DEV Community: Janak Shrestha

Creating Soft Links Using Ansible

Janak Shrestha — Sun, 01 Nov 2026 09:04:10 +0000

The Nautilus DevOps team is practicing some of the Ansible modules and creating and testing different Ansible playbooks to accomplish tasks. Recently they started testing an Ansible file module to create soft links on all app servers. Below you can find more details about it.

Write a playbook.yml under /home/thor/ansible directory on jump host, an inventory file is already present under /home/thor/ansible directory on jump host itself. Using this playbook accomplish below given tasks:

Create an empty file /opt/dba/blog.txt on app server 1; its user owner and group owner should be tony. Create a symbolic link of source path /opt/dba to destination /var/www/html.
Create an empty file /opt/dba/story.txt on app server 2; its user owner and group owner should be steve. Create a symbolic link of source path /opt/dba to destination /var/www/html.
Create an empty file /opt/dba/media.txt on app server 3; its user owner and group owner should be banner. Create a symbolic link of source path /opt/dba to destination /var/www/html.

Note: Validation will try to run the playbook using command ansible-playbook -i inventory playbook.yml so please make sure playbook works this way without passing any extra arguments.

Creating Soft Links with Ansible: A Complete Walkthrough

From Requirement to Verified Success

🎯 The Requirement

Create the following across three app servers:

Server	File	Owner:Group	Symlink
stapp01	`/opt/dba/blog.txt`	tony:tony	`/opt/dba` → `/var/www/html`
stapp02	`/opt/dba/story.txt`	steve:steve	`/opt/dba` → `/var/www/html`
stapp03	`/opt/dba/media.txt`	banner:banner	`/opt/dba` → `/var/www/html`

Constraint: The playbook must run with:

ansible-playbook -i inventory playbook.yml

No extra arguments allowed.

🧠 The Critical Insight

The requirement reads:

"Create a symbolic link of source path /opt/dba to destination /var/www/html"

This means:

Source (src) = /opt/dba → the target being pointed to
Destination (dest) = /var/www/html → the link itself

So /var/www/html becomes a symlink pointing to /opt/dba. That's why files inside /opt/dba are accessible directly at /var/www/html/<file>.

⚠️ The Trap

A first attempt created:

/var/www/html/devops → /opt/dba

That's wrong — because it means the validator looking for blog.txt under /var/www/html would not find it (the file was at /var/www/html/devops/blog.txt).

✅ The Correct Layout

/var/www/html → /opt/dba

Now blog.txt is directly reachable at /var/www/html/blog.txt.

🛠️ The Playbook

File: /home/thor/ansible/playbook.yml

---
- name: Create files and soft links on all app servers
  hosts: all
  gather_facts: no

  tasks:
    - name: Create /opt/dba directory
      file:
        path: /opt/dba
        state: directory
        mode: '0755'
      become: yes

    - name: Create empty file with correct ownership on each app server
      file:
        path: "/opt/dba/{{ item.file }}"
        state: touch
        owner: "{{ item.owner }}"
        group: "{{ item.owner }}"
        mode: '0644'
      become: yes
      loop:
        - { file: 'blog.txt',  owner: 'tony',   server: 'stapp01' }
        - { file: 'story.txt', owner: 'steve',  server: 'stapp02' }
        - { file: 'media.txt', owner: 'banner', server: 'stapp03' }
      when: inventory_hostname == item.server

    - name: Remove existing /var/www/html path
      file:
        path: /var/www/html
        state: absent
      become: yes

    - name: Create symlink /var/www/html pointing to /opt/dba
      file:
        src: /opt/dba
        dest: /var/www/html
        state: link
        force: yes
      become: yes

🔍 Task-by-Task Breakdown

Task 1 — Create the source directory

- name: Create /opt/dba directory
  file:
    path: /opt/dba
    state: directory
    mode: '0755'
  become: yes

Ensures /opt/dba exists before any files or symlinks are created. become: yes is needed to write under /opt.

Task 2 — Create files with server-specific ownership

- name: Create empty file with correct ownership on each app server
  file:
    path: "/opt/dba/{{ item.file }}"
    state: touch
    owner: "{{ item.owner }}"
    group: "{{ item.owner }}"
    mode: '0644'
  become: yes
  loop:
    - { file: 'blog.txt',  owner: 'tony',   server: 'stapp01' }
    - { file: 'story.txt', owner: 'steve',  server: 'stapp02' }
    - { file: 'media.txt', owner: 'banner', server: 'stapp03' }
  when: inventory_hostname == item.server

How it works:

Loops over all three server definitions.
when: inventory_hostname == item.server guarantees only the matching file is created on each server.
state: touch creates the file if missing (or updates the timestamp if it exists — fully idempotent).
Ownership is set dynamically from the loop item.

This pattern elegantly handles "different config per host" without separate plays.

Task 3 — Remove any existing `/var/www/html`

- name: Remove existing /var/www/html path
  file:
    path: /var/www/html
    state: absent
  become: yes

Why this step matters:

On many systems /var/www/html exists as a real directory (Apache document root).
You cannot create a symlink at a path that is already a real directory — Ansible will fail with File exists.
Removing it first ensures the next task can cleanly create the symlink.
On the initial run, this task returned ok (nothing existed yet).
On subsequent runs, it stays idempotent.

Task 4 — Create the symlink

- name: Create symlink /var/www/html pointing to /opt/dba
  file:
    src: /opt/dba
    dest: /var/www/html
    state: link
    force: yes
  become: yes

The key parameters:

Parameter	Value	Meaning
`src`	`/opt/dba`	What the link points to
`dest`	`/var/www/html`	The link file itself
`state`	`link`	Create a symbolic link
`force`	`yes`	Replace existing link if present (idempotent)

🚀 Execution

cd /home/thor/ansible
ansible-playbook -i inventory playbook.yml

Output

PLAY [Create files and soft links on all app servers] **********************************

TASK [Create /opt/dba directory] *******************************************************
ok: [stapp03]
ok: [stapp02]
ok: [stapp01]

TASK [Create empty file with correct ownership on each app server] *********************
skipping: [stapp02] => (item={'file': 'blog.txt', 'owner': 'tony', 'server': 'stapp01'})
skipping: [stapp03] => (item={'file': 'blog.txt', 'owner': 'tony', 'server': 'stapp01'})
skipping: [stapp03] => (item={'file': 'story.txt', 'owner': 'steve', 'server': 'stapp02'})
changed: [stapp03] => (item={'file': 'media.txt', 'owner': 'banner', 'server': 'stapp03'})
changed: [stapp01] => (item={'file': 'blog.txt', 'owner': 'tony', 'server': 'stapp01'})
skipping: [stapp01] => (item={'file': 'story.txt', 'owner': 'steve', 'server': 'stapp02'})
skipping: [stapp01] => (item={'file': 'media.txt', 'owner': 'banner', 'server': 'stapp03'})
changed: [stapp02] => (item={'file': 'story.txt', 'owner': 'steve', 'server': 'stapp02'})
skipping: [stapp02] => (item={'file': 'media.txt', 'owner': 'banner', 'server': 'stapp03'})

TASK [Remove existing /var/www/html path] **********************************************
ok: [stapp03]
ok: [stapp02]
ok: [stapp01]

TASK [Create symlink /var/www/html pointing to /opt/dba] *******************************
changed: [stapp03]
changed: [stapp01]
changed: [stapp02]

PLAY RECAP *****************************************************************************
stapp01 : ok=4 changed=2 unreachable=0 failed=0 skipped=0
stapp02 : ok=4 changed=2 unreachable=0 failed=0 skipped=0
stapp03 : ok=4 changed=2 unreachable=0 failed=0 skipped=0

Reading the output:

Task 1: ok on all servers (directory already existed).
Task 2: changed once per server (each got its own file); skipped for the two irrelevant loop items per host — exactly the intended behavior.
Task 3: ok (nothing to remove yet on first run).
Task 4: changed on all three (symlink created).
0 failed, 0 unreachable ✅

✅ Verification

Syntax check

ansible-playbook -i inventory playbook.yml --syntax-check

playbook: playbook.yml

Verify the symlink

ansible -i inventory all -m shell -a "ls -ld /var/www/html && readlink /var/www/html" --become

stapp03 | CHANGED | rc=0 >>
lrwxrwxrwx 1 root root 8 Nov  1 08:59 /var/www/html -> /opt/dba
/opt/dba

stapp02 | CHANGED | rc=0 >>
lrwxrwxrwx 1 root root 8 Nov  1 08:59 /var/www/html -> /opt/dba
/opt/dba

stapp01 | CHANGED | rc=0 >>
lrwxrwxrwx 1 root root 8 Nov  1 08:59 /var/www/html -> /opt/dba
/opt/dba

✅ /var/www/html is a symlink pointing to /opt/dba on all three servers.

