.0 image for use with OpenShift v3","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/nodejs-010-centos7","description":"DEPRECATED: A Centos7 based NodeJS v0.10 image for use with OpenShift v3","star_count":4,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/mongodb-24-centos7","description":"DEPRECATED: A Centos7 based MongoDB v2.4 image for use with OpenShift v3","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/ruby-20-centos7","description":"DEPRECATED: A Centos7 based Ruby v2.0 image for use with OpenShift v3","star_count":3,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/postgresql-92-centos7","description":"DEPRECATED: A Centos7 based PostgreSQL v9.2 image for use with OpenShift v3","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/python-33-centos7","description":"DEPRECATED: A Centos7 based Python v3.3 image for use with OpenShift v3","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/perl-516-centos7","description":"DEPRECATED: A Centos7 based Perl v5.16 image for use with OpenShift v3","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"fortinj66/centos7-s2i-nodejs","description":"based off of ryanj/centos7-s2i-nodejs. Biggest change is to allow a build script be be run","star_count":0,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/wildfly-110-centos7","description":"A Centos7 based WildFly v11.0 image for use with OpenShift v3","star_count":1,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/python-35-centos7","description":"Platform for building and running Python 3.5 applications\n","star_count":20,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/postgresql-96-centos7","description":"PostgreSQL is an advanced Object-Relational database management system\n","star_count":16,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/mysql-57-centos7","description":"MySQL 5.7 SQL database server\n","star_count":27,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/httpd-24-centos7","description":"Platform for running Apache httpd 2.4 or building httpd-based application\n","star_count":12,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"openshift/php-56-centos7","description":"DEPRECATED: A Centos7 based PHP v5.6 image for use with OpenShift v3","star_count":2,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/php-56-centos7","description":"Platform for building and running PHP 5.6 applications\n","star_count":12,"is_trusted":false,"is_automated":false,"is_official":false},{"name":"centos/php-70-centos7","description":"Platform for building and running PHP 7.0 applications\n","star_count":9,"is_trusted":false,"is_automated":false,"is_official":false}]}
choose the docker pull you want from the above, export it with docker export and install it at Gueqi.