3. Volume Mapping & Access on Web Server

🎯 Objective

Identify and resolve issues where a Docker container fails to stay running, stops unexpectedly, or is misconfigured, with or without removing the container.

🧠 Common Symptoms

🔍 Step-by-Step Troubleshooting

1️⃣ Check Running Containers

dockerps

2️⃣ Check All Containers (Including Stopped)

dockerps-a

3️⃣ Inspect Logs

docker logs <container_name>

🧩 Log Analysis

⚠️ Warning (Safe)

AH00558: Could not reliably determine the server's fully qualified domain name

✔ Not critical

❌ Critical Issue

caught SIGWINCH, shutting down gracefully

❗ Container started → then exited

# 🛠️ Fix Without Removing Container (When Possible)

✅ Case 1 — Container Stopped Only

dockerstart <container_name>

✔ Works if:

⚠️ Case 2 — Minor Internal Config Fix

docker exec-it <container_name>bash

Example:

echo"ServerName localhost" >> /usr/local/apache2/conf/httpd.conf

✔ Useful for:

❗ Not persistent (lost if container is removed)

# ❌ When You MUST Recreate Container

🚫 Cannot Fix Without Removing

👉 Docker limitation: these settings are immutable after creation

🔥 Recreate Container (Correct Way)

dockerrm-f <container_name>

docker run-d \
--name nautilus \
-p8085:80 \
-v /var/www/html:/usr/local/apache2/htdocs \
  httpd

# 🧪 Validation Steps

Verify Running

dockerps

Verify Volume Mapping

docker inspect <container_name> |grep-A10 Mounts

Verify Port

ss-tulnp |grep8085

Test Website

curl http://localhost:8085/

# 🧠 Decision Guide (Important)

# 🧪 Validation Checklist

# 📌 Summary