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Many people are looking to take advantage of containers to isolate their workloads on a single system. Unlike traditional hypervisor-based virtualization, which utilizes the same operating system and packages, Containers allow you to segment off multiple applications with their own set of processes on the same instance.

Let’s walk through some grievances that many of us have faced at one time or another in our IT organizations:

Say, for example, your development team is setting up a web application. They want to set up a traditional 3 tier system with an app, database, and web servers. They notice there is a lot of support in the open source community for their app when it is run on Ubuntu Trusty (Ubuntu 14.04 LTS) and later. They’ve developed the app in their local sandbox with an Ubuntu image they downloaded, however, their company is a RedHat shop.

Now, depending on the type of environment you’re in, chances are you’ll have to wait for the admins to provision an environment for you. This often entails (but is not limited to) spinning up an instance, reviewing the most stable version of the OS, creating a new hardened AMI, adding it to Packer, figuring out which configs to manage, and refactoring provisioning scripts to utilize aptitude and Ubuntu’s directory structure (e.g Debian has over 50K packages to choose from and manage). In addition to that, the most stable version of Ubuntu is missing some newer packages that you’ve tested in your sandbox that need to be pulled from source or another repository. At this point, the developers are procuring configuration runbooks to support the app while the admin gets up to speed with the OS (not significant but time-consuming nonetheless).

You can see my point here. A significant amount of overhead has been introduced, and it’s stagnating development. And think about the poor sysadmins. They have other environments that they need to secure, networking spaces to manage, operations to improve, and existing production stacks they have to monitor and support while getting bogged down supporting this app that is still in the very early stages of development. This could mean that mission-critical apps are potentially losing visibility and application modernization is stagnating. Nobody wins in this scenario.

Now let us revisit the same scenario with containers:

I was able to run my Jenkins build server and an NGINX web proxy, both running on a hardened CentOS7 AMI provided by the Systems Engineers with docker installed.  From there I executed a docker pull  command pointed at our local repository and deployed two docker images with Debian as the underlying OS.

$ docker pull my.docker-repo.com:4443/jenkins
$ docker pull my.docker-repo.com:4443/nginx

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

$ docker ps

7478020aef37 my.docker-repo.com:4443/jenkins/jenkins:lts   “/sbin/tini — /us …”  16 minutes ago   Up 16 minutes ago  8080/tcp, 0.0.0.0:80->80/tcp, 50000/tcp jenkins

d68e3b96071e my.docker-repo.com:4443/nginx/nginx:lts “nginx -g ‘daemon of…” 16 minutes ago Up 16 minutes 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp nginx

$ sudo systemctl status jenkins-docker

jenkins-docker.service – Jenkins
Loaded: loaded (/etc/systemd/system/jenkins-docker.service; enabled; vendor preset: disabled)
Active: active (running) since Thu 2018-11-08 17:38:06 UTC; 18min ago
Process: 2006 ExecStop=/usr/local/bin/jenkins-docker stop (code=exited, status=0/SUCCESS)

The processes above were executed on the actual instance. Note how I’m able to execute a cat of the OS release file from within the container

sudo docker exec d68e3b96071e cat /etc/os-release
PRETTY_NAME=”Debian GNU/Linux 9 (stretch)”
NAME=”Debian GNU/Linux”
VERSION_ID=”9″
VERSION=”9 (stretch)”
ID=debian
HOME_URL=”https://www.debian.org/
SUPPORT_URL=”https://www.debian.org/support
BUG_REPORT_URL=”https://bugs.debian.org/

I was able to do so because Docker containers do not have their own kernel, but rather share the kernel of the underlying host via linux system calls (e.g setuid, stat, umount, ls) like any other application. These system calls (or syscalls for short) are standard across kernels, and Docker supports version 3.10 and higher. In the event older syscalls are deprecated and replaced with new ones, you can update the kernel of the underlying host, which can be done independently of an OS upgrade. As far as containers go, the binaries and aptitude management tools are the same as if you installed Ubuntu on an EC2 instance (or VM).

Q: But I’m running a windows environment. Those OS’s don’t have a kernel. 

Yes, developers may want to remove cost overhead associated with Windows licenses by exploring running their apps on Linux OS. Others may simply want to modernize their .NET applications by testing out the latest versions on Containers. Docker allows you to run Linux VM’s on Windows 10 and Server 2016. As docker was written to initially execute on Linux distributions, in order to take advantage of multitenant hosting, you will have to run Hyper-V containers, which provision a thin VM on top of your hosts. You can then manage your mixed environment of Windows and Linux hosts via the –isolate option. More information can be found in the Microsoft and Docker documentation.

Conclusion:

IT teams need to be able to help drive the business forward. Newer technologies and security patches are procured on a daily basis. Developers need to be able to freely work on modernizing their code and applications. Concurrently, Operations needs to be able to support and enhance the pipelines and platforms that get the code out faster and securely. Leveraging Docker containers in conjunction with these pipelines further helps to ensure these are both occurring in parallel without the unnecessary overhead. This allows teams to work independently in the early stages of the development cycle and yet more collaboratively to get the releases out the door.

For help getting started leveraging your environment to take advantage of containerization, contact us.

-Sabine Blair, Systems Engineer & Cloud Consultant

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