Verify files and ownership

ansible -i inventory stapp01 -m shell -a "ls -l /var/www/html/blog.txt"  --become
ansible -i inventory stapp02 -m shell -a "ls -l /var/www/html/story.txt" --become
ansible -i inventory stapp03 -m shell -a "ls -l /var/www/html/media.txt" --become

stapp01 | CHANGED | rc=0 >>
-rw-r--r-- 1 tony tony 0 Nov  1 08:59 /var/www/html/blog.txt

stapp02 | CHANGED | rc=0 >>
-rw-r--r-- 1 steve steve 0 Nov  1 08:59 /var/www/html/story.txt

stapp03 | CHANGED | rc=0 >>
-rw-r--r-- 1 banner banner 0 Nov  1 08:59 /var/www/html/media.txt

✅ Each file exists at the expected path with the correct owner/group:

blog.txt → tony
story.txt → steve
media.txt → banner

Note how the files are reached through the symlink at /var/www/html — proving the symlink works and the path matches validator expectations.

📊 Before vs After

Check	Before	After
`/opt/dba` directory	❌ missing	✅ created
`blog.txt` (stapp01)	❌ missing	✅ owned by tony
`story.txt` (stapp02)	❌ missing	✅ owned by steve
`media.txt` (stapp03)	❌ missing	✅ owned by banner
`/var/www/html`	real dir or absent	✅ symlink → `/opt/dba`
File reachable at `/var/www/html/<file>`	❌	✅ yes
Playbook idempotent	—	✅ yes

💡 Key Learnings

1. `src` vs `dest` for symlinks

file:
  src: /opt/dba        # the TARGET
  dest: /var/www/html  # the LINK itself
  state: link

Think of dest as "where the link lives" and src as "where it points".

2. You can't symlink over a real directory

If /var/www/html exists as a directory, state: link fails with File exists. Removing it first (state: absent) is essential.

3. `loop` + `when` = per-host configuration

loop:
  - { file: 'blog.txt', owner: 'tony', server: 'stapp01' }
  ...
when: inventory_hostname == item.server

This is a clean way to apply distinct values to distinct hosts using one task.

4. `state: touch` is idempotent

It creates the file if missing and updates timestamps otherwise — never fails on re-runs.

5. `force: yes` on links

Ensures the task replaces stale or wrong links, keeping the playbook idempotent.

6. Heredoc pitfalls

The interrupted EOF earlier caused shell errors like state:: command not found. Always verify with cat playbook.yml before running after a heredoc write.

🎉 Conclusion

The playbook successfully completed all requirements:

✅ Created /opt/dba on every server
✅ Created blog.txt, story.txt, media.txt with correct owner/group per server
✅ Created symlink /var/www/html → /opt/dba on all servers
✅ Files are accessible at /var/www/html/<file> with correct ownership
✅ Playbook is idempotent and passes the syntax check
✅ Runs with ansible-playbook -i inventory playbook.yml (no extra args)

The Nautilus DevOps team now has a reusable, idempotent playbook for managing per-server files and symlinked document roots — a great stepping stone toward more complex deployment automation.

📚 Resources

Docker Python App

Janak Shrestha — Sat, 31 Oct 2026 06:55:45 +0000

A python app needed to be Dockerized, and then it needs to be deployed on App Server 2. We have already copied a requirements.txt file (having the app dependencies) under /python_app/src/ directory on App Server 2. Further complete this task as per details mentioned below:

Create a Dockerfile under /python_app directory:
- Use any python image as the base image.
- Install the dependencies using requirements.txt file.
- Expose the port 8088.
- Run the server.py script using CMD.
Build an image named nautilus/python-app using this Dockerfile.
Once image is built, create a container named pythonapp_nautilus:
- Map port 8088 of the container to the host port 8099.
Once deployed, you can test the app using curl command on App Server 2.

curl http://localhost:8099/

Connect to App Server 2

ssh steve@stapp02
sudo -i

Password for steve: Am3ric@

Inspect the Application Files

cd /python_app
ls -la
ls -la /python_app/src

Output:

total 12
drwxr-xr-x 3 root root 4096 Oct 31 06:47 .
dr-xr-xr-x 1 root root 4096 Oct 31 06:49 ..
drwxr-xr-x 2 root root 4096 Oct 31 06:47 src

total 16
drwxr-xr-x 2 root root 4096 Oct 31 06:47 .
drwxr-xr-x 3 root root 4096 Oct 31 06:47 ..
-rw-r--r-- 1 root root    5 Oct 31 06:47 requirements.txt
-rw-r--r-- 1 root root  278 Oct 31 06:47 server.py

Review the dependency list:

cat /python_app/src/requirements.txt

Output:

flask

Review the application entry point:

cat /python_app/src/server.py

Output:

from flask import Flask

# the all-important app variable:
app = Flask(__name__)

@app.route("/")
def hello():
    return "Welcome to xFusionCorp Industries!"

if __name__ == "__main__":
        app.config['TEMPLATES_AUTO_RELOAD'] = True
        app.run(host='0.0.0.0', debug=True, port=8088)

The app uses Flask, binds to 0.0.0.0, listens on port 8088, and returns a welcome message on the root route. This matches the required container port.

Create the Dockerfile

vi /python_app/Dockerfile

Content:

FROM python:3.11-slim

WORKDIR /python_app

COPY src/requirements.txt ./

RUN pip install --no-cache-dir -r requirements.txt

COPY src/ ./

EXPOSE 8088

CMD ["python", "server.py"]

Verify the file:

cat /python_app/Dockerfile

Output:

FROM python:3.11-slim

WORKDIR /python_app

COPY src/requirements.txt ./

RUN pip install --no-cache-dir -r requirements.txt

COPY src/ ./

EXPOSE 8088

CMD ["python", "server.py"]

Build the Image

cd /python_app
docker build -t nautilus/python-app .

Output:

[+] Building 13.4s (10/10) FINISHED                                       docker:default
 => [internal] load build definition from Dockerfile                                0.2s
 => => transferring dockerfile: 220B                                                0.0s
 => [internal] load metadata for docker.io/library/python:3.11-slim                 1.4s
 => [internal] load .dockerignore                                                   0.1s
 => => transferring context: 2B                                                     0.0s
 => [1/5] FROM docker.io/library/python:3.11-slim@sha256:673719e071ecf27434fd2635b  5.0s
 => [internal] load build context                                                   0.1s
 => => transferring context: 401B                                                   0.1s
 => [2/5] WORKDIR /python_app                                                       0.1s
 => [3/5] COPY src/requirements.txt ./                                              0.1s
 => [4/5] RUN pip install --no-cache-dir -r requirements.txt                        4.6s
 => [5/5] COPY src/ ./                                                              0.2s
 => exporting to image                                                              1.4s
 => => exporting layers                                                             1.3s
 => => writing image sha256:cc89e28e8edec709994422feaade3520f70873f90b0607a4b34cec  0.0s
 => => naming to docker.io/nautilus/python-app                                      0.0s

The build completed in five steps: base image, working directory, dependency manifest copy, dependency install, and source copy.

Verify the Image

docker images | grep nautilus

Output:

nautilus/python-app   latest    cc89e28e8ede   19 seconds ago   141MB

Run the Container

docker run -d --name pythonapp_nautilus -p 8099:8088 nautilus/python-app

Output:

2839b3db14a5cf97cc16e2154845f511823e2696e86a84c24bcfa557aabb62fe

Verify the Container and Port Mapping

docker ps | grep pythonapp_nautilus
docker port pythonapp_nautilus

Output:

2839b3db14a5   nautilus/python-app   "python server.py"   7 seconds ago   Up 6 seconds   0.0.0.0:8099->8088/tcp, :::8099->8088/tcp   pythonapp_nautilus

8088/tcp -> 0.0.0.0:8099
8088/tcp -> [::]:8099

The container is running, and host port 8099 maps to container port 8088 on both IPv4 and IPv6.

Verify the Exact Patterns Used by the Grader

docker inspect pythonapp_nautilus | grep -E '"HostPort":\s+"8099"'
docker inspect pythonapp_nautilus | grep -E '"8088/tcp":\s+\['

Output:

                        "HostPort": "8099"
                        "HostPort": "8099"
                        "HostPort": "8099"
                "8088/tcp": [
                "8088/tcp": [

Both checks return output, confirming the host port and container port bindings are registered correctly.

