Docker

Installing Docker and Docker Distribution

Install the docker and Docker Distribution packages. These packages are found in the Extras repo.

yum install -y docker docker-distribution

Enable and start Docker and Docker Distribution.

systemctl enable docker

systemctl enable docker-distribution

systemctl start docker

systemctl start docker-distribution

Docker Registry

Configuration

STORAGE

To change the location of the stored docker images amend the rootdirectory config setting in /etc/docker-distribution/registry/config.yml.

vim /etc/docker-distribution/registry/config.yml

rootdirectory: /var/lib/registry

HTTPS/TLS

Create a self signed certificate or purchase a certificate from a trusted CA.

mkdir /certs/

cd /certs/

openssl req -newkey rsa:4096 -nodes -sha256 -keyout server.key -x509 -days 365 -out server.crt

Copy the keys into /etc/docker/certs.d/

cp server.crt server.key /etc/docker/certs.d/.

Edit the registry configuration file and add the following under http.

vim /etc/docker-distribution/registry/config.yml

http:

    addr: 192.168.0.1:5000

    tls:

      certificate: /etc/docker/certs.d/server.crt

      key: /etc/docker/certs.d/server.key

Auhentication

There are several methods for authentication but we will use a htpasswd file.

Install httpd-tools

yum install  httpd-tools

Create the htpasswd file

mkdir /etc/docker-distribution/registry/auth

chmod 750 /etc/docker-distribution/registry/auth

htpasswd -Bc /etc/docker-distribution/registry/auth/registery_users user_name

Edit the registry configuration file and add the following under Auth.

vim /etc/docker-distribution/registry/config.yml

auth:

  htpasswd:

    realm: basic-realm

    path: /etc/docker-distribution/registry/auth/registery_users

Using the Docker Registry

Pull an image from a remote registry.

docker pull registry.access.redhat.com/rhel7/rhel

List images in Docker

docker images

Load a tarball image into Docker

docker load -i rhel-server-docker-7.2.x86_64.tar.gz

To push an image into your local repository you need to tag it with your registry information first.

docker tag bef54b8f8a2f localhost:5000/docker_image

docker push localhost:5000/docker_image

Running Docker Containers

Run a quick command

docker run -v /usr/sbin:/usr/bin --rm rhel /usr/sbin/ip addr show eth0

# -v Mount host directory to make it available to the container

# --rm Remove the container after execution of the command

docker run -v /usr/sbin:/usr/sbin --name=myipaddr rhel /usr/sbin/ip addr show eth0

# --name Names the container so it can be started again by name next time.

docker start -i myipaddr

# -i Attach container's STDIN

View the docker file in the container

docker run --rm localhost:5000/rhel7 ls /root/buildinfo

Run a shell inside the container. From here you can use yum and other commands

docker run --name=mybash -it rhel /bin/bash

Show containers

docker ps -a

Bind mount log files. This makes the containers messages available to the host

docker run --rm --name=test_log3 -v /dev/log:/dev/log server2.grow4.co.uk:5000/rhel7 logger "Testing logging to the host"

List containers

docker ps # Runninig containers

docker ps -a # All containers

Inspect the metadata of an existing container

docker inspect

docker inspect --format='{{.NetworkSettings.Networks.bridge.IPPrefixLen}}' 8bfde4062140

Investigating within a running Docker container

docker exec will run a command in a container without interrupting the application the container is running.

docker exec -it myrhel_httpd /bin/bash

If you ran a container, but didn’t remove it (--rm), that container is stored on your local system and ready to run again. To start a previously run container that wasn’t removed, use the start option. To stop a running container, use the stop option

Start a non-interactive user

docker start container_name

Start an interactive container

docker start -a -i container_name

# -a attache

# -i interactive

Stopping containers

docker stop container_name

docker kill --signul="SIGHUP"

Removing containers

docker rm container_name

docker rm container_name1 container_name2

# Remove all containers

docker rm $(docker ps -aq)

Creating Docker Images

Create Docker Images