Let's say I have old, unmaintained application that lives on a VPS (i.e. Symfony 3 PHP app that relies on PHP 5).
If some changes are needed I have to clone this app to my desktop, build it, change and re-deploy. As time goes, recreating desktop dev environment gets harder - in this example I can't simply build the app as I use PHP7 in my CLI that breaks building process.
I tried to dockerize the app, so I added Ubuntu 18 to my docker-compose file... and it doesn't work as latest Ubuntu that has PHP5 support is 14.04. 14.04 is also the oldest (official) version available on DockerHub. But will it be still available in 3 years? If not, Docker won't build a container.
So, my question is: is Docker a right tool to solve described problem at all?
If so, should I backup docker images described that my build relies on?
If not, beside proper maintenance, what tool is better?
You can install PHP5 in newer ubuntu versions, but it means adding an external repository.
You could also create your own docker image, containing only the libraries you want. If so, I'd advise to try and use alpine as a base image. There is a bit of a learning curve to adapt, but once you do it you'll have a small image tailored to your needs.
Given that containers allow you to isolate processus and conf with minimal footprint compared to a VM, I think it is the best option. Tailoring and maintaining your own image is not that expensive in terms of maintenance if you document it correctly, and it will allow you to always have a system 'maintaining' all your precise requirements.
Related
Our requirement is to create a container for legacy apps over docker.
We don't have the operating system support/application server support available, nor do we have knowledge to build them from scratch.
But we have a physical instance of the legacy app running in our farm.
We could get an ISO image from our server team if required, our question is if we get this ISO image can we export this as a docker image?
if yes, please let me know if there is any specific procedure or steps associated with it.
if no, please tell me why? and the possible workarounds for the same.
if we get this ISO image can we export this as a docker image?
I don't think there is an easy way (like push-the-export-button) to do this. Explanation follows...
You are describing a procedure taking place in the Virtual Machine world. You take a snapshot of a server, move the .iso file somewhere else and create a new VM that will run on a Hypervisor.
Containers are not VMs. They "contain" all the bytes that a service needs to run but not a whole operating system. They are supposed to run as processes on the host.
Workarounds:
You will have to get your hands dirty. This means that you will have to find out what the legacy app uses (for example Apache + PHP + MySql + app code) and build it from scratch with Docker.
Some thoughts:
containers are supposed to be lightweight. For example one might use one container for the database, another one for the Apache etc... Your case looks like you are moving towards a fat container that has everything inside.
Depending on what the legacy technology is, you might hit a wall... For example, if we are talking about something working with old php, mysql you might find ready-to-use images on hub.docker.com. But if the legacy app is a financial system written in cobol, I don't know what your starting point might be...
You will need to reverse engineer the application dependencies from the artifacts that you have in access to. This means recovering the language specific dependencies (whether python, java, php, node, etc). And any operating system level packages/dependencies that are required.
Essentially you are rebuilding the contents of that ISO image inside your docker file using OS package installation tools like apt, language level tools like pip, PECL, PEAR, composer, or maven, and finally the files that make up the app code.
So, for example: a PHP application might be dependent on having build-essential and php-mysql installed in the OS. Then the app may be dependent on packages like twig and monolog loaded through composer. If you are using SASS you may need to install ruby as well.
Your job is to track all these down and create a docker file that reproduces the iso image. If you are using a common stack like a J2EE app in tomcat, or a php app fronted by apache or ngnix, there will be base docker images that will get you most of the way to where you need to go.
It does look like there are some tools that can do this for you automatically: Dependency Walker equivalent for Linux?. I can't vouch for any of them. But you can also use command line tools. For example this will give you a list of all the user installed packages on a fedora system:
sudo dnf history userinstalled
When an app is using a dependency manager like composer or pip, there is usually a file that lists all the language specific dependencies.
At the end of the process you'll have a portable legacy app that can be easily deployed anywhere with a minimal footprint.
