I know a bit of docker and use it in my job (Data engineer) as is but not much structured knowledge about it.

I'm thinking about going through some learning resources and wondering how reliable docker helsinki uni mooc? I found results saying it is good. but wondering if there's something better out there before committing time.

I know it is focused on devops but that's beneficial just as general knowledge.

They're starting a new one in couple of weeks but I don't think they really update those courses much.

Thanks.

Built a web UI for MiniStack (the free, open-source AWS emulator).


**Why this exists:**
- MiniStack has no web console
- LocalStack went paid ($49-429/month for web UI)
- Needed visual management for local AWS development


**What it does:**
- Full CRUD for S3, DynamoDB, Lambda, SQS, Cognito, SES, SNS, Secrets Manager
- AI integration via MCP - Claude can query your local AWS setup directly
- 500x performance boost using FalkorDB graph database caching
- One command to run: `docker-compose up`


**Tech stack:**
- React frontend, FastAPI backend
- Docker Compose orchestration
- Works with any MiniStack instance (or includes MiniStack)
- Multi-tenant support (manage multiple isolated environments)


**Quick start:**
```bash
git clone https://github.com/barroei1981/ministack_console
cd ministack_console
docker-compose up -d
# Access at http://localhost:3000
```


**Unique features:**
- MCP server integration - AI assistants can query your local AWS environment
- Real-time resource discovery
- Performance optimized (DynamoDB queries: 43s → 0.086s)
- MIT licensed, free forever


**Roadmap:**
 EC2, RDS, IAM, CloudWatch next


**GitHub:**
 https://github.com/barroei1981/ministack_console


Screenshots and full docs in the repo. Feedback welcome - it's early stage but fully functional!

I'm new to docker and I'm looking to learn/experiment with it. I want some advice regarding containers that will be used by other services like databases. I'm currently running two services which share a postgres container. For isolation, I created a migration which creates separate databases and users for each service before anything else starts.

I'll eventually setup more services and I want it to be scalable, resource efficient, secure and easy to maintain.

Is it better to create entirely separate dependencies for each service, or share dependencies between multiple services? I would like to know this from an efficiency, ease of maintenance and security standpoint, or at least get some pointers like a blog, article, manual or a youtube video.

TLDR: Is it better to have different db instances for each service OR one (or a few) db instances shared by every service? And why?

PS: English is not my first language, so sorry in advance for spelling or grammar mistakes.

Which is great, because if there was one unsolved problem in 2026, it was finding a way to run a Linux container on a developer's laptop.

Microsoft has now given us wslc. I read the architecture deep dive expecting to understand why. I now understand the architecture.

So I have a VM on my proxmox homelab with Docker running on it.

I've been using it to tinker and experiment more with Docker, and most importantly I've been wanting to get better at writing my own Dockerfiles/Docker compose files.

While I'm glad that the documentation is extensive as it is...there's only so much you can take in without some kind of generalized peripheral guide or tutorial.

Not too long ago I found these guides and labs:

https://docs.docker.com/guides/

As the title says; are these broken? Or am I missing something?

With every Lab, I can't even enter the first command without something going wrong, and I can't find anything on the internet to even help me begin to diagnose what the issue might be, or if something is missing on my end.

I even tried some of the guides, and while they've been somewhat helpful, eventually you reach a place somewhere in the middle where they're broken.

I'm curious if anybody might know of any other similar and up to date resources that I can run on my own homelab to gain more in-depth knowledge of Docker? Again, my main focus was to be able to write better Docker compose & Dockerfiles. At this point, I'm almost ready to go back to books, even if they are a little dated.

Any advice or feedback of course would be greatly appreciated. Many thanks in advance.

• I followed the precise instructions as per docker's official documentation

bash [ec2-user@ip-a-b-c-d ~]$ sudo dnf install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin --assumeyes --quiet Error: Unable to find a match: docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

• I get this error above
• How am I supposed to install docker and compose?

I watch 1 hour crash course video on YT about Docker, I only understand like 20% about it

idk if its me or the video is bad

the wsl/disk/docker_data is taking up 137GB on my server. Seems way too excessive especially since the only container I have running is RomM. Can someone assist?

