Lab Information
Task 1
The Nautilus team wants to create a debug container on Application Server 1. However, they had some specific requirements related to the CMD. Please complete the task as per details given below:
a. On Application Server 1 create a container named debug_1 using image ubuntu/apache2:latest.
b. Overwrite the default CMD with command sleep 1000.
c. Make sure the container is in running state.
Task 2
The Nautilus DevOps team is testing some applications deployment on some of the application servers. They need to deploy a nginx container on Application Server 1. Please complete the task as per details given below:
On Application Server 1 create a container named nginx_1 using image nginx with alpine tag and make sure container is in running state.
Task 3
We received a request to copy some of the data from one of the docker containers to the docker host. The container is running on App Server 1 in Stratos Datacenter. Below are more details about the task:
On App Server 1 in Stratos Datacenter copy an encrypted file /tmp/test.txt.gpg from development_3 docker container to the docker host in /tmp location. Please do not try to modify this file in any way.
Task 4
The Nautilus DevOps team has some confidential data present on App Server 1 in Stratos Datacenter. There is a container ubuntu_latest running on the same server. We received a request to copy some of the data from the docker host to the container. Below are more details about the task:
On App Server 1 in Stratos Datacenter copy an encrypted file /tmp/nautilus.txt.gpg from docker host to ubuntu_latest container (running on same server) in /tmp/ location (create this location if doesn't exit). Please do not try to modify this file in any way.
Task 5
The Nautilus DevOps team wanted to transfer some docker images from one server to another server so they wanted to save some docker images as tar archives on the docker host itself. Find below the exact requirements:
There is a docker image named nginx:mainline-alpine-slim on App Server 1 in Stratos Datacenter, save this image as nginx.tar archive under /home directory on the same server.
Task 6
We need some docker images on Application Server 1, these images will be used to create some containers later. Pull below mentioned images on Application Server 1 in Stratos DC.
a. redis:alpine
b. memcached:alpine
Task 7
The Nautilus DevOps team is planning to setup/create some docker containers on App Server 1 in Stratos Datacenter, some prerequisites are needs to be done on this server. Find below more details:
Create a new network named mysql-network using the bridge driver. Allocate subnet 182.18.0.0/24, configure Gateway 182.18.0.1.
Task 8
The Nautilus DevOps team is planning to do some cleanup on App Server 1 in Stratos Datacenter, some old and unused docker networks need to be deleted. Find below more details:
Delete a docker network named php-network from App Server 1 in Stratos Datacenter.
Task 9
There were some containers created by the DevOps team on App Server 1 in Stratos DC, and those were running fine till yesterday. Team found that those containers were exited somehow today, look into the issue and make sure all containers are in running state. Below is the name of two containers which were exited:
a. lab1_container
b. lab2_container
Lab Solutions
Task 1
✅ Part 1: Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🐳 Step 1: Create container with overridden CMD
docker run -d --name debug_1 ubuntu/apache2:latest sleep 1000
🔍 Step 2: Verify container is running (MANDATORY)
docker ps
Expected output should show:
thor@jumphost ~$ ssh tony@stapp01
The authenticity of host 'stapp01 (172.16.238.10)' can't be established.
ED25519 key fingerprint is SHA256:sOUF6DvJzgDPmWfxbZ93dLywVTVpJlPBIYjkl1ehN+c.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'stapp01' (ED25519) to the list of known hosts.
tony@stapp01's password:
[tony@stapp01 ~]$ docker run -d --name debug_1 ubuntu/apache2:latest sleep 1000
Unable to find image 'ubuntu/apache2:latest' locally
latest: Pulling from ubuntu/apache2
bf1561367389: Pull complete
c7e8d27e04b0: Pull complete
8a4d5fdfb6a1: Pull complete
Digest: sha256:bd68b3b35b01aacb11148ad9073c538a6cf59e5bc1dbfc9fe03b2f8212cbd963
Status: Downloaded newer image for ubuntu/apache2:latest
3b8556204442da606bf15d44b7cddb257863cb33fdc2e08d4624f58d4bb1f6fc
[tony@stapp01 ~]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3b8556204442 ubuntu/apache2:latest "sleep 1000" 6 seconds ago Up 2 seconds 80/tcp debug_1
⚠️ Common Lab Mistakes to Avoid
❌ Forgetting -d (container exits immediately)
❌ Misspelling container name
❌ Using --cmd (not valid)
❌ Forgetting to override command
❌ Creating container but not running
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
Normally:
docker run ubuntu/apache2:latest
The container runs Apache’s default CMD.