As one of the comments rightly points out, creating a VM from the ISO image is another way forward that will be much easier to accomplish. The application dependencies won't be explicit, but maybe that's ok for your use case.
There was a project thrown my way recently that involves the orchestration of several (Linux capable) embedded devices, deploying software to them, and allowing for the applications to be updated when the code base updates in a git repo.
The initial thought was to make a standard image for each device, and I set out, attempting to install docker on an UDOO Quad and an Intel Edison to start, but without any success up to this point.
My thinking is that it seems to be a good idea to install Docker on embedded devices--but if that's the case, surely it would have been ported by now. The only group out there that seems to be making these efforts is Resin.io.
Is there something I'm missing, or is there a clear reason why Docker doesn't make sense on embedded devices? If there isn't a reason, and it does make sense to run Docker on embedded systems, is there something I've overlooked out there: are there any sources of discussion on porting, or how-to's that cover this?
I have considered running docker on embedded devices (a mips system), but didn't go that way. There are some problems with it, in my humble view:
Docker is implemented in Golang. There is currently no available tool chain for mips to compile go. You will need to create the tool chain yourself using gcc-go.
The size of docker is larger than lxc. In a desktop computer this is not a problem, but the embedded device has limited flash storage.
Docker uses some quite up-to-date feature of linux kernel. Sometimes the kernel version on embedded devices are not so new and back-port is needed to make it work.
The docker image has to be built on the same architecture as the run time environment. It means that if you want to run a docker container on Raspberry Pi, the docker image has to be built on an ARM-architecture system. QEMU can be used to build docker image in the cloud, but it doesn't support all CPU architectures used in embedded system. (for example, it currently doesn't support MIPS)
In the end, lxc was chosen for the specific task of running a container on embedded device. It has limited features compared to docker, but currently it suits the requirement of the project.
As of year 2019, I would like to update this answer since I did port docker to embedded system with ARM cpu. With the price of flash usage, memory usage, by using docker you will have container management, image management, and many ready to run images from docker hub. So the decision is a balance between cost and features.
Here is an update for 2018:
You can work with Docker on embedded devices such as Raspberry Pi and Orange Pi quite easily now because of advancements in the development of Raspbian and Armbian operating system images. Specifically, both types of devices and their respective OS images now support kernels that are of sufficiently high enough versions to install Docker without any problems (at least version 3.10, though both now offer 4.x+ versions).
Your desire for faster rates of change can definitely be realized by using embedded Docker. I can say from experience that I have tested and regularly run the approach you describe. Basically, you start with a base operating system image such as Raspbian or Armbian, tweak that operating system enough that it's secure and has Docker installed, and then you use Docker for handling development iteration and application updates.
As an aside, if you are interested in running Docker on embedded Linux devices, then I recommend you check out a free, open-source, MIT-licensed command line tool I wrote to help developers work with embedded Docker on multiple devices at once: https://github.com/ForwardLoopLLC/floopcli .
Even if you are not interested in the tool itself, the documentation for the tool describes several patterns for working with Dockerized applications across multiple devices in multiple languages: https://docs.forward-loop.com/floopcli/master/index.html . The materials there should serve as a starting point for porting applications to Docker and then deploying them on embedded devices. The documentation also addresses some embedded device subtleties, such as differences between ARMv6 and ARMv7. Hopefully this helps you get started!
There is a great article on LinkedIn describing his experience with that
https://www.linkedin.com/pulse/whale-jar-when-running-docker-embedded-linux-good-thing-fletcher#pulse-comments-urn:li:article:7736487387895237975
Often embedded systems have a very slow rate of change. Docker works well on a minimum build then layering on top. If you want to sacrifice the overhead of running docker on a minimum embedded system for docker's ability to have a build system and steady rate of change then you could explorer it.
I currently have a LAMP stack installed on my mac running through Homebrew, which, to be honest hardly ever get's used.
Lately I have been working a lot with AngularJS and service based apps, so generally run the sites through a gulp / nodeJS based webserver.