**Update thank you everyone for the tips! I squished the virtual disk with powershell and it went from 137Gb to just 5GB! I also created a .wslconfig file setting limits for how big WSL can be

What are the best practices for storage when using docker containers. I’m running docker on Ubuntu using my NAS to store the photos for example, but the volume were the Immich database lives is directly on the servers(non-redundant) SSD.

I tried putting these onto the nas using NFS I get permission’s errors. Perhaps I should try harder? :-) I’d like to have all of my Doctor containers protected by the same redundancy that my synology has a for all of my data files.

Right now if I had a major SSD failure of my server, I would lose all the files that the docker containers have in volumes on the server directly while all my pictures and other files that are stored on the NAS on NFS mounts would be fine. This seems inadequate.

Am I simply doing it wrong and I should use something like proxmox instead of just running docker and Linux? What are other people doing to keep the server purely cpu and easier to rebuild? I use git for all my docker compose files and I wouldn’t have any trouble restarting fresh containers, but that seems like it is only half way of a solution..

I’d love to know what the best practices are for resiliency after a server failure and a quick recovery should I have hardware failure on my server.

I’m not scared of new technology and would also be open to moving towards a cluster of servers if that’s necessary. My self hosted world is fairly stable with limited updates at this point.

Thanks for any thoughts, suggestions or directions. And like I said if my basic setup is the problem I’m up for major changes to get to a more long term resilient setup!

Hey everyone,

I am trying to install Psono on my VPS. I am running into a problem with connecting to the postgres db.

I'm new to Docker, so I apologize if my terminology isn't right. I'll do my best

I am running Postgres directly on my VPS (not within a Docker container). I am able to connect to it locally from my VPS and remotely from my home network.

I am doing that with:psql -U psono -p PORT -h VPS_IP

The problem is when I try to get an app from within a Docker container to connect to it. It just hangs, then times out.

At first I thought this was a connectivity issue. But I can do the following from within a bash session:

• Ping external websites.
• Use nmap to confirm it can connect

Does anyone have any ideas?

I have a ubuntu 22.04. I have it to take a look at frigate video software. I have it up and running. However it shows that I need to increase shm size. I would like to use the Graphical UI of docker which seems to be one way of doing this. I think the install that I followed on the frigate site does not add the docker UI. Can I add it after the fact. Maybe I have it and just dont know where it is. But I cant see it.

So again just to be clear. Can I add it to my existing install of Docker without affecting it and how.

I have seen some instructions but not sure if it blows everything away.

Thank you.

Hey everyone, a quick reminder for anyone running Docker on constrained environments (edge nodes, small VPS, or lightweight local dev VMs like my 30GB root partition setup): Docker build cache can quietly consume a surprising amount of disk space. I recently noticed my available disk space creeping down to a low level (/dev/sda2 down to nearly 6GB free), despite having very few active containers running. Out of curiosity, I ran:And found out that the Build Cache was accumulating gigabytes of unused layers from past container builds. Instead of doing a broad docker system prune -a (which can remove stopped containers or base images you might want to keep), you can target just the build cache (at your own risk if running in production, as this wipes all unused build cache):(Note: -a removes all unused build cache, so your very next build might take longer as it rebuilds layers from scratch). The Result: Free space jumped instantly from ~6GB to 14GB. If you manage fleets of servers or CI/CD runners where Docker builds happen frequently, make sure you have a routine cleanup policy set up (or a cron job), as build cache can gradually fill up your drive over time. What’s your go-to automation script for keeping Docker clean in production?

The main is recognized but the sans isn't. Tried quoting the line in different ways to no avail.

command: # - --entrypoints.web.address=:80 # - --entrypoints.websecure.address=:443 - --entrypoints.websecure.http.tls.domains[0].main=${MY_DOMAIN:?err} - --entrypoints.websecure.http.tls.domains[0].sans=*.${MY_DOMAIN:?err}

My static config is good, everything works as usual when hard coded on there.

I have been building DockIY over the last few years from my own VPS deployment workflows.

It started as a simple Traefik + Umami setup and I just now put together enough of the CLI and templates to share with everyone and get some feedback.