But the lab requires:
Replace default CMD with sleep 1000
So instead of running Apache,
the container will:
Do nothing… just sleep for 1000 seconds
This keeps the container alive for debugging.
🔍 Command Breakdown
docker run -d --name debug_1 ubuntu/apache2:latest sleep 1000
docker run → create + start container
-d → run in background
--name debug_1 → exact lab-required name
ubuntu/apache2:latest → image
sleep 1000 → overrides default CMD
🧠 Why This Keeps Container Running
If we don’t override CMD:
Apache may exit
Container may stop
Lab validation fails
But sleep 1000:
Runs for 1000 seconds
Keeps container state = Up
🧠 Exam Memory Hook
Override CMD = add command at end of docker run
Always verify with:
docker ps
Task 2
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🔎 Step 1: Check if container already exists
docker ps -a
🚀 Step 2: If container does NOT exist, create it
docker run -d --name nginx_1 nginx:alpine
🔍 Step 3: Verify (MANDATORY)
docker ps
Expected:
[tony@stapp01 ~]$ ssh tony@stapp01
The authenticity of host 'stapp01 (172.16.238.10)' can't be established.
ED25519 key fingerprint is SHA256:sOUF6DvJzgDPmWfxbZ93dLywVTVpJlPBIYjkl1ehN+c.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'stapp01' (ED25519) to the list of known hosts.
tony@stapp01's password:
Last login: Sun Feb 15 14:39:43 2026 from 172.16.238.3
[tony@stapp01 ~]$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3b8556204442 ubuntu/apache2:latest "sleep 1000" 2 minutes ago Up 2 minutes 80/tcp debug_1
[tony@stapp01 ~]$ docker run -d --name nginx_1 nginx:alpine
Unable to find image 'nginx:alpine' locally
alpine: Pulling from library/nginx
589002ba0eae: Pull complete
bca5d04786e1: Pull complete
3e2c181db1b0: Pull complete
6b7b6c7061b7: Pull complete
399d0898a94e: Pull complete
955a8478f9ac: Pull complete
6d397a54a185: Pull complete
5e7756927bef: Pull complete
Digest: sha256:1d13701a5f9f3fb01aaa88cef2344d65b6b5bf6b7d9fa4cf0dca557a8d7702ba
Status: Downloaded newer image for nginx:alpine
3302dbc559d1de00b581dcdef7cc9e4f0763b65d43fe56eb50b9dee10660474a
[tony@stapp01 ~]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3302dbc559d1 nginx:alpine "/docker-entrypoint.…" 7 seconds ago Up 5 seconds 80/tcp nginx_1
3b8556204442 ubuntu/apache2:latest "sleep 1000" 3 minutes ago Up 3 minutes 80/tcp debug_1
⚠️ Common Lab Mistakes to Avoid
❌ Using nginx:latest instead of nginx:alpine
❌ Forgetting -d
❌ Running on wrong server
❌ Creating duplicate container name
❌ Container created but exited
🧠 Part 2: Beginner-Friendly Explanation
🪜 What’s Happening?
We are:
Creating a container
Using a lightweight nginx version (alpine)
Making sure it stays running
🔍 Command Breakdown
docker run -d --name nginx_1 nginx:alpine
docker run → create + start
-d → run in background
--name nginx_1 → exact lab-required name
nginx:alpine → small nginx image
🧠 Why Alpine?
alpine version:
Smaller size
Faster pull
Common in KodeKloud labs
🧠 Exam Memory Hook
Check first → Create if needed → Verify running
Always confirm:
docker ps
Task 3
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
📂 Step 1: Copy file from container to host
docker cp development_3:/tmp/test.txt.gpg /tmp/
🔍 Step 2: Verify on host (MANDATORY)
ls -l /tmp/test.txt.gpg
Expected:
[tony@stapp01 ~]$ ssh tony@stapp01
tony@stapp01's password:
Last login: Sun Feb 15 14:42:24 2026 from 172.16.238.10
[tony@stapp01 ~]$ docker cp development_3:/tmp/test.txt.gpg /tmp/
Successfully copied 2.05kB to /tmp/
[tony@stapp01 ~]$ ls -l /tmp/test.txt.gpg
-rw-r--r-- 1 tony tony 98 Feb 15 14:44 /tmp/test.txt.gpg
⚠️ Common Lab Mistakes to Avoid
❌ Copying in wrong direction
❌ Using scp
❌ Typo in container name
❌ Modifying file after copy
❌ Forgetting /tmp/ trailing slash
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
We are copying:
Container → Host
Docker provides a built-in safe command:
docker cp
This copies the file byte-for-byte without modification.
