Questions tagged [containers]

Use for generic questions on containers that do not fall under a specific container technology, like Docker, LXC, FreeBSD Jails, OpenBSD sysjails, Solaris Containers, WPARs, etc. Also use where the specific technology is not relevant to the question.

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139 votes
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Why it is recommended to run only one process in a container?

In many blog posts, and general opinion, there is a saying that goes "one process per container". Why does this rule exist? Why not run ntp, nginx, uwsgi and more processes in a single container that ...
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46 votes
3 answers
13k views

What are the reasons Docker should not be used for databases?

I'm having a discussion with a friend about use cases for Docker. One guy in the team wants to use Docker for everything - like a kind of universal unix process wrapper. The other thinks that Docker ...
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26 votes
4 answers
2k views

What is a container?

There are some questions about containers, such as: What role do Configuration Managment tools play in immutable infrastructure? Which problems does a container orchestration solve? Simple CI/CD ...
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22 votes
3 answers
18k views

Difference between chroot and Docker

I don't understand the difference between docker and chroot. Yes its nice in terms of the packaging the registry. But somehow I get the feeling its just chroot with extra bells and whistles. I know I'...
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20 votes
2 answers
5k views

Where should I put my application configuration?

I've been reading lately a debate about "Where should properties that depend on the environment be stored?". The classical way is to have multiple property files, one by environment, and based on an ...
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  • 301
15 votes
3 answers
1k views

Simple CI/CD Containers in AWS

I am using AWS Code Pipeline, Code Build to create a new Docker container and push it to ECR. My application is a simple straight-forward single-container based. What would be less friction approach ...
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15 votes
3 answers
8k views

On Azure, how do I run a short-lived Docker container on a schedule?

I have a fairly simple Unix shell script packaged up in an Alpine Linux Docker container hosted on an Azure container registry. A VM runs this script with cron: docker login <snip> docker pull ...
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14 votes
2 answers
567 views

Combine Docker Swarm and Kubernetes

My company is trying to play a little catch-up in the DevOps space. I have been doing a lot of research on containerization of applications and the orchestration systems that go with it. I came across ...
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14 votes
1 answer
812 views

Which problems does a container orchestration solve?

Every company who has anything to do with containers these days, including public cloud providers, is creating their own solution for container orchestration. These include: Kubernetes Docker Swarm ...
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13 votes
2 answers
672 views

What role do Configuration Managment tools play in immutable infrastructure?

If I'm using immutable servers/containers, do I need tools like Chef, Puppet, Ansible, or Salt? Those config management tools are designed to establish a configuration and then maintain it. If I'm ...
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13 votes
2 answers
10k views

Does Docker allow containers to be OS agnostic?

We currently use a Windows based server to host 2 VMs. One VM uses Windows with a Windows app and the other VM uses Linux with a Linux app. Is the below scenario possible? Bare server with Windows ...
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  • 231
13 votes
2 answers
3k views

How to investigate a main process that has died in a docker container?

Sometimes you have to investigate a container, which is stopped, or a container which after starting up dies very quickly and stops. docker exec -ti <id> bash only works on running containers, ...
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  • 1,557
13 votes
2 answers
1k views

Docker Container capacity planning

I'm running my application on 4 Virtual Machines with 8 3.2 GHz Virtual CPUs and 32 GB, however, I will be splitting up the processes into separate containers. I am not sure how many containers to ...
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  • 139
9 votes
1 answer
2k views

Does "docker run" actually SSH into the container?

If I run docker run -it ubuntu bash Does it actually SSH into the container, or does it use another protocol?
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8 votes
1 answer
672 views

Should worker processes of web applications be placed in separate containers?

My setup is based on a Flask app that has a PostgreSQL and Redis database. In addition, a worker process is started to handle asynchronous tasks such as sending emails. I use Gunicorn to create ...
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7 votes
5 answers
287 views

What are best practices and/or tools for updating AMIs on a regular basis?

I have a Master-Workers style computation model. And, I launch the workers via an AMI through an Ansible playbook. The workers' AMI has all the necessary configs needed for doing the computation (...
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  • 2,756
7 votes
2 answers
4k views

Stress testing for docker container

I want my container to die under high pressure to check monitoring and alerting as well as compose autorestarts. What is best way to simulate heavy load within docker container. I've tried so far ...
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7 votes
1 answer
288 views

How do you monitor and alert on thrashing containers?