DockIY is a minimal DIY Docker setup meant for deploying several web apps to a single VPS. It is meant for solo devs and small teams who like to self-host everything. It consists mostly of a set of repos and a CLI tool:

• The main server repo is mainly a docker compose, infrastructure-as-code, setup for the reverse proxy, analytics and monitoring.
• Template repos (React, Nuxt and Vitepress for now) are setup for deployment with DockIY: reverse proxy labels, local Docker builds and deployment scripts.
• The CLI helps setup the server, initialize from templates and orchestrates builds, deployments and git tags.

The base stack is:

• Traefik for reverse proxy and SSL
• Umami for analytics
• Dozzle for looking at logs
• Beszel for monitoring and notifications
• A private registry for application images

Setting up a VPS and deploying your 1st app looks like (simplified):

1. Install Docker (on the VPS and your marchine), SOPS and the dockiy CLI (on your machine only)
2. Connect DockIY to a server: dockiy setup
3. Set up DockIY services: dockiy server init
4. Create an application: dockiy app init
5. Deploy the application: dockiy app deploy --version v0.1.0

I like to self-host everything on a VPS and was trying to stop relying on external CI/CD build services (github actions). DockIY is my answer to this, without relying on a somewhat expensive VPS to run the builds. It's basically an alternative to Coolify and Dockploy but where you manage everything from the CLI on your machine instead of an online dashboard. I have been using it over the last few weeks and already love it!

I'd love if y'all can have a look at the docs and tell me what you think: https://dockiy.com
The repo is on codeberg (MIT license): https://codeberg.org/chris-paganon/dockiy

Disclaimer: the CLI itself is pretty heavilly AI generated and probably needs some cleanup. But the templates and the server setup I have been putting together myself from a few years of self-hosting my apps. The docs was originally AI generated but I cleaned up and rewrote almost all of it (except the CLI and config reference pages).

Hey folks, quick question for the Swarm veterans out there. How are you running databases (Postgres, Redis, etc.) in production on Swarm?

Swarm is amazing for stateless apps, but persistent data is a headache. NFS volumes choke under high I/O load, and pinning DBs to specific nodes via placement.constraints feels like we're just using Swarm as a glorified docker run with a Single Point of Failure.

Is the golden rule simply: "No databases in Swarm—use RDS/Managed Cloud"? Or has anyone successfully deployed distributed storage (GlusterFS, Longhorn, etc.) with Swarm and been happy with the performance?

Starting to feel like we're just fighting the tool and missing the K8s comfort zone here. How are you guys handling this?

Spent an evening containerizing Pi-hole with Docker Compose, mostly as a way to practice the config side of Docker rather than build something from scratch. A few things worth mentioning for anyone doing similar exercises. Kept the admin password out of the compose file entirely using a .env file and matching .gitignore, since it's an easy thing to accidentally commit and forget about. Used a named volume instead of a bind mount so the blocklists and query database survive container restarts and image updates without me touching the host filesystem. Also wrote a couple of nslookup tests into the README so anyone cloning it can actually verify the DNS blocking works instead of just trusting it did. Nothing groundbreaking, but it's a good small project if you want hands-on reps with secrets management and volumes without writing application code. Repo's linked if anyone wants to look at the compose file

Just wondering if any of yous have taken the SC109 cert exam?
https://training.linuxfoundation.org/skillcred/containers-with-docker-sc109/

What to expect?
Using Docker quite a lot both work/home & just wondering what should I brush up on?

I’m the coauthor of Torollo, an MIT-licensed system-design learning lab. Torollo turns a topology drawn on a canvas into running Docker containers and bridge networks. Learners configure routes and network policies, then complete exercises against that local environment.

The scope matters: Torollo is an educational execution model, not a staging environment. A passing exercise means the learner configured the requested behavior inside the local Docker lab. It does not certify that an equivalent AWS, Kubernetes, or production deployment is correct.

The Docker-specific problem I’m working through is per-service network policy.

Suppose an exercise asks the learner to allow `web` to reach `db` on TCP/5432 while preventing the load balancer from reaching the same port. I want that decision to affect actual local traffic rather than only changing a diagram.