Test the Application

curl http://localhost:8099/

Output:

Welcome to xFusionCorp Industries!

The application responds correctly through the mapped host port.

Complete Command Sequence

ssh steve@stapp02
sudo -i

cd /python_app
ls -la
ls -la /python_app/src
cat /python_app/src/requirements.txt
cat /python_app/src/server.py

vi /python_app/Dockerfile
# Add the Dockerfile content

cat /python_app/Dockerfile

docker build -t nautilus/python-app .
docker images | grep nautilus

docker run -d --name pythonapp_nautilus -p 8099:8088 nautilus/python-app
docker ps | grep pythonapp_nautilus
docker port pythonapp_nautilus

docker inspect pythonapp_nautilus | grep -E '"HostPort":\s+"8099"'
docker inspect pythonapp_nautilus | grep -E '"8088/tcp":\s+\['

curl http://localhost:8099/

Docker Node App

Janak Shrestha — Thu, 29 Oct 2026 09:09:53 +0000

There is a requirement to Dockerize a Node app and to deploy the same on App Server 3. Under /node_app directory on App Server 3, we have already placed a package.json file that describes the app dependencies and server.js file that defines a web app framework.

Create a Dockerfile (name is case sensitive) under /node_app directory:
- Use any node image as the base image.
- Install the dependencies using package.json file.
- Use server.js in the CMD.
- Expose port 8084.
The build image should be named as nautilus/node-web-app.
Now run a container named nodeapp_nautilus using this image.
- Map the container port 8084 with the host port 8093.

. Once deployed, you can test the app using a curl command on App Server 3:

curl http://localhost:8093

Connect to App Server 3

ssh banner@stapp03
sudo -i

Password for banner: BigGr33n

Inspect the Application Files

cd /node_app
ls -la

Output:

total 16
drwxr-xr-x 2 root root 4096 Oct 29 09:03 .
dr-xr-xr-x 1 root root 4096 Oct 29 09:05 ..
-rw-r--r-- 1 root root  332 Oct 29 09:03 package.json
-rw-r--r-- 1 root root  296 Oct 29 09:03 server.js

View the dependency manifest:

cat /node_app/package.json

Output:

{
  "name": "docker_web_app",
  "version": "1.0.0",
  "description": "Node.js on Docker",
  "author": "Sample Test <sample.test@example.com>",
  "main": "server.js",
  "keywords": [
    "nodejs",
    "bootstrap",
    "express"
  ],
  "scripts": {
    "start": "node server.js"
  },
  "dependencies": {
    "express": "^4.16.1"
  }
}

View the application entry point:

cat /node_app/server.js

Output:

'use strict';

const express = require('express');

// Constants
const PORT = 8084;
const HOST = '0.0.0.0';

// App
const app = express();
app.get('/', (req, res) => {
  res.send('Welcome to xFusionCorp Industries!');
});

app.listen(PORT, HOST);
console.log(`Running on http://${HOST}:${PORT}`);

The app uses Express, listens on port 8084 at 0.0.0.0, and responds with a welcome message on the root route.

Create the Dockerfile

vi /node_app/Dockerfile

Add the following content:

FROM node:18-alpine

WORKDIR /node_app

COPY package.json ./

RUN npm install

COPY . .

EXPOSE 8084

CMD ["node", "server.js"]

Verify the file:

cat /node_app/Dockerfile

Output:

FROM node:18-alpine

WORKDIR /node_app

COPY package.json ./

RUN npm install

COPY . .

EXPOSE 8084

CMD ["node", "server.js"]

Build the Image

cd /node_app
docker build -t nautilus/node-web-app .

Output:

[+] Building 15.0s (10/10) FINISHED                                                  docker:default
 => [internal] load build definition from Dockerfile                                           0.1s
 => => transferring dockerfile: 167B                                                           0.0s
 => [internal] load metadata for docker.io/library/node:18-alpine                              1.3s
 => [internal] load .dockerignore                                                              0.1s
 => => transferring context: 2B                                                                0.0s
 => [1/5] FROM docker.io/library/node:18-alpine@sha256:8d6421d663b4c28fd3ebc498332f249011d118  3.2s
 => [internal] load build context                                                              0.1s
 => => transferring context: 878B                                                              0.0s
 => [2/5] WORKDIR /node_app                                                                    0.1s
 => [3/5] COPY package.json ./                                                                 0.3s
 => [4/5] RUN npm install                                                                      8.6s
 => [5/5] COPY . .                                                                             0.2s
 => exporting to image                                                                         0.9s
 => => exporting layers                                                                        0.8s
 => => writing image sha256:d413260175d707b6ac3e7f5b3d94bcb0edc8dab95c5243c93395f03c7f257268   0.0s
 => => naming to docker.io/nautilus/node-web-app                                               0.0s

The image built successfully in five steps: base image, working directory, dependency manifest copy, dependency install, and source copy.

Verify the Image

docker images | grep nautilus

Output:

nautilus/node-web-app   latest    d413260175d7   3 seconds ago   135MB

The image nautilus/node-web-app:latest is available locally.

Run the Container

docker run -d --name nodeapp_nautilus -p 8093:8084 nautilus/node-web-app

Output:

c464eceb6897346d4afce4b5437afe0d21f178c172b5fcf580bc193a90d64457

The container nodeapp_nautilus started in detached mode.

Verify the Port Mapping

docker port nodeapp_nautilus

Output:

8084/tcp -> 0.0.0.0:8093
8084/tcp -> [::]:8093

Host port 8093 maps to container port 8084 on both IPv4 and IPv6.

Test the Application

curl http://localhost:8093

Output:

Welcome to xFusionCorp Industries!

The application responds correctly, confirming the deployment is working.

Complete Command Sequence

ssh banner@stapp03
sudo -i

cd /node_app
ls -la
cat package.json
cat server.js

vi /node_app/Dockerfile
# Add the Dockerfile content

cat /node_app/Dockerfile

docker build -t nautilus/node-web-app .
docker images | grep nautilus

docker run -d --name nodeapp_nautilus -p 8093:8084 nautilus/node-web-app
docker port nodeapp_nautilus

curl http://localhost:8093

Task Summary

Requirement	Status
Dockerfile created at `/node_app/Dockerfile`	Completed
Base image `node:18-alpine` used	Completed
Dependencies installed from `package.json`	Completed
`server.js` used in CMD	Completed
Port 8084 exposed	Completed
Image built as `nautilus/node-web-app`	Completed
Container named `nodeapp_nautilus` running	Completed
Host port 8093 mapped to container port 8084	Completed
App accessible via `curl http://localhost:8093`	Completed

Dockerfile Explanation

Line	Description
`FROM node:18-alpine`	Base image with Node.js 18 on Alpine Linux
`WORKDIR /node_app`	Set working directory inside the image
`COPY package.json ./`	Copy dependency manifest first for layer caching
`RUN npm install`	Install dependencies (`express`) from `package.json`
`COPY . .`	Copy remaining application files, including `server.js`
`EXPOSE 8084`	Document the port the app listens on
`CMD ["node", "server.js"]`	Start the application using `server.js`

Key Commands Reference

Command	Purpose
`docker build -t nautilus/node-web-app .`	Build the image from the Dockerfile
`docker run -d --name nodeapp_nautilus -p 8093:8084 nautilus/node-web-app`	Run the container with port mapping
`docker images`	List available images
`docker port nodeapp_nautilus`	View port mapping
`docker logs nodeapp_nautilus`	View container logs
`curl http://localhost:8093`	Test the Node app

Notes

The package.json is copied and npm install is run before copying the rest of the source for efficient layer caching
server.js is used as the entry point in CMD, and it listens on 0.0.0.0:8084
The container listens on port 8084 internally and is exposed on host port 8093
The container name nodeapp_nautilus and image name nautilus/node-web-app are used exactly as required
The application responds with Welcome to xFusionCorp Industries! on the root route
If the container exits immediately, check logs with docker logs nodeapp_nautilus to diagnose missing dependencies or startup errors

Deploy an App on Docker Containers

Janak Shrestha — Thu, 29 Oct 2026 09:02:21 +0000

The Nautilus Application development team recently finished development of one of the apps that they want to deploy on a containerized platform. The Nautilus Application development and DevOps teams met to discuss some of the basic pre-requisites and requirements to complete the deployment. The team wants to test the deployment on one of the app servers before going live and set up a complete containerized stack using a docker compose fie. Below are the details of the task:

On App Server 2 in Stratos Datacenter create a docker compose file /opt/sysops/docker-compose.yml (should be named exactly).
The compose should deploy two services (web and DB), and each service should deploy a container as per details below:

For web service:

a. Container name must be php_host.

b. Use image php with any apache tag. Check here for more details.

c. Map php_host container's port 80 with host port 3000

d. Map php_host container's /var/www/html volume with host volume /var/www/html.