🔍 Command Breakdown
docker cp development_3:/tmp/test.txt.gpg /tmp/
docker cp → copy between container and host
development_3: → container name
/tmp/test.txt.gpg → file inside container
/tmp/ → destination on host
🧠 Important Concept
docker cp works like a secure bridge:
Container filesystem ⇄ Docker Engine ⇄ Host filesystem
No editing. No decrypting. Just copying.
🧠 Exam Memory Hook
Host → Container → prefix with container:
Container → Host → prefix source with container:
Task 4
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🔎 Step 1: Ensure container is running
docker ps
Make sure ubuntu_latest is listed.
📁 Step 2: Ensure /tmp exists inside container
docker exec ubuntu_latest mkdir -p /tmp
(-p ensures no error if it already exists.)
📂 Step 3: Copy file from host to container
docker cp /tmp/nautilus.txt.gpg ubuntu_latest:/tmp/
🔍 Step 4: Verify inside container (MANDATORY)
docker exec ubuntu_latest ls -l /tmp/nautilus.txt.gpg
Output
[tony@stapp01 ~]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5c3732c9f4df ubuntu/apache2:latest "apache2-foreground" 2 minutes ago Up 2 minutes 80/tcp ubuntu_latest
4e06e1a6be5f httpd:alpine "httpd-foreground" 5 minutes ago Up 5 minutes 80/tcp development_3
3302dbc559d1 nginx:alpine "/docker-entrypoint.…" 6 minutes ago Up 6 minutes 80/tcp nginx_1
3b8556204442 ubuntu/apache2:latest "sleep 1000" 9 minutes ago Up 9 minutes 80/tcp debug_1
[tony@stapp01 ~]$ docker exec ubuntu_latest mkdir -p /tmp
[tony@stapp01 ~]$ docker cp /tmp/nautilus.txt.gpg ubuntu_latest:/tmp/
Successfully copied 2.05kB to ubuntu_latest:/tmp/
[tony@stapp01 ~]$ docker exec ubuntu_latest ls -l /tmp/nautilus.txt.gpg
-rw-r--r-- 1 root root 105 Feb 15 14:47 /tmp/nautilus.txt.gpg
⚠️ Common Lab Mistakes to Avoid
❌ Copying in wrong direction
❌ Forgetting to create /tmp if missing
❌ Using wrong container name
❌ Editing file after copying
❌ Running command on wrong server
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
We are moving a file:
Docker Host → Running Container
Docker provides a direct tool for this:
docker cp
It copies the file exactly as-is.
🔍 Command Breakdown
docker cp /tmp/nautilus.txt.gpg ubuntu_latest:/tmp/
/tmp/nautilus.txt.gpg → source on host
ubuntu_latest: → target container
/tmp/ → destination inside container
🧠 Why Create /tmp First?
If directory does not exist:
Docker copy may fail
Lab validation may fail
So we use:
mkdir -p
Safe even if directory already exists.
🧠 Exam Memory Hook
Host → Container
Prefix destination with container name.
Task 5
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🔎 Step 1: Confirm image exists
docker images | grep nginx
Ensure you see:
nginx mainline-alpine-slim
💾 Step 2: Save image as tar archive
sudo docker save nginx:mainline-alpine-slim -o /home/nginx.tar
🔍 Step 3: Verify archive creation (MANDATORY)
ls -lh /home/nginx.tar
Output
[tony@stapp01 ~]$ docker images | grep nginx
nginx alpine b76de378d572 10 days ago 62.1MB
nginx mainline-alpine-slim a68d27696acb 10 days ago 12.7MB
[tony@stapp01 ~]$ docker save nginx:mainline-alpine-slim -o /home/nginx.tar
open /home/.docker_temp_2172181232: permission denied
[tony@stapp01 ~]$ sudo docker save nginx:mainline-alpine-slim -o /home/nginx.tar
We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:
#1) Respect the privacy of others.
#2) Think before you type.
#3) With great power comes great responsibility.