Are there any proposed best practices for how to monitor for thrashing containers? We're in a situation where we have containers that might try to come up and will crash -> restart a few dozen times ...
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  • 295
6 votes
1 answer
475 views

Does the "cattle not pets" distinction apply as equally to machine instances as to containers?

There is a great discussion of the Cattle vs Pets distinction from Randy Bias here. Martin Fowler talks about a SnowFlakeServer. In a series of talks, Adrian Cockcroft talks about how they moved ...
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  • 1,083
6 votes
1 answer
3k views

What's the relationship between ContainerD and Docker?

I'm aware that Kubernetes uses containerd internally and that containerd is part of Docker. Does that mean that Kubernetes only uses certain parts of Docker to provide orchestration of containers? ...
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6 votes
3 answers
4k views

Developing inside a Docker image?

Every time I onboard a new person on my team I have to go through the same routine of installing everything, figuring out what changed since last time we onboarded someone etc. Not fun. I've heard ...
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  • 335
6 votes
1 answer
4k views

What are the best practices for anti-virus / anti-malware when using containers?

One of the SOC 2 controls is apparently around ensuring antivirus/anti-spam/anti-malware is running on production servers. I've been googling to see if there are any recommendation/best practices for ...
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  • 163
6 votes
2 answers
76 views

Autoscaling containers using local request counters

Somewhere around I got to know about different approaches which were used to scale our webapp which included Scaling using local request counters. Below that they had written the drawbacks of this ...
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6 votes
1 answer
1k views

Networking between Docker containers

I have a docker container 'A' on a host 10.11.12.13 listening on port 0.0.0.0:8443->8443/tcp I have another container 'B' on same host how wants to talk to 'A' on 8443 via host. Thus when I run ...
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6 votes
0 answers
68 views

Blackbox testing vs openbox testing applications in a containerized environment [closed]

We use containers to deploy our Node.js applications. But currently, the development and a good share of testing is done by the developers on their own host system and thus using different versions of ...
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6 votes
2 answers
131 views

What methods are available for connecting many-to-many containers?

I have two containers (Docker): TensorFlow container NodeJS container used as a frontend to the TensorFlow container. Both containers have TCP listeners on a port specified using environment ...
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  • 161
5 votes
1 answer
604 views

Docker Images via Container vs Dockerfile

Pardon the dumb questions, but I've been learning about Docker and container technologies and I was learning about using Dockerfiles to specify build instructions for an image, and how each ...
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5 votes
2 answers
527 views

If we are using containers do we still need to worry about configuration management at an infrastructure level?

We are about to begin our journey with containers and I am wondering if we still need to utilize something like Chef, Ansible, Terraform, etc. to ensure that our infrastructure is properly maintained? ...
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5 votes
1 answer
242 views

Advantages of Linux Containers over Docker

I'd like to understand the differences between Linux Containers and Docker, especially what kind of advantages Containers have in comparison to Docker.
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5 votes
1 answer
4k views

Does Docker on MacOS support tmpfs?

I am new to Docker and I want to run Docker with ram only storage. In other words, I do not want Docker to save anything on persistent storage. I found out that on Linux Docker supports tmpfs. Is ...
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5 votes
2 answers
3k views

Docker swarm join linux container Error - remote CA does not match fingerprint

Start docker swarm : docker swarm init --advertise-addr MANAGER-IP Join docker swarm: docker swarm join --token MANAGER-IP:2377 I am using Windows 10, it is working fine with Windows container mode,...
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  • 243
5 votes
1 answer
114 views

Defined start sequence of containers

AFAIK you cannot influence the order how Docker Swarm starts containers for services. Is that possible with: Mesos? K8s (Kubernetes)? Rancher? Other? This question is not about specific ...
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5 votes
2 answers
327 views

Load balancing kubernetes cluster on budget KVM provider?