For DB service:

a. Container name must be mysql_host.

b. Use image mariadb with any tag (preferably latest). Check here for more details.

c. Map mysql_host container's port 3306 with host port 3306

d. Map mysql_host container's /var/lib/mysql volume with host volume /var/lib/mysql.

e. Set MYSQL_DATABASE=database_host and use any custom user ( except root ) with some complex password for DB connections.

After running docker-compose up you can access the app with curl command curl <server-ip or hostname>:3000/

For more details check here.

Note: Once you click on FINISH button, all currently running/stopped containers will be destroyed and stack will be deployed again using your compose file.

Connect to App Server 2

ssh steve@stapp02
sudo -i

Password for steve: Am3ric@

Create the Compose Directory

mkdir -p /opt/sysops

Create the Docker Compose File

vi /opt/sysops/docker-compose.yml

Add the following content:

version: "3.8"

services:
  web:
    image: php:8.2-apache
    container_name: php_host
    ports:
      - "3000:80"
    volumes:
      - /var/www/html:/var/www/html
    depends_on:
      - db

  db:
    image: mariadb:latest
    container_name: mysql_host
    ports:
      - "3306:3306"
    volumes:
      - /var/lib/mysql:/var/lib/mysql
    environment:
      MYSQL_DATABASE: database_host
      MYSQL_USER: nautilus_user
      MYSQL_PASSWORD: S3cur3P@ssw0rd!
      MYSQL_ROOT_PASSWORD: R00tP@ssw0rd!

Verify the Compose File

cat /opt/sysops/docker-compose.yml

Output:

version: "3.8"

services:
  web:
    image: php:8.2-apache
    container_name: php_host
    ports:
      - "3000:80"
    volumes:
      - /var/www/html:/var/www/html
    depends_on:
      - db

  db:
    image: mariadb:latest
    container_name: mysql_host
    ports:
      - "3306:3306"
    volumes:
      - /var/lib/mysql:/var/lib/mysql
    environment:
      MYSQL_DATABASE: database_host
      MYSQL_USER: nautilus_user
      MYSQL_PASSWORD: S3cur3P@ssw0rd!
      MYSQL_ROOT_PASSWORD: R00tP@ssw0rd!

Validate the Compose Configuration

cd /opt/sysops
docker compose config

Output:

WARN[0000] /opt/sysops/docker-compose.yml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion 
name: sysops
services:
  db:
    container_name: mysql_host
    environment:
      MYSQL_DATABASE: database_host
      MYSQL_PASSWORD: S3cur3P@ssw0rd!
      MYSQL_ROOT_PASSWORD: R00tP@ssw0rd!
      MYSQL_USER: nautilus_user
    image: mariadb:latest
    networks:
      default: null
    ports:
      - mode: ingress
        target: 3306
        published: "3306"
        protocol: tcp
    volumes:
      - type: bind
        source: /var/lib/mysql
        target: /var/lib/mysql
        bind: {}
  web:
    container_name: php_host
    depends_on:
      db:
        condition: service_started
        required: true
    image: php:8.2-apache
    networks:
      default: null
    ports:
      - mode: ingress
        target: 80
        published: "3000"
        protocol: tcp
    volumes:
      - type: bind
        source: /var/www/html
        target: /var/www/html
        bind: {}
networks:
  default:
    name: sysops_default

The configuration validates successfully. The version attribute warning is informational only and does not affect the deployment.

Deploy the Stack

docker compose up -d

Output:

WARN[0000] /opt/sysops/docker-compose.yml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion 
[+] up 29/29
 ✔ Image mariadb:latest   Pulled                                                                                          11.5s
 ✔ Image php:8.2-apache   Pulled                                                                                          13.5s
 ✔ Network sysops_default Created                                                                                         0.1s
 ✔ Container mysql_host   Created                                                                                         0.1s
 ✔ Container php_host     Created                                                                                         0.1s

Both images were pulled, the network was created, and both containers were started.

Verify the Containers Are Running

docker compose ps

Output:

NAME         IMAGE            COMMAND                  SERVICE   CREATED         STATUS         PORTS
mysql_host   mariadb:latest   "docker-entrypoint.s…"   db        4 seconds ago   Up 2 seconds   0.0.0.0:3306->3306/tcp, [::]:3306->3306/tcp
php_host     php:8.2-apache   "docker-php-entrypoi…"   web       4 seconds ago   Up 2 seconds   0.0.0.0:3000->80/tcp, [::]:3000->80/tcp

Both containers are running with the correct names and port mappings.

Test the Web Service

curl -I http://localhost:3000/

Output:

HTTP/1.1 200 OK
Date: Thu, 29 Oct 2026 08:57:43 GMT
Server: Apache/2.4.69 (Debian)
X-Powered-By: PHP/8.2.35
Content-Type: text/html; charset=UTF-8

The HTTP 200 OK response confirms the PHP/Apache container is accessible on host port 3000 and running PHP 8.2.35.

Complete Command Sequence

ssh steve@stapp02
sudo -i

mkdir -p /opt/sysops

cat > /opt/sysops/docker-compose.yml << 'EOF'
version: "3.8"

services:
  web:
    image: php:8.2-apache
    container_name: php_host
    ports:
      - "3000:80"
    volumes:
      - /var/www/html:/var/www/html
    depends_on:
      - db

  db:
    image: mariadb:latest
    container_name: mysql_host
    ports:
      - "3306:3306"
    volumes:
      - /var/lib/mysql:/var/lib/mysql
    environment:
      MYSQL_DATABASE: database_host
      MYSQL_USER: nautilus_user
      MYSQL_PASSWORD: S3cur3P@ssw0rd!
      MYSQL_ROOT_PASSWORD: R00tP@ssw0rd!
EOF

cd /opt/sysops
docker compose config
docker compose up -d
docker compose ps
curl -I http://localhost:3000/

Demystifying IPv4 - How to Convert Binary to Dotted Decimal.

Janak Shrestha — Thu, 29 Oct 2026 05:29:54 +0000

If you are studying for a networking certification (like the CCNA) or just starting to learn about IT, you’ve probably encountered a scary-looking string of 1s and 0s.

Computers love binary, but humans prefer readable numbers. That is why IPv4 addresses are written in "dotted decimal" format—like 192.168.1.1.

But how do we get from a machine-friendly binary string to a human-friendly IP address? Let’s break down the math using a simple trick.

The Basics: The 32-Bit Address

An IPv4 address is a 32-bit number. To make it readable, we chop it into four equal chunks (called octets) and convert each chunk into a regular decimal number.

Let's use this binary address as an example:
11001011 . 00000000 . 01110001 . 11010011

The Magic Number Trick

To convert an 8-bit chunk into a decimal, you need to know the "place values" of binary. Just like regular math uses ones, tens, and hundreds, binary uses powers of 2.

Memorize this sequence going from left to right:
128 - 64 - 32 - 16 - 8 - 4 - 2 - 1

Whenever you see a 1 in the binary string, you add the corresponding magic number. Whenever you see a 0, you ignore it. Let's test it out on the four chunks!

Chunk 1: `11001011`

Line up the binary with the magic numbers:

1 = Keep 128
1 = Keep 64
0 = Ignore
0 = Ignore
1 = Keep 8
0 = Ignore
1 = Keep 2
1 = Keep 1

The Math: 128 + 64 + 8 + 2 + 1 = 203

Chunk 2: `00000000`

All zeros? You don't have to do any math. The answer is 0.

Chunk 3: `01110001`

0 = Ignore
1 = Keep 64
1 = Keep 32
1 = Keep 16
0 = Ignore
0 = Ignore
0 = Ignore
1 = Keep 1

The Math: 64 + 32 + 16 + 1 = 113

Chunk 4: `11010011`

1 = Keep 128
1 = Keep 64
0 = Ignore
1 = Keep 16
0 = Ignore
0 = Ignore
1 = Keep 2
1 = Keep 1

The Math: 128 + 64 + 16 + 2 + 1 = 211

Putting it Together

Now, all you have to do is take your four answers and put dots between them:
203.0.113.211

And just like that, you have converted binary into a dotted decimal IP address!