[sudo] password for tony:
[tony@stapp01 ~]$ sudo docker save nginx:mainline-alpine-slim -o /home/nginx.tar
[tony@stapp01 ~]$ ls -lh /home/nginx.tar
-rw------- 1 root root 13M Feb 15 14:53 /home/nginx.tar
⚠️ Common Lab Mistakes to Avoid
❌ Using docker export instead of docker save
❌ Wrong image tag
❌ Saving in wrong directory
❌ Typo in filename
❌ Running on wrong server
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
We are converting a Docker image into a portable archive file.
Think of it like:
Docker Image → .tar file
This allows:
Transfer to another server
Backup
Offline loading
🔍 Command Breakdown
docker save nginx:mainline-alpine-slim -o /home/nginx.tar
docker save → saves an image
nginx:mainline-alpine-slim → exact image name + tag
-o → output file
/home/nginx.tar → destination path
🧠 Important Concept
docker save vs docker export
Command Used For
docker save Save entire image (correct here)
docker export Export container filesystem (wrong for this lab)
For transferring images → always use docker save
🧠 Exam Memory Hook
Image backup = docker save
Container filesystem backup = docker export
Task 6
✅ Part 1: Lab Guidelines (Exam-Safe Mode)
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
📥 Step 1: Pull redis image
docker pull redis:alpine
📥 Step 2: Pull memcached image
docker pull memcached:alpine
🔍 Step 3: Verify images (MANDATORY)
docker images | grep alpine
Output
[tony@stapp01 ~]$ docker pull redis:alpine
alpine: Pulling from library/redis
589002ba0eae: Already exists
23739fb30465: Pull complete
580cc54ee1be: Pull complete
0adf826af742: Pull complete
7586fb43755e: Pull complete
4f4fb700ef54: Pull complete
3bce66bdaf29: Pull complete
Digest: sha256:fd83658b0e40e2164617d262f13c02ca9ee9e1e6b276fd2fa06617e09bd5c780
Status: Downloaded newer image for redis:alpine
docker.io/library/redis:alpine
[tony@stapp01 ~]$ docker pull memcached:alpine
alpine: Pulling from library/memcached
589002ba0eae: Already exists
a3e0ee508166: Pull complete
15bf9562ecbc: Pull complete
e24c6974a0da: Pull complete
e7a859de0eb0: Pull complete
5c7be89a9ef6: Pull complete
Digest: sha256:8a82a3927694e42bc52679dc81532244de51e5faed5f9541a1283e3ad7271db1
Status: Downloaded newer image for memcached:alpine
docker.io/library/memcached:alpine
[tony@stapp01 ~]$ docker images | grep alpine
redis alpine 060b91c4b1ee 4 days ago 97.2MB
nginx alpine b76de378d572 10 days ago 62.1MB
nginx mainline-alpine-slim a68d27696acb 10 days ago 12.7MB
memcached alpine 7977390ffe9a 2 weeks ago 13MB
httpd alpine df4281218506 2 weeks ago 67.1MB
⚠️ Common Lab Mistakes to Avoid
❌ Pulling on wrong server
❌ Forgetting tag :alpine
❌ Typo in image name
❌ Using docker run instead of docker pull
❌ Not verifying after pull
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
We are downloading Docker images from Docker Hub to the local server.
Think of it like:
Docker Hub → App Server 1
These images will later be used to create containers.
🔍 Command Breakdown
docker pull redis:alpine
docker pull → download image
redis → image name
alpine → lightweight tag version
Same logic applies to:
docker pull memcached:alpine
🧠 Why Use Alpine?
alpine images:
Smaller size
Faster downloads
Common in exam labs
🧠 Exam Memory Hook
Need image only? → docker pull
Need container? → docker run
Task 7
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🌐 Step 1: Create Docker network
docker network create \
--driver bridge \
--subnet 182.18.0.0/24 \
--gateway 182.18.0.1 \
mysql-network
🔍 Step 2: Verify network creation (MANDATORY)
docker network ls
Ensure mysql-network appears.