I am totally frontend orientated, so very rarely do I play with backend related technologies other than the odd Drupal site and mysql.
I am interested to learn more NodeJS, perhaps even some Ruby, purely to understand programming more - not really for it to become my new job description.
So reading up on NodeJS a bit last night I read a lot about Docker, and installed it the toolkit and gui this morning. It looks pretty neat!
My question is: Would it work better for me to just run everything I need through Docker? For example, I can just install the mysql container, and turn it on when I need a db, and just spin up a drupal instance when I need one and connect it to my db instance?
I understand that running Docker on Mac is slower as it doesn't have the native Linux kernel and runs through a VM - but considering my needs from it, this should be okay?
I love the idea of just deploying containers, so will probably want to install Docker on my hosting environment too (VM in the cloud).
Follow up question: 90% of the sites I work on are AngularJS based frontends that speak to APIs that our backend guys build separately. Would it be overkill to have a Docker for each of those sites, or would I rather just run them all in one, or just bypass docker entirely for that (as I mentioned, I normally just load them up from within my Gulp's webserver)
Thanks a lot. I realise this is a n00b asking questions about big technology, but I'm trying to wrap my head around it and hopefully grow a bit in the process.
The interest in deploying Docker container is reproducibility.
You can easily reproduce:
either a complex development environment requiring the installation of numerous libraries (that you don't want to pollute directly your host)
or an execution environment, for a given tool to run (like a web server)
If you are not likely to repeat a setup (for dev or exec), a docker container would bring little value.
But if you want to keep track of the exact specification of an environment (through its Dockerfile) and will deploy it not just on your workstation, but in other places as well, then docker is certainly a good option to consider.
I would like to use the Spark-graphX packages available to Neo4j through Mazerunner, however I am an analyst and not a software person. I am running Windows 7 on my laptop and Neo4j 2.3.0, and would like a step-by-step guide explaining how I can set-up Mazerunner for both Community & Enterprise. There's a lot of mention of dockers and containers, and I have no idea what these are, or how to set them up. Simple instructions would be of sooo much help! :)
Docker is primarily Operating System Level Visualization technology designed to run on Unix based systems (Linux,Mac,FreeBSD). Luckily Docker provides a Windows version that sort of does the same thing on Unix.
What happens is, after you have installed Docker, it allows you to run what they call containers which are basically virtual machines on top of your host (Windows 7 Running Docker). This allows you to run services like Neo4j in an isolated environment. Docker also allows you to download and install pre-configured, pre-compiled images of operating systems that usually provide some sort of service or have some software pre-installed.
In your case, I believe all you have to do is:
First install Docker
Use "Docker Compose" to download and install the images.
Continue Reading the Tutorial as you have now installed the required docker images
Note: Some of the operations, like the one in Step 2 will require command-line access and Also the creation of a "docker-compose.yml" so, be sure to visit all the links I have provided. Spend a little time going through them and you should be alright.
PS: great blog. definitely bookmarking it!
my question is little vague but I tried looking for the answer here and there but could not understand if I can leverage docker for my work. My requirements
I usually try different versions of java, python and other software like different versions of eclipse, Linux package and other tools. This at the end make my Ubuntu installation a complete mess and some time completely broken. Then I started using Vm it solve most of the problem but make my pc very slow for frequent switching.
So my question can I achieve my work using docker without affecting my os? Can I run gui application, install different package without affecting underlying OS.
Switch actively between different docker container and underlying os.
Clean/remove unused/broken install of docker instance (containers?) etc. Any pointer to similar use case or how to would be helpful.
Thanks.
Ps- if it doesn't fit for SO then please move it to where it is best fitted. Sorry for non programming question.
Can it be done?
yes, there are examples of docker images that run graphical application, but running those containers might be a bit tricky. See for instance Can you run GUI apps in a docker container?
Is Docker the right tool for your problem ?
Maybe a package manager such as Nix would be better suited, as graphical software installed with it won't have any issue. With Nix you can install side-by-side many versions of a single software without interference.