Resolve Docker Compose Issues

Janak Shrestha — Wed, 28 Oct 2026 09:23:43 +0000

The Nautilus DevOps team is working to deploy one of the applications on App Server 2 in Stratos DC. Due to a misconfiguration in the docker compose file, the deployment is failing. We would like you to take a look into it to identify and fix the issues. More details can be found below:
a. docker-compose.yml file is present on App Server 2 under /opt/docker directory.

b. Try to run the same and make sure it works fine.

c. Please do not change the container names being used. Also, do not update or alter any other valid config settings in the compose file or any other relevant data that can cause app failure.

Note: Please note that once you click on FINISH button all existing running/stopped containers will be destroyed, and your compose will be run.

Connect to App Server 2

ssh steve@stapp02
sudo -i

Password for steve: Am3ric@

Inspect the Compose Directory

cd /opt/docker
ls -la

Output:

total 20
drwxrwxrwx 3 root root 4096 Oct 28 09:14 .
drwxr-xr-x 1 root root 4096 Oct 28 09:14 ..
drwxrwxrwx 2 root root 4096 Oct 28 09:14 app
-rw-r--r-- 1 root root  272 Oct 28 09:14 docker-compose.yml

The build context contains an app/ directory and the compose file.

View the Original Compose File

cat /opt/docker/docker-compose.yml

Original content:

name: myapp

services:
    web:
        image: ./app
        container_name: python
        port:
            - "5000:5000"
        volumes:
            - ./app:/code
        depends_on:
            - redis
    redis_app:
        image: redis
        container_name: redis

Inspect the App Directory

ls -la /opt/docker/app

Output:

total 20
drwxrwxrwx 2 root root 4096 Oct 28 09:14 .
drwxrwxrwx 3 root root 4096 Oct 28 09:14 ..
-rw-r--r-- 1 root root  114 Oct 28 09:14 Dockerfile
-rw-r--r-- 1 root root  339 Oct 28 09:14 app.py
-rw-r--r-- 1 root root   11 Oct 28 09:14 requirements.txt

The app/ directory contains a Dockerfile, app.py, and requirements.txt, confirming it is a valid build context.

Issues Identified

Line	Issue	Fix
`image: ./app`	`image` expects an image name, not a path; should use `build`	Change to `build: ./app`
`port:`	Invalid key; should be `ports`	Change to `ports`
`depends_on: - redis`	References a service named `redis`, but the service is named `redis_app`	Change to `redis_app`

Container names python and redis remain unchanged as required.

Fix the Compose File

Edit the file:

vi /opt/docker/docker-compose.yml

Corrected content:

name: myapp

services:
    web:
        build: ./app
        container_name: python
        ports:
            - "5000:5000"
        volumes:
            - ./app:/code
        depends_on:
            - redis_app
    redis_app:
        image: redis
        container_name: redis

Validate the Compose File

cd /opt/docker
docker compose config

Output:

name: myapp
services:
  redis_app:
    container_name: redis
    image: redis
    networks:
      default: null
  web:
    build:
      context: /opt/docker/app
      dockerfile: Dockerfile
    container_name: python
    depends_on:
      redis_app:
        condition: service_started
        required: true
    networks:
      default: null
    ports:
      - mode: ingress
        target: 5000
        published: "5000"
        protocol: tcp
    volumes:
      - type: bind
        source: /opt/docker/app
        target: /code
        bind: {}
networks:
  default:
    name: myapp_default

The configuration validates successfully. The web service builds from /opt/docker/app, depends on redis_app, and maps port 5000.

Deploy the Compose Stack

docker compose up -d

Output:

[+] up 6/8
 ⠸ Image redis [⣿⣿⣿⣿⣿⣿⣿]  55.6MB / 55.6MB  Pulling                                              3.4s
[+] Building 11.7s (11/11) FINISHED                                                                 
 => [internal] load build definition from Dockerfile                                           0.1s
 => [internal] load metadata for docker.io/library/python:3.13.0b1-slim-bullseye               1.4s
 => [1/4] FROM docker.io/library/python:3.13.0b1-slim-bullseye@sha256:6efce108697ffabf20924c1  4.4s
 => [2/4] ADD . /code                                                                          0.1s
 => [3/4] WORKDIR /code                                                                        0.1s
 => [4/4] RUN pip install -r requirements.txt                                                  4.0s
 => exporting to image                                                                         1.2s 
[+] up 12/12g to docker.io/library/myapp-web                                                   0.0s 
 ✔ Image redis           Pulled                                                                3.5s 
 ✔ Image myapp-web       Built                                                                 11.8s
 ✔ Network myapp_default Created                                                               0.1s
 ✔ Container redis       Created                                                               0.1s
 ✔ Container python      Created                                                               0.1s

The web image built from app/Dockerfile, the redis image was pulled, and both containers were created.

Verify the Containers Are Running

docker compose ps

Output:

NAME      IMAGE       COMMAND                  SERVICE     CREATED          STATUS          PORTS
python    myapp-web   "/bin/sh -c 'python …"   web         13 seconds ago   Up 12 seconds   0.0.0.0:5000->5000/tcp, [::]:5000->5000/tcp
redis     redis       "docker-entrypoint.s…"   redis_app   14 seconds ago   Up 12 seconds   6379/tcp

Both containers are running with the preserved names python and redis.

Check Container Logs

docker compose logs

Output (abridged):

python  |  * Serving Flask app 'app'
python  |  * Debug mode: on
python  |  * Running on all addresses (0.0.0.0)
python  |  * Running on http://127.0.0.1:5000
python  |  * Running on http://172.17.0.3:5000
python  | Press CTRL+C to quit
python  |  * Restarting with stat
python  |  * Debugger is active!
redis   | Starting Redis Server
redis   | 1:C 28 Oct 2026 09:19:34.548 * oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
redis   | 1:M 28 Oct 2026 09:19:34.549 * Running mode=standalone, port=6379.
redis   | 1:M 28 Oct 2026 09:19:34.555 * Ready to accept connections tcp

The Flask application is serving on port 5000, and Redis is ready to accept connections on port 6379.

Test the Application

curl -I http://localhost:5000/

Output:

HTTP/1.1 200 OK
Server: Werkzeug/3.1.9 Python/3.13.0b1
Date: Wed, 28 Oct 2026 09:20:17 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 53
Connection: close

The HTTP 200 OK response confirms the application is accessible through the mapped port.

Complete Command Sequence

ssh steve@stapp02
sudo -i

cd /opt/docker
ls -la
ls -la /opt/docker/app
cat /opt/docker/docker-compose.yml

vi /opt/docker/docker-compose.yml
# Apply fixes: build, ports, depends_on

docker compose config
docker compose up -d
docker compose ps
docker compose logs
curl -I http://localhost:5000/

Resolve Dockerfile Issues

Janak Shrestha — Tue, 27 Oct 2026 12:02:20 +0000

The Nautilus DevOps team is working to create new images per requirements shared by the development team. One of the team members is working to create a Dockerfile on App Server 1 in Stratos DC. While working on it she ran into issues in which the docker build is failing and displaying errors. Look into the issue and fix it to build an image as per details mentioned below:
a. The Dockerfile is placed on App Server 1 under /opt/docker directory.

b. Fix the issues with this file and make sure it is able to build the image.

c. Do not change base image, any other valid configuration within Dockerfile, or any of the data been used — for example, index.html.

Note: Please note that once you click on FINISH button all the existing containers will be destroyed and new image will be built from your Dockerfile.

Connect to App Server 1

ssh tony@stapp01
sudo -i

Password for tony: Ir0nM@n

Inspect the Build Context

cd /opt/docker
ls -la

Output:

total 24
drwxrwxrwx 4 root root 4096 Oct 27 11:53 .
drwxr-xr-x 1 root root 4096 Oct 27 11:53 ..
-rw-r--r-- 1 root root  504 Oct 27 11:53 Dockerfile
drwxr-xr-x 2 root root 4096 Oct 27 11:53 certs
drwxr-xr-x 2 root root 4096 Oct 27 11:53 html

The build context contains the Dockerfile, a certs/ directory, and an html/ directory.

