Starting and managing Docker containers
by Uday R. Sawant, William Leemans, Jonathan Hobson, Oliver Pelz
Linux: Powerful Server Administration
- Linux: Powerful Server Administration
- Table of Contents
- Linux: Powerful Server Administration
- Linux: Powerful Server Administration
- Credits
- Preface
- 1. Module 1
- 1. Managing Users and Groups
- 2. Networking
- Introduction
- Connecting to a network with a static IP
- Installing the DHCP server
- Installing the DNS server
- Hiding behind the proxy with squid
- Being on time with NTP
- Discussing load balancing with HAProxy
- Tuning the TCP stack
- Troubleshooting network connectivity
- Securing remote access with OpenVPN
- Securing a network with uncomplicated firewall
- Securing against brute force attacks
- Discussing Ubuntu security best practices
- 3. Working with Web Servers
- Introduction
- Installing and configuring the Apache web server
- Serving dynamic contents with PHP
- Hosting multiple websites with a virtual domain
- Securing web traffic with HTTPS
- Installing Nginx with PHP_FPM
- Setting Nginx as a reverse proxy
- Load balancing with Nginx
- Setting HTTPs on Nginx
- Benchmarking and performance tuning of Apache
- Securing the web server
- Troubleshooting the web server
- 4. Working with Mail Servers
- 5. Handling Databases
- Introduction
- Installing relational databases with MySQL
- Storing and retrieving data with MySQL
- Importing and exporting bulk data
- Adding users and assigning access rights
- Installing web access for MySQL
- Setting backups
- Optimizing MySQL performance – queries
- Optimizing MySQL performance – configuration
- Creating MySQL replicas for scaling and high availability
- Troubleshooting MySQL
- Installing MongoDB
- Storing and retrieving data with MongoDB
- 6. Network Storage
- 7. Cloud Computing
- 8. Working with Containers
- Introduction
- Installing LXD, the Linux container daemon
- Deploying your first container with LXD
- Managing LXD containers
- Managing LXD containers – advanced options
- Setting resource limits on LXD containers
- Networking with LXD
- Installing Docker
- Starting and managing Docker containers
- Creating images with a Dockerfile
- Understanding Docker volumes
- Deploying WordPress using a Docker network
- Monitoring Docker containers
- Securing Docker containers
- 9. Streaming with Ampache
- 10. Communication Server with XMPP
- 11. Git Hosting
- Introduction
- Installing Git
- Creating a local repository with Git CLI
- Storing file revisions with Git commit
- Synchronizing the repository with a remote server
- Receiving updates with Git pull
- Creating repository clones
- Installing GitLab, your own Git hosting
- Adding users to the GitLab server
- Creating a repository with GitLab
- Automating common tasks with Git hooks
- 12. Collaboration Tools
- 13. Performance Monitoring
- 14. Centralized Authentication Service
- 2. Module 2
- 1. Installing CentOS
- Introduction
- Downloading CentOS and confirming the checksum on Windows or OS X
- Creating USB installation media on Windows or OS X
- Performing an installation of CentOS using the graphical installer
- Running a netinstall over HTTP
- Installing CentOS 7 using a kickstart file
- Getting started and customising the boot loader
- Troubleshooting the system in rescue mode
- Updating the installation and enhancing the minimal install with additional administration and development tools
- 2. Configuring the System
- Introduction
- Navigating text files with less
- Introduction to Vim
- Speaking the right language
- Synchronizing the system clock with NTP and the chrony suite
- Setting your hostname and resolving the network
- Building a static network connection
- Becoming a superuser
- Customizing your system banners and messages
- Priming the kernel
- 3. Managing the System
- Introduction
- Knowing and managing your background services
- Troubleshooting background services
- Tracking system resources with journald
- Configuring journald to make it persistent
- Managing users and their groups
- Scheduling tasks with cron
- Synchronizing files and doing more with rsync
- Maintaining backups and taking snapshots
- Monitoring important server infrastructure
- Taking control with GIT and Subversion
- 4. Managing Packages with YUM
- 5. Administering the Filesystem
- 6. Providing Security
- 7. Building a Network
- 8. Working with FTP
- 9. Working with Domains
- 10. Working with Databases
- 11. Providing Mail Services
- 12. Providing Web Services
- 13. Operating System-Level Virtualization
- 14. Working with SELinux
- 15. Monitoring IT Infrastructure
- 1. Installing CentOS
- 3. Module 3
- 1. Working with KVM Guests
- 2. Deploying RHEL "En Masse"
- 3. Configuring Your Network
- 4. Configuring Your New System
- 5. Using SELinux
- 6. Orchestrating with Ansible
- 7. Puppet Configuration Management
- 8. Yum and Repositories
- 9. Securing RHEL 7
- 10. Monitoring and Performance Tuning
- Bibliography
- Index
So, we have installed the latest Docker binary. In this recipe, we will start a new container with Docker. We will see some basic Docker commands to start and manage Docker containers.