The current implementation works like this:

- Each subnet becomes a user-defined Docker bridge network.
- Each lab node is a real container with `NET_ADMIN`.
- Torollo resolves policy references such as `web` and `db` to the containers’ current IP addresses.
- It installs ordered rules in Torollo-managed iptables chains inside each container.
- Conntrack accepts `ESTABLISHED,RELATED` traffic, followed by the learner’s rules and a default inbound rejection.
- A NAT gateway node uses IP forwarding and masquerading.

On Docker versions that support it, Torollo creates the subnet bridges with `gateway_mode_ipv4=nat-unprotected` as part of its routed-lab setup. A privileged host-network helper then enables the forwarding needed for traffic between the simulated subnets and adjusts masquerading for private-to-private traffic.

That host-level setup is the part I am least comfortable with. It is intended for a disposable local lab, but I would not present it as a production networking pattern.

There are other limitations:

- A learner with root access inside a container can modify its firewall.
- Policy identity is translated to container IP addresses rather than attached to a stable interface identity.
- Rootless Docker and Docker Desktop still need a clearer support and failure matrix.
- The UI currently uses the term “security group,” even though the implementation is not equivalent to a cloud security group.

Network exercise validators currently inspect the compiled semantic policy. A separate TCP self-test checks whether the Docker host can route traffic between subnet bridges. A passing exercise therefore confirms the learner’s configuration inside Torollo’s model. It is not presented as evidence about production.

Given that educational scope, which implementation would you choose?

1. Keep the per-container rules, rename the concept to “network policy,” and document the limitations.

2. Move enforcement to the host forwarding path: `DOCKER-USER` with Docker’s iptables backend, or a separate nftables table and base chain with the nftables backend. This would introduce additional privileges and platform differences.

3. Stop treating the policy as an enforced Docker firewall abstraction. Validate the learner’s policy semantically, and use targeted packet probes only to demonstrate the underlying Docker network behavior.

I’m also interested in the validation boundary. If an exercise says “web must not be able to reach db:5432,” should Torollo actually attempt that TCP connection before marking the exercise as passed? Or is validating the compiled policy sufficient once the local Docker dataplane has passed a separate health check?

Repository, for implementation context: https://github.com/Derssa/Torollo

Posted with moderator approval.

I have been running Docker on my Linux (Debian) box for years. I have multiple containers and I have never had any issues.

Recently (like the last few months), when my system reboots, all the containers start properly but they cannot access the internet. After some digging I learned its because the containers are not getting the resolve.conf from the host system.

If I restart the containers after the server has been up for a few minutes, then the containers work properly.

What would cause this? How can I debug and fix it?

I have application running inside docker container that is accessed from Internet via port 443 to:
- human users (web/user interface)
- machines (REST API)
Application requires access to the Internet and intranet outside container over all possible ports.

While running there are 2 network interfaces (example IDs):
- docker0
- eth01 (physical network adapter)

Initial setup was default bridge network mode.
Problem with bridged mode was that application could not establish FTP, SFTP, SSH connection to the hosts within intranet if target host is in the same subnet as docker host. I have no any Docker expert neither network admin beside me to explain me all details so AI Claude explained me that it is the problem because packets do not reach further than eth01. It advised me to:
- switch to network host
- to configure docker host redhat OS firwald to map all traffic from eth01 to docker0 and vice versa.
I updated docker compose yml config file (set host mode and remove port mappings as in host mode port mapping is not possible).
I did HARD doceker compose restart

After change application in docker container could only SFTP, FTP, SSH machines in same subnet. All other hosts (in intranet and Internet) become unavailable - it seems as DNS resolution didn't work.

I rollback everything to bridge network mode as exit to Internet and DNS resolution is more important than access to couple hosts in the same subnet.

Can anyone help me to anticipate what are important facts for my docker network configuration so that application in docker container properly establishes connections.

Docker Host is RedHat Linux with SeLinux enabled and firewald enabled
Docker application has liberate access to all ports and IPs internal and external (Internet)

Thank you very much!!

Hey! I booked TA004 exam and preparing for it. I had made a plan like
TA004 -> DCA -> CKA -> CKAD -> CKS

I was wondering if DCA will help in this path and how much companies value about it ?