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Ahmer's SysAdmin Recipes is a blog for Linux System Administrators. This blog provides recipes for Installation & Configuration of Linux, Ubuntu, Oracle Database, MySQL, Apache, Nginx, Oracle Cloud Control, FreeIPA, Kerberos & OpenLDAP, Subversion, PXE, DevOps, etc. over Red Hat Enterprise Linux (RHEL), CentOS, Ubuntu and Windows.

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Saturday, 6 April 2019

Configure Secure Registry with Docker-Distribution on CentOS 7

Configure Secure Registry with Docker-Distribution on CentOS 7

Docker Registry is a content storage and delivery system, that stores different tagged versions of Docker images. Users interact with Docker Registry by means of a Push or Pull methods. Docker Hub is a public docker registry that provides millions of images to trillions of users. But there are scenarios, where we are required to setup a private and secure in-premises Docker Registry.

We have already configured a Private Docker Registry on CentOS 7 in our previous article using Docker technology, where we have created a Docker Registry container using Docker Engine CE.

Now, we are using an alternate method to create a Secure Docker Registry without using containers technology. In this article, we will configure a Secure Registry with Docker-Distribution on CentOS 7 and then test it by using it through Docker hosts.

It is highly recommended that you should read Docker Deep Dive for some basic to advance level understanding of Docker technology. It will also help you to better understand this article.

 

System Specification:

We have configured a CentOS 7 virtual machine with following specification.

Hostname: docker-distribution-01.example.com
IP Address: 192.168.116.153/24
Operating System: CentOS 7.6
CPU: 3.4 Ghz (1 Core)
Memory: 1 GB
Storage: 40 GB

We are also using a Docker Host with following specification to test our Secure Docker Registry.

Hostname: docker-manager-01.example.com
IP Address: 192.168.116.150/24
Operating System: CentOS 7.6
Docker Version: Docker Engine CE 18.09

 

Installing Docker-Distribution on CentOS 7:

Connect with docker-distribution-01.example.com using ssh as root user.

Docker-Distribution package is available in extras yum repository.

Check the available version of Docker-Distribution package.

[root@docker-distribution-01 ~]# yum info docker-distribution Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: mirrors.ges.net.pk * extras: mirrors.ges.net.pk * updates: mirror1.ku.ac.th Installed Packages Name : docker-distribution Arch : x86_64 Version : 2.6.2 Release : 2.git48294d9.el7 Size : 12 M Repo : installed From repo : extras Summary : Docker toolset to pack, ship, store, and deliver content URL : https://github.com/docker/distribution License : ASL 2.0 Description : Docker toolset to pack, ship, store, and deliver content

Install Docker-Distribution package as follows.

[root@docker-distribution-01 ~]# yum install -y docker-distribution Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: ftp.iitm.ac.in * extras: mirrors.ges.net.pk * updates: mirror2.totbb.net Resolving Dependencies --> Running transaction check ---> Package docker-distribution.x86_64 0:2.6.2-2.git48294d9.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: docker-distribution x86_64 2.6.2-2.git48294d9.el7 extras 3.5 M Transaction Summary ================================================================================ Install 1 Package Total download size: 3.5 M Installed size: 12 M Downloading packages: docker-distribution-2.6.2-2.git48294d9.el7.x86_64.rpm | 3.5 MB 00:08 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : docker-distribution-2.6.2-2.git48294d9.el7.x86_64 1/1 Verifying : docker-distribution-2.6.2-2.git48294d9.el7.x86_64 1/1 Installed: docker-distribution.x86_64 0:2.6.2-2.git48294d9.el7 Complete!

Docker-Distribution package has been installed on CentOS 7.

 

Configuring Secure Registry with Docker-Distribution:

We are configuring a Secure Docker Registry, therefore, we have to create a SSL/TLS certificate for our Docker Registry Service.

[root@docker-distribution-01 ~]# openssl req \ > -newkey rsa:2048 \ > -nodes -sha256 \ > -x509 -days 365 \ > -keyout /etc/pki/tls/private/registry.key \ > -out /etc/pki/tls/registry.crt Generating a 2048 bit RSA private key ..............+++ .............................................................+++ writing new private key to '/etc/pki/tls/private/registry.key' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [XX]:PK State or Province Name (full name) []:Sindh Locality Name (eg, city) [Default City]:Karachi Organization Name (eg, company) [Default Company Ltd]:Ahmer's SysAdmin Recipes Organizational Unit Name (eg, section) []:ITLAB Common Name (eg, your name or your server's hostname) []:docker-distribution-01.example.com Email Address []:root@docker-distribution-01.example.com

To restrict anonymous access, we will setup basic HTTP authentication for our Docker Registry Service. For this purpose, we need to install htpasswd utility to create a HTTP password file.