Make sure that you have installed Docker and set your user as a member of the Docker group.
You may need sudo privileges for some commands.
Let's create a new Docker container and start it. With Docker, you can quickly start a container with the docker run command:
- Start a new Docker container with the following command:
$ docker run -it --name dc1 ubuntu /bin/bash Unable to find image 'ubuntu:trusty' locally trusty: Pulling from library/ubuntu 6599cadaf950: Pull complete 23eda618d451: Pull complete ... Status: Downloaded newer image for ubuntu:trusty root@bd8c99397e52:/#
Once a container has been started, it will drop you in a new shell running inside it. From here, you can execute limited Ubuntu or general Linux commands, which will be executed inside the container.
- When you are done with the container, you can exit from the shell by typing
exitor pressing Ctrl + D. This will terminate your shell and stop the container as well. - Use the
docker pscommand to list all the containers and check the status of your last container:$ docker ps -a
By default,
docker pslists all running containers. As our container is no longer running, we need to use the-aflag to list all available containers. - To start the container again, you can use the
docker startcommand. You can use the container name or ID to specify the container to be started:$ docker start -ia dc1
The
-iflag will start the container in interactive mode and the-aflag will attach to a terminal inside the container. To start a container in detached mode, use thestartcommand without any flags. This will start the container in the background and return to the host shell:$ docker start dc1 - You can open a terminal inside a detached container with
docker attach:$ docker attach dc1 - Now, to detach a terminal and keep the container running, you need the key combinations Ctrl + P and Ctrl + Q. Alternatively, you can type
exitor press Ctrl + C to exit the terminal and stop the container. - To get all the details of a container, use the
docker inspectcommand with the name or ID of the container:$ docker inspect dc1 | lessThis command will list all the details of the container, including container status, network status and address, and container configuration files.
- To execute a command inside a container, use
docker exec. For example, the following command gets the environment variables from thedc1container:$ docker exec dc1 envThis one gets the IP address of a container:
$ docker exec dc1 ifconfig
- To get the processes running inside a container, use the
docker topcommand:$ docker top dc1
- Finally, to stop the container, use
docker stop, which will gracefully stop the container after stopping processes running inside it:$ docker stop dc1 - When you no longer need the container, you can use
docker rmto remove/delete it:$ docker rm dc1
We started our first Docker container with the docker run command. With this command, we instructed the Docker daemon to start a new container with an image called Ubuntu, start an interactive session (-i), and allocate a terminal (-t). We also elected to name our container with the --name flag and execute the /bin/bash command inside a container once it started.
The Docker daemon will search for Ubuntu images in the local cache or download the image from Docker Hub if the specified image is not available in the local cache. Docker Hub is a central Docker image repository. It will take some time to download and extract all the layers of the images. Docker maintains container images in the form of multiple layers. These layers can be shared across multiple container images. For example, if you have Ubuntu running on a server and you need to download the Apache container based on Ubuntu, Docker will only download the additional layer for Apache as it already has Ubuntu in the local cache, which can be reused.
Docker provides various other commands to manage containers and images. We have already used a few of them in the previous example. You can get the full list of all available commands from the command prompt itself, by typing docker followed by the
Enter key. All commands are listed with their basic descriptions. To get more details on any specific subcommand, use its help menu, as follows:
$ docker rmi --help
Docker images can be used to quickly create runc containers, as follows:
$ sudo apt-get install runc $ mkdir -p runc/rootfs && cd runc $ docker run --name alpine alpine sh $ docker export alpine > alpine.tar $ tar -xf alpine.tar -C rootfs $ runc spec $ sudo runc start alpine
- Docker run documentation: http://docs.docker.com/engine/reference/commandline/run/
- Check manual entries for any Docker command:
$ man docker create
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