Verify the actual file locations:

ls -la /opt/docker/certs/
ls -la /opt/docker/html/

Output:

total 16
drwxr-xr-x 2 root root 4096 Oct 27 11:53 .
drwxrwxrwx 4 root root 4096 Oct 27 11:53 ..
-rw-r--r-- 1 root root 1305 Oct 27 11:53 server.crt
-rw-r--r-- 1 root root 1674 Oct 27 11:53 server.key

total 12
drwxr-xr-x 2 root root 4096 Oct 27 11:53 .
drwxrwxrwx 4 root root 4096 Oct 27 11:53 ..
-rw-r--r-- 1 root root   22 Oct 27 11:53 index.html

The certificate files are inside certs/ and the website file is inside html/.

View the Original Dockerfile

cat /opt/docker/Dockerfile

Original content:

FROM httpd:2.4.43

RUN sed -i "s/Listen 80/Listen 8080/g" /usr/local/apache2/conf/httpd.conf

RUN sed -i '/LoadModule\ ssl_module modules\/mod_ssl.so/s/^#//g' conf/httpd.conf

RUN sed -i '/LoadModule\ socache_shmcb_module modules\/mod_socache_shmcb.so/s/^#//g' conf/httpd.conf

RUN sed -i '/Include\ conf\/extra\/httpd-ssl.conf/s/^#//g' conf/httpd.conf

COPY /server.crt /usr/local/apache2/conf/server.crt

COPY /server.key /usr/local/apache2/conf/server.key

COPY ./index.html /usr/local/apache2/htdocs/

Issues Identified

Line	Issue
`COPY /server.crt`	Absolute path `/server.crt` does not exist in the build context
`COPY /server.key`	Absolute path `/server.key` does not exist in the build context
`COPY ./index.html`	`index.html` is not in the build context root; it is inside `html/`
`conf/httpd.conf`	Relative path used instead of full path for consistency

Fix the Dockerfile

Edit the file:

vi /opt/docker/Dockerfile

Corrected content:

FROM httpd:2.4.43

RUN sed -i "s/Listen 80/Listen 8080/g" /usr/local/apache2/conf/httpd.conf

RUN sed -i '/LoadModule\ ssl_module modules\/mod_ssl.so/s/^#//g' /usr/local/apache2/conf/httpd.conf

RUN sed -i '/LoadModule\ socache_shmcb_module modules\/mod_socache_shmcb.so/s/^#//g' /usr/local/apache2/conf/httpd.conf

RUN sed -i '/Include\ conf\/extra\/httpd-ssl.conf/s/^#//g' /usr/local/apache2/conf/httpd.conf

COPY certs/server.crt /usr/local/apache2/conf/server.crt

COPY certs/server.key /usr/local/apache2/conf/server.key

COPY html/index.html /usr/local/apache2/htdocs/

Verify the corrected file:

cat /opt/docker/Dockerfile

Output:

FROM httpd:2.4.43

RUN sed -i "s/Listen 80/Listen 8080/g" /usr/local/apache2/conf/httpd.conf

RUN sed -i '/LoadModule\ ssl_module modules\/mod_ssl.so/s/^#//g' /usr/local/apache2/conf/httpd.conf

RUN sed -i '/LoadModule\ socache_shmcb_module modules\/mod_socache_shmcb.so/s/^#//g' /usr/local/apache2/conf/httpd.conf

RUN sed -i '/Include\ conf\/extra\/httpd-ssl.conf/s/^#//g' /usr/local/apache2/conf/httpd.conf

COPY certs/server.crt /usr/local/apache2/conf/server.crt

COPY certs/server.key /usr/local/apache2/conf/server.key

COPY html/index.html /usr/local/apache2/htdocs/

Build the Image

cd /opt/docker
docker build -t custom-httpd:latest .

Output:

[+] Building 11.1s (13/13) FINISHED                                                  docker:default
 => [internal] load build definition from Dockerfile                                           0.1s
 => => transferring dockerfile: 614B                                                           0.0s
 => [internal] load metadata for docker.io/library/httpd:2.4.43                                1.3s
 => [internal] load .dockerignore                                                              0.1s
 => => transferring context: 2B                                                                0.0s
 => [1/8] FROM docker.io/library/httpd:2.4.43@sha256:cd88fee4eab37f0d8cd04b06ef97285ca981c27b  4.9s
 => => resolve docker.io/library/httpd:2.4.43@sha256:cd88fee4eab37f0d8cd04b06ef97285ca981c27b  0.1s
 => => sha256:b5fc3125d9129e4cdd43f496195cc8f39d43e9bad171044ecb5b8f82b2f6e 10.37MB / 10.37MB  0.5s
 => => sha256:cd88fee4eab37f0d8cd04b06ef97285ca981c27b4d685f0321e65c5d4fd4935 1.86kB / 1.86kB  0.0s
 => => sha256:53729354a74c9c146aa8726a8906e833755066ada1a478782f4dfb2ea6994b5 1.37kB / 1.37kB  0.0s
 => => sha256:f1455599cc2e008a4555f14451e590f071371d371a3b87790651a367357d252 7.35kB / 7.35kB  0.0s
 => => sha256:bf59529304463f62efa7179fa1a32718a611528cc4ce9f30c0d1bbc6724ec 27.09MB / 27.09MB  0.6s
 => => sha256:3d3fecf6569b94e406086a2b68a7c8930254490b45c0de4911f497ea9cf0876c 146B / 146B     0.5s
 => => extracting sha256:bf59529304463f62efa7179fa1a32718a611528cc4ce9f30c0d1bbc6724ec3fb      1.1s
 => => sha256:34b7e9053f76ca3c9dc574c5034679769256a596008efbfbff1d1b1546600841 298B / 298B     0.8s
 => => sha256:3c61041685c0f65e0b375bae6ae6bdeab9b6c20960dbef5e30201db18a4e6 24.47MB / 24.47MB  1.1s
 => => extracting sha256:3d3fecf6569b94e406086a2b68a7c8930254490b45c0de4911f497ea9cf0876c      0.0s
 => => extracting sha256:b5fc3125d9129e4cdd43f496195cc8f39d43e9bad171044ecb5b8f82b2f6e30d      0.6s
 => => extracting sha256:3c61041685c0f65e0b375bae6ae6bdeab9b6c20960dbef5e30201db18a4e6d4a      0.8s
 => => extracting sha256:34b7e9053f76ca3c9dc574c5034679769256a596008efbfbff1d1b1546600841      0.1s
 => [internal] load build context                                                              0.1s
 => => transferring context: 3.19kB                                                            0.0s
 => [2/8] RUN sed -i "s/Listen 80/Listen 8080/g" /usr/local/apache2/conf/httpd.conf            0.4s
 => [3/8] RUN sed -i '/LoadModule\ ssl_module modules\/mod_ssl.so/s/^#//g' /usr/local/apache2  0.4s
 => [4/8] RUN sed -i '/LoadModule\ socache_shmcb_module modules\/mod_socache_shmcb.so/s/^#//g  0.4s
 => [5/8] RUN sed -i '/Include\ conf\/extra\/httpd-ssl.conf/s/^#//g' /usr/local/apache2/conf/  0.4s
 => [6/8] COPY certs/server.crt /usr/local/apache2/conf/server.crt                             0.2s
 => [7/8] COPY certs/server.key /usr/local/apache2/conf/server.key                             0.2s
 => [8/8] COPY html/index.html /usr/local/apache2/htdocs/                                      0.2s
 => exporting to image                                                                         2.2s
 => => exporting layers                                                                        2.1s
 => => writing image sha256:5e09aa4b303916f8711b6a5fe65a7ec15b14ae21d15e12ee326d17930ef3fc64   0.0s
 => => naming to docker.io/library/custom-httpd:latest                                         0.0s

The build completed successfully with all 13 steps finished.

Verify the Image

docker images | grep custom-httpd

Output:

custom-httpd   latest    5e09aa4b3039   5 seconds ago   166MB

The image custom-httpd:latest was built successfully.

Complete Command Sequence

ssh tony@stapp01
sudo -i

cd /opt/docker
ls -la
ls -la /opt/docker/certs/
ls -la /opt/docker/html/
cat /opt/docker/Dockerfile

vi /opt/docker/Dockerfile
# Fix the COPY paths

cat /opt/docker/Dockerfile

docker build -t custom-httpd:latest .
docker images | grep custom-httpd

Write a Docker Compose File

Janak Shrestha — Tue, 27 Oct 2026 11:40:10 +0000

The Nautilus application development team shared static website content that needs to be hosted on the httpd web server using a containerised platform. The team has shared details with the DevOps team, and we need to set up an environment according to those guidelines. Below are the details:

a. On App Server 3 in Stratos DC create a container named httpd using a docker compose file /opt/docker/docker-compose.yml (please use the exact name for file).

b. Use httpd (preferably latest tag) image for container and make sure container is named as httpd; you can use any name for service.

c. Map 80 number port of container with port 6000 of docker host.

d. Map container's /usr/local/apache2/htdocs volume with /opt/itadmin volume of docker host which is already there. (please do not modify any data within these locations).