[root@docker-distribution-01 ~]# yum install -y httpd-tools Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: ftp.iitm.ac.in * extras: mirror.nbrc.ac.in * updates: mirror.nbrc.ac.in Resolving Dependencies --> Running transaction check ---> Package httpd-tools.x86_64 0:2.4.6-88.el7.centos will be installed --> Processing Dependency: libaprutil-1.so.0()(64bit) for package: httpd-tools-2.4.6-88.el7.centos.x86_64 --> Processing Dependency: libapr-1.so.0()(64bit) for package: httpd-tools-2.4.6-88.el7.centos.x86_64 --> Running transaction check ---> Package apr.x86_64 0:1.4.8-3.el7_4.1 will be installed ---> Package apr-util.x86_64 0:1.5.2-6.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: httpd-tools x86_64 2.4.6-88.el7.centos base 90 k Installing for dependencies: apr x86_64 1.4.8-3.el7_4.1 base 103 k apr-util x86_64 1.5.2-6.el7 base 92 k Transaction Summary ================================================================================ Install 1 Package (+2 Dependent packages) Total download size: 286 k Installed size: 584 k Downloading packages: (1/3): apr-1.4.8-3.el7_4.1.x86_64.rpm | 103 kB 00:03 (2/3): httpd-tools-2.4.6-88.el7.centos.x86_64.rpm | 90 kB 00:03 (3/3): apr-util-1.5.2-6.el7.x86_64.rpm | 92 kB 00:04 -------------------------------------------------------------------------------- Total 69 kB/s | 286 kB 00:04 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : apr-1.4.8-3.el7_4.1.x86_64 1/3 Installing : apr-util-1.5.2-6.el7.x86_64 2/3 Installing : httpd-tools-2.4.6-88.el7.centos.x86_64 3/3 Verifying : httpd-tools-2.4.6-88.el7.centos.x86_64 1/3 Verifying : apr-util-1.5.2-6.el7.x86_64 2/3 Verifying : apr-1.4.8-3.el7_4.1.x86_64 3/3 Installed: httpd-tools.x86_64 0:2.4.6-88.el7.centos Dependency Installed: apr.x86_64 0:1.4.8-3.el7_4.1 apr-util.x86_64 0:1.5.2-6.el7 Complete!

Now, create a HTTP password file as follows:

[root@docker-distribution-01 ~]# htpasswd -c -B /etc/docker-distribution/dockerpasswd ahmer New password: Re-type new password: Adding password for user ahmer

We have used –B switch above to create an entry with bcrypt encryption because it is the only supported format right now, and the entries with other hash types will be ignored.

Edit Docker Registry configuration file.

[root@docker-distribution-01 ~]# vi /etc/docker-distribution/registry/config.yml

and update it as follows:

version: 0.1 log: fields: service: registry storage: cache: layerinfo: inmemory filesystem: rootdirectory: /var/lib/registry http: addr: 192.168.116.153:5000 tls: certificate: /etc/pki/tls/registry.crt key: /etc/pki/tls/private/registry.key auth: htpasswd: realm: example.com path: /etc/docker-distribution/dockerpasswd

Warning: Avoid use of TAB key for indention of lines. Otherwise, the docker-distribution service will give you following error during startup.

configuration error: error parsing /etc/docker-distribution/registry/config.yml: yaml: line 12: found character that cannot start any token

Please refer to Docker Documentation for more configuration options in config.yml.

Start and Enable docker-distribution service.

[root@docker-distribution-01 ~]# systemctl start docker-distribution [root@docker-distribution-01 ~]# systemctl enable docker-distribution Created symlink from /etc/systemd/system/multi-user.target.wants/docker-distribution.service to /usr/lib/systemd/system/docker-distribution.service.

Allow Docker Registry service port 5000/tcp in Linux Firewall.

[root@docker-distribution-01 ~]# firewall-cmd --permanent --add-port=5000/tcp success [root@docker-distribution-01 ~]# firewall-cmd --reload success

Our Secure Docker Registry has been configured.

 

Use Secured Docker Registry on Docker Hosts:

Connect with Docker Host docker-manager-01.example.com using ssh as root user.

Add an entry in Local DNS Resolver to setup name resolution of our Secured Registry Server.

[root@docker-manager-01 ~]# cat >> /etc/hosts << EOF > 192.168.116.153 docker-distribution-01.example.com docker-distribution-01 > EOF

Install Docker Registry Service TLS/SSL certificate on Docker Host.

[root@docker-manager-01 ~]# mkdir -p /etc/docker/certs.d/docker-distribution-01.example.com:5000 [root@docker-manager-01 ~]# scp root@docker-distribution-01:/etc/pki/tls/registry.crt /etc/docker/certs.d/docker-distribution-01.example.com\:5000/ root@docker-distribution-01's password: registry.crt

Pull an image from Docker Hub. We will later push this image to our Secured Docker Registry.

[root@docker-manager-01 ~]# docker pull alpine Using default tag: latest latest: Pulling from library/alpine 8e402f1a9c57: Pull complete Digest: sha256:644fcb1a676b5165371437feaa922943aaf7afcfa8bfee4472f6860aad1ef2a0 Status: Downloaded newer image for alpine:latest

Tag alpine image before pushing it to Secure Docker Registry.

[root@docker-manager-01 ~]# docker tag alpine docker-distribution-01.example.com:5000/alpine

Login to Secured Docker Registry.

[root@docker-manager-01 ~]# docker login docker-distribution-01.example.com:5000 Username: ahmer Password: WARNING! Your password will be stored unencrypted in /root/.docker/config.json. Configure a credential helper to remove this warning. See https://docs.docker.com/engine/reference/commandline/login/#credentials-store Login Succeeded

Push alpine image to our Secured Docker Registry.

[root@docker-manager-01 ~]# docker push docker-distribution-01.example.com:5000/alpine The push refers to repository [docker-distribution-01.example.com:5000/alpine] bcf2f368fe23: Pushed latest: digest: sha256:d05ecd4520cab5d9e5d877595fb0532aadcd6c90f4bbc837bc11679f704c4c82 size: 528

We have Successfully configured a Secure Registry with Docker-Distribution on CentOS 7.

Configure Secure Registry with Docker-Distribution on CentOS 7


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