There are a lot of cheap KVM providers these days that offer simple nodes with just a single external IP per node, without any load balancing. What is a typical budget load balancing solution for ...
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  • 257
5 votes
4 answers
2k views

ERROR: Unable to read database state: No such file or directory

I was trying to install Photon by pulling the docker image. But when I run docker build -t photon . I am getting the below error. ---> Running in 3076fb42ef8b ERROR: Unable to read database state:...
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4 votes
4 answers
238 views

DevOps tools and automation of manual processes

This is a general question, but couldn't find a better place to ask. I'm a new DevOps member in a company, and I've been ask to "update" our DevOps technologies. Generally speaking, in what areas do ...
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  • 151
4 votes
2 answers
73 views

Docker vs Virtualisation

I am trying to understand the underlining architecture of Docker. The diagram that's been shown everywhere claims that in contrast with Virtualisation technologies such as "VirtualBox", ...
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  • 143
4 votes
2 answers
10k views

helm - cannot get resource "namespaces" in API group

I installed Kubernetes, helm on the Ubuntu 16.04.6 Box, I want to deploy kubernetes-dashboard using helm but getting below error while installing it $ helm install stable/kubernetes-dashboard --name ...
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4 votes
1 answer
7k views

docker volumes on cifs share cause permission disaster

I have a small vm running docker it only has a 20gig SSD which is more than enough for the OS + SWAP + Docker and the container images. But now I want to run a nextcloud docker image on that host. ...
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  • 349
4 votes
1 answer
1k views

Running multiple websites on Docker in isolated or shared database containers?

So I have been reading up on Docker, and I cannot quite get my head around this concept. There are literally dozens of tutorials on the web about spawning a Wordpress instance on Docker within 5 ...
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4 votes
1 answer
89 views

How can I calculate costs of deploying 1000 instances of Drupal?

What are the things that should I investigate for making an estimate of the cost of deploying 1000 instances of Drupal, for example? I was thinking in: Database space Database usage (in ops/second? ...
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  • 253
4 votes
1 answer
184 views

How not expose my backend

I'm studying Docker and how to properly publish my containers coding a very simple web application. It has only two containers, backend and frontend. I've published the source code here: https://...
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  • 43
4 votes
1 answer
479 views

Why Run Concourse CI in Kubernetes

I've just started exploring Kubernetes and Concourse CI. Learning still, so I'm still understanding all the concepts. Forgive me if this question sounds naive. Why would we deploy Concourse CI in ...
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4 votes
1 answer
1k views

How do you monitor varnish cache inside a docker container?

How do you monitor varnish cache inside a docker container? I have found many tools on Google relating to this but we are focusing only on nagios and new relic.
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4 votes
1 answer
337 views

Change docker container’s log PATH

Team: All my container logs are under /var/log/containers.. Where in kubelet or docker config can I specify this path such that logs are instead created under new path? Ex : /shared ? Instead of /var/...
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  • 151
4 votes
1 answer
803 views

Process auditing in containers

I've read numerous articles on this going back to 2013, but what I wasn't able to ascertain is whether a reliable method has yet been devised for auditing processes inside a container. This question ...
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  • 141
3 votes
1 answer
3k views

Can't make MySQL 5.7 work with Docker Compose, no matter what

I'm configuring a docker compose file, and the first step is to configure the MySQL service (so I can further use in my app service), but no matter what, I cannot enter MySQL within the container, ...
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3 votes
3 answers
1k views

Does every docker container has a a OS?

Does every container have an OS? For example, the base docker python image has a default OS in it? I couldn't find any info on Google. I am in doubt because there are some images made with Python ...
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3 votes
2 answers
7k views

VPN container providing access to host's LAN?

I'm kinda new to this Docker thing and I'm interested in getting a biffed up VPS for some containers (websites/data, mysql, nginx, rocket.chat, etc) but I wouldn't like to access them in the wild (...
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  • 133
3 votes
2 answers
2k views

How to connect to external etcd server inside of docker container (python application)?

I have a Cement application that runs inside of a docker container. In this image I have to connect to etcd. Inside of my docker image I have config that for etcd is set to localhost that I know is ...
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  • 95
3 votes
1 answer
103 views

Porting a docker container to a different Linux host OS

I'm new to Docker. I have looked at many tutorials, however, this is still not clear to me : For example, If I create a docker image on a system which is using Ubuntu as the host OS. Can I then later ...
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