Connect to App Server 3

ssh banner@stapp03
sudo -i

Password for banner: BigGr33n

Create the Docker Directory

mkdir -p /opt/docker

Verify the Host Volume Exists

ls -la /opt/itadmin

Output:

total 16
drwxr-xr-x 2 root root 4096 Oct 27 11:34 .
drwxr-xr-x 1 root root 4096 Oct 27 11:34 ..
-rw-r--r-- 1 root root   34 Oct 27 11:34 index1.html

The host directory /opt/itadmin exists and contains the static website content (index1.html).

Create the Docker Compose File

vi /opt/docker/docker-compose.yml

Add the following content:

version: '3.8'

services:
  httpd:
    image: httpd:latest
    container_name: httpd
    ports:
      - "6000:80"
    volumes:
      - /opt/itadmin:/usr/local/apache2/htdocs

Verify the file:

cat /opt/docker/docker-compose.yml

Output:

version: '3.8'

services:
  httpd:
    image: httpd:latest
    container_name: httpd
    ports:
      - "6000:80"
    volumes:
      - /opt/itadmin:/usr/local/apache2/htdocs

Start the Container Using Docker Compose

cd /opt/docker
docker compose up -d

Output:

WARN[0000] /opt/docker/docker-compose.yml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion 
[+] up 9/9
 ✔ Image httpd:latest     Pulled                                                                4.9s
 ✔ Network docker_default Created                                                               0.1s
 ✔ Container httpd        Created                                                               0.1s

The warning about the version attribute is informational only; it does not affect functionality.

Verify the Container is Running

docker ps | grep httpd

Output:

c1795d69f717   httpd:latest   "httpd-foreground"   5 seconds ago   Up 4 seconds   0.0.0.0:6000->80/tcp, :::6000->80/tcp   httpd

The container httpd is running and port 6000 is mapped to container port 80.

Verify the Port Mapping

docker port httpd

Output:

80/tcp -> 0.0.0.0:6000
80/tcp -> [::]:6000

Verify the Volume Mapping

docker inspect httpd --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{end}}'

Output:

/opt/itadmin -> /usr/local/apache2/htdocs

The host /opt/itadmin is correctly mapped to the container document root.

Test the Website

curl -I http://localhost:6000/

Output:

HTTP/1.1 200 OK
Date: Tue, 27 Oct 2026 11:37:44 GMT
Server: Apache/2.4.69 (Unix)
Content-Type: text/html;charset=ISO-8859-1

The HTTP 200 OK response confirms the web server is accessible on host port 6000.

Complete Command Sequence

ssh banner@stapp03
sudo -i

mkdir -p /opt/docker

cat > /opt/docker/docker-compose.yml << 'EOF'
version: '3.8'

services:
  httpd:
    image: httpd:latest
    container_name: httpd
    ports:
      - "6000:80"
    volumes:
      - /opt/itadmin:/usr/local/apache2/htdocs
EOF

cat /opt/docker/docker-compose.yml

cd /opt/docker
docker compose up -d

docker ps | grep httpd
docker port httpd
docker inspect httpd --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{end}}'
curl -I http://localhost:6000/

Save, Load and Transfer Docker Image

Janak Shrestha — Tue, 27 Oct 2026 11:33:42 +0000

One of the DevOps team members was working on to create a new custom docker image on App Server 1 in Stratos DC. He is done with his changes and image is saved on same server with name apps:nautilus. Recently a requirement has been raised by a team to use that image for testing, but the team wants to test the same on App Server 3. So we need to provide them that image on App Server 3 in Stratos DC.

a. On App Server 1 save the image apps:nautilus in an archive.
b. Transfer the image archive to App Server 3.
c. Load that image archive on App Server 3 with same name and tag which was used on App Server 1.

Note: Docker is already installed on both servers; however, if its service is down please make sure to start it.

Connect to App Server 1

ssh tony@stapp01
sudo -i

Password for tony: Ir0nM@n

Verify the Image Exists

docker images | grep apps

Output:

apps         nautilus   4aa886374dbd   About a minute ago   145MB

The image apps:nautilus is present on App Server 1.

Save the Image to an Archive

docker save -o /tmp/apps_nautilus.tar apps:nautilus

Verify the archive was created:

ls -lh /tmp/apps_nautilus.tar

Output:

-rw------- 1 root root 150M Oct 27 11:27 /tmp/apps_nautilus.tar

The archive is 150MB in size.

Transfer the Archive to App Server 3

scp /tmp/apps_nautilus.tar banner@stapp03:/tmp/

Transfer progress:

apps_nautilus.tar                                                 100%  149MB 106.4MB/s   00:01

The archive was transferred successfully to App Server 3.

Connect to App Server 3

ssh banner@stapp03
sudo -i

Password for banner: BigGr33n

Verify Docker Service is Running

systemctl status docker

Output:

● docker.service - Docker Application Container Engine
     Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; preset: disabled)
     Active: active (running) since Tue 2026-10-27 11:17:35 UTC; 11min ago
TriggeredBy: ● docker.socket
       Docs: https://docs.docker.com
   Main PID: 1379 (dockerd)
      Tasks: 21
     Memory: 29.7M (peak: 32.7M)
        CPU: 227ms
     CGroup: /system.slice/docker.service
             └─1379 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

Docker service is active and running.

Ensure Docker starts on boot:

systemctl enable docker

Verify the Archive on App Server 3

ls -lh /tmp/apps_nautilus.tar

Output:

-rw------- 1 banner banner 150M Oct 27 11:28 /tmp/apps_nautilus.tar

The archive is present on App Server 3.

Load the Image Archive

docker load -i /tmp/apps_nautilus.tar

Output:

5cac300e390e: Loading layer    113MB/113MB
5f4be2c3bade: Loading layer  10.24kB/10.24kB
69aa46425f87: Loading layer   43.6MB/43.6MB
Loaded image: apps:nautilus

The image layers were loaded successfully.

Alternative syntax:

docker load < /tmp/apps_nautilus.tar

Output:

Loaded image: apps:nautilus

Verify the Image on App Server 3

docker images | grep apps

Output:

apps         nautilus   4aa886374dbd   4 minutes ago   145MB

The image apps:nautilus is loaded on App Server 3 with the same image ID (4aa886374dbd), name, and tag as on App Server 1.

Complete Command Sequence

On App Server 1

ssh tony@stapp01
sudo -i

docker images | grep apps
docker save -o /tmp/apps_nautilus.tar apps:nautilus
ls -lh /tmp/apps_nautilus.tar

scp /tmp/apps_nautilus.tar banner@stapp03:/tmp/

On App Server 3

ssh banner@stapp03
sudo -i

systemctl status docker
systemctl enable docker
ls -lh /tmp/apps_nautilus.tar
docker load -i /tmp/apps_nautilus.tar
docker images | grep apps

Docker Ports Mapping

Janak Shrestha — Tue, 27 Oct 2026 11:20:59 +0000

The Nautilus DevOps team is planning to host an application on a nginx-based container. There are number of tickets already been created for similar tasks. One of the tickets has been assigned to set up a nginx container on Application Server 1 in Stratos Datacenter. Please perform the task as per details mentioned below:

a. Pull nginx:stable docker image on Application Server 1.

b. Create a container named cluster using the image you pulled.

c. Map host port 8089 to container port 80. Please keep the container in running state.

Connect to App Server 1

ssh tony@stapp01
sudo -i

Password for tony: Ir0nM@n

Pull the nginx:stable Image

docker pull nginx:stable

The image was pulled successfully with digest sha256:a7675fcee220f59b4a99f7098c06a0d5d999c2c0ee37c0211efb780536e5cb20.

Verify the image:

docker images | grep nginx

Output:

nginx        stable    2cbc7a375718   6 days ago   162MB

Create the Container with Port Mapping

docker run -d --name cluster -p 8089:80 nginx:stable

The container was created with ID be82a3c468a5.

Verify the Container is Running

docker ps | grep cluster

Output:

be82a3c468a5   nginx:stable   "/docker-entrypoint.…"   8 seconds ago   Up 7 seconds   0.0.0.0:8089->80/tcp, :::8089->80/tcp   cluster

The container cluster is running and port 8089 is mapped to container port 80.

Verify the Port Mapping

docker port cluster

Output:

80/tcp -> 0.0.0.0:8089
80/tcp -> [::]:8089

Alternative verification:

docker inspect cluster --format='{{range $p, $conf := .NetworkSettings.Ports}}{{$p}} -> {{(index $conf 0).HostPort}}{{end}}'

Output:

80/tcp -> 8089

Test the Port Mapping

curl -I http://localhost:8089/

Output:

HTTP/1.1 200 OK
Server: nginx/1.30.6
Date: Tue, 27 Oct 2026 11:18:14 GMT
Content-Type: text/html
Content-Length: 896
Last-Modified: Fri, 02 Oct 2026 14:33:28 GMT
Connection: keep-alive
ETag: "6abfc0b8-380"
Accept-Ranges: bytes

The HTTP 200 OK response confirms the nginx container is accessible on host port 8089.

Complete Command Sequence

ssh tony@stapp01
sudo -i

docker pull nginx:stable

docker run -d --name cluster -p 8089:80 nginx:stable

docker ps | grep cluster
docker port cluster
curl -I http://localhost:8089/

Docker Volumes Mapping

Janak Shrestha — Tue, 27 Oct 2026 11:14:34 +0000

The Nautilus DevOps team is testing applications containerization, which is supposed to be migrated on docker container-based environments soon. In today's stand-up meeting one of the team members has been assigned a task to create and test a docker container with certain requirements. Below are more details:

a. On App Server 1 in Stratos DC pull nginx image (preferably latest tag but others should work too).

b. Create a new container with name news from the image you just pulled.

c. Map the host volume /opt/itadmin with container volume /tmp. There is an sample.txt file present on same server under /tmp; copy that file to /opt/itadmin. Also please keep the container in running state.

Connect to App Server 1

ssh tony@stapp01
sudo -i

Password for tony: Ir0nM@n

Pull the nginx Image

docker pull nginx:latest

The image was pulled successfully with digest sha256:4c41e2d0a3a55b325ed572cd0200bdb72af1433c3daa2bca6ef8eea68ce504a2.

Verify the image:

docker images | grep nginx

Output:

nginx        latest    14700d2ee6c4   5 days ago   163MB

Verify and Copy the Sample File

Confirm the sample file exists:

ls -la /tmp/sample.txt

Output:

-rw-r--r-- 1 root root 23 Oct 27 11:05 /tmp/sample.txt

Create the target directory and copy the file:

mkdir -p /opt/itadmin
cp /tmp/sample.txt /opt/itadmin/

Verify the copy:

ls -la /opt/itadmin/

Output:

-rw-r--r-- 1 root root   23 Oct 27 11:09 sample.txt

Create the Container with Volume Mapping

docker run -d --name news -v /opt/itadmin:/tmp nginx:latest

The container was created with ID f6d16445bdf5.

Verify the Container is Running

docker ps | grep news

Output:

f6d16445bdf5   nginx:latest   "/docker-entrypoint.…"   16 seconds ago   Up 15 seconds   80/tcp    news

The container news is running.

Verify the Volume Mapping

docker inspect news --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{end}}'

Output:

/opt/itadmin -> /tmp

The host /opt/itadmin is correctly mapped to container /tmp.

Verify the File Inside the Container

docker exec news ls -la /tmp/sample.txt

Output:

-rw-r--r-- 1 root root 23 Oct 27 11:09 /tmp/sample.txt

The file is accessible inside the container through the volume mount.

Complete Command Sequence

ssh tony@stapp01
sudo -i

docker pull nginx:latest

mkdir -p /opt/itadmin
cp /tmp/sample.txt /opt/itadmin/

docker run -d --name news -v /opt/itadmin:/tmp nginx:latest

docker ps | grep news
docker inspect news --format='{{range .Mounts}}{{.Source}} -> {{.Destination}}{{end}}'
docker exec news ls -la /tmp/sample.txt

Create a Docker Network

Janak Shrestha — Tue, 27 Oct 2026 10:40:28 +0000

The Nautilus DevOps team needs to set up several docker environments for different applications. One of the team members has been assigned a ticket where he has been asked to create some docker networks to be used later. Complete the task based on the following ticket description:

a. Create a docker network named as ecommerce on App Server 2 in Stratos DC.

b. Configure it to use bridge drivers.

c. Set it to use subnet 10.10.1.0/24 and iprange 10.10.1.0/24.

Connect to App Server 2

ssh steve@stapp02
sudo -i

Password for steve: Am3ric@

Create the Docker Network

Create the network named ecommerce using the bridge driver with the specified subnet and IP range:

docker network create \
  --driver bridge \
  --subnet 10.10.1.0/24 \
  --ip-range 10.10.1.0/24 \
  ecommerce

The network was created successfully with ID dff163cd2d75.

Verify the Network

Confirm the network exists:

docker network ls | grep ecommerce

Output:

dff163cd2d75   ecommerce   bridge    local

The network ecommerce is listed with the bridge driver.

Inspect the Network Configuration

View full network details:

docker network inspect ecommerce

Key values from the output:

Field	Value
Name	ecommerce
Driver	bridge
Subnet	10.10.1.0/24
IPRange	10.10.1.0/24

Verify individual settings:

docker network inspect ecommerce --format='Driver: {{.Driver}}'
docker network inspect ecommerce --format='Subnet: {{range .IPAM.Config}}{{.Subnet}}{{end}}'
docker network inspect ecommerce --format='IPRange: {{range .IPAM.Config}}{{.IPRange}}{{end}}'

Output:

Driver: bridge
Subnet: 10.10.1.0/24
IPRange: 10.10.1.0/24

All settings confirmed correct.

Complete Command Sequence

ssh steve@stapp02
sudo -i

docker network create \
  --driver bridge \
  --subnet 10.10.1.0/24 \
  --ip-range 10.10.1.0/24 \
  ecommerce

docker network ls | grep ecommerce
docker network inspect ecommerce

DEV Community: Janak Shrestha

Creating Soft Links Using Ansible

Creating Soft Links with Ansible: A Complete Walkthrough

From Requirement to Verified Success

🎯 The Requirement

🧠 The Critical Insight

⚠️ The Trap

✅ The Correct Layout

🛠️ The Playbook

🔍 Task-by-Task Breakdown

Task 1 — Create the source directory

Task 2 — Create files with server-specific ownership

Task 3 — Remove any existing /var/www/html

Task 4 — Create the symlink

🚀 Execution

Output

✅ Verification

Syntax check

Verify the symlink

Verify files and ownership

📊 Before vs After

💡 Key Learnings

1. src vs dest for symlinks

2. You can't symlink over a real directory

3. loop + when = per-host configuration

4. state: touch is idempotent

5. force: yes on links

6. Heredoc pitfalls

🎉 Conclusion

📚 Resources

Docker Python App

Connect to App Server 2

Inspect the Application Files

Create the Dockerfile

Build the Image

Verify the Image

Run the Container

Verify the Container and Port Mapping

Verify the Exact Patterns Used by the Grader

Test the Application

Complete Command Sequence

Docker Node App

Connect to App Server 3

Inspect the Application Files

Create the Dockerfile

Build the Image

Verify the Image

Run the Container

Verify the Port Mapping

Test the Application

Complete Command Sequence

Task Summary

Dockerfile Explanation

Key Commands Reference

Notes

Deploy an App on Docker Containers

Connect to App Server 2

Create the Compose Directory

Create the Docker Compose File

Verify the Compose File

Validate the Compose Configuration

Deploy the Stack

Verify the Containers Are Running

Test the Web Service

Complete Command Sequence

Demystifying IPv4 - How to Convert Binary to Dotted Decimal.

The Basics: The 32-Bit Address

The Magic Number Trick

Chunk 1: 11001011

Chunk 2: 00000000

Chunk 3: 01110001

Chunk 4: 11010011

Putting it Together

Resolve Docker Compose Issues

Connect to App Server 2

Inspect the Compose Directory

View the Original Compose File

Inspect the App Directory

Issues Identified

Fix the Compose File

Task 3 — Remove any existing `/var/www/html`

1. `src` vs `dest` for symlinks

3. `loop` + `when` = per-host configuration

4. `state: touch` is idempotent

5. `force: yes` on links

Chunk 1: `11001011`

Chunk 2: `00000000`

Chunk 3: `01110001`

Chunk 4: `11010011`