Then inspect it:
docker network inspect mysql-network
Confirm:
Driver → bridge
Subnet → 182.18.0.0/24
Gateway → 182.18.0.1
Expected output:
[tony@stapp01 ~]$ docker network create \
--driver bridge \
--subnet 182.18.0.0/24 \
--gateway 182.18.0.1 \
mysql-network
ddfd40b6d177c0465dba049dfa5df80f37dc719bb3a0de2d2e721d871d06d09c
[tony@stapp01 ~]$ docker network ls
NETWORK ID NAME DRIVER SCOPE
e391e9569a5b bridge bridge local
cc4f2fcb3a2b host host local
ddfd40b6d177 mysql-network bridge local
4cb9e8bca69d none null local
[tony@stapp01 ~]$ docker network inspect mysql-network
[
{
"Name": "mysql-network",
"Id": "ddfd40b6d177c0465dba049dfa5df80f37dc719bb3a0de2d2e721d871d06d09c",
"Created": "2026-02-15T14:58:00.548317629Z",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "182.18.0.0/24",
"Gateway": "182.18.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {},
"Labels": {}
}
]
⚠️ Common Lab Mistakes to Avoid
❌ Typo in network name
❌ Forgetting --driver bridge
❌ Wrong subnet mask
❌ Wrong gateway
❌ Creating on wrong server
❌ Using docker network add (invalid)
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
We are creating a custom Docker network.
Normally Docker creates networks automatically, but here we need:
Custom IP range
Custom gateway
Specific name
🔍 Command Breakdown
docker network create
→ Creates new network
--driver bridge
→ Standard Docker local network driver
--subnet 182.18.0.0/24
→ Defines IP range (256 addresses)
--gateway 182.18.0.1
→ Default route for containers
mysql-network
→ Network name required by lab
🧠 Why This Matters
Later, containers attached to this network will get IPs like:
182.18.0.x
This allows:
Controlled communication
IP planning
Multi-container architecture
🧠 Exam Memory Hook
Custom network = docker network create
Always define: driver → subnet → gateway → name
Task 8
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🔎 Step 1: Verify network exists
docker network ls
Ensure php-network appears in the list.
🗑 Step 2: Remove the network
docker network rm php-network
🔍 Step 3: Verify deletion (MANDATORY)
docker network ls
php-network should no longer appear.
Output
[tony@stapp01 ~]$ docker network ls
NETWORK ID NAME DRIVER SCOPE
e391e9569a5b bridge bridge local
cc4f2fcb3a2b host host local
ddfd40b6d177 mysql-network bridge local
4cb9e8bca69d none null local
5e7aef91b1bc php-network bridge local
[tony@stapp01 ~]$ docker network rm php-network
php-network
[tony@stapp01 ~]$ docker network ls
NETWORK ID NAME DRIVER SCOPE
e391e9569a5b bridge bridge local
cc4f2fcb3a2b host host local
ddfd40b6d177 mysql-network bridge local
4cb9e8bca69d none null local
⚠️ Common Lab Mistakes to Avoid
❌ Running command on wrong server
❌ Typo in network name
❌ Trying to use docker rm instead of docker network rm
❌ Not verifying after deletion
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Are We Doing?
Docker networks are like private switches connecting containers.
Here, we are simply deleting an unused one.
🔍 Command Breakdown
docker network rm php-network
docker network → network management
rm → remove
php-network → exact name
🧠 Important Concept
You cannot delete a network if containers are attached to it.
Think of it like:
You can’t remove a switch while devices are still plugged in.
🧠 Exam Memory Hook
Remove container → docker rm
Remove network → docker network rm
Task 9
✅ Part 1: Lab Guidelines
🔑 Step 0: Login to App Server 1
ssh tony@stapp01
Password:
Ir0nM@n
🔎 Step 1: Check container status
docker ps -a
Look for:
lab1_container → Status: Exited
lab2_container → Status: Exited
▶️ Step 2: Start both containers
docker start lab1_container
docker start lab2_container
🔍 Step 3: Verify containers are running (MANDATORY)
docker ps
Expected:
lab1_container → Status: Up
lab2_container → Status: Up
Output
[tony@stapp01 ~]$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
aafb31e4b2e0 nginx:1-alpine3.18-slim "/docker-entrypoint.…" About a minute ago Exited (0) 59 seconds ago lab2_container
aa65e7d8c11a nginx:1-alpine3.18-slim "/docker-entrypoint.…" About a minute ago Exited (0) About a minute ago lab1_container
5c3732c9f4df ubuntu/apache2:latest "apache2-foreground" 15 minutes ago Up 15 minutes 80/tcp ubuntu_latest
4e06e1a6be5f httpd:alpine "httpd-foreground" 18 minutes ago Up 18 minutes 80/tcp development_3
3302dbc559d1 nginx:alpine "/docker-entrypoint.…" 19 minutes ago Up 19 minutes 80/tcp nginx_1
3b8556204442 ubuntu/apache2:latest "sleep 1000" 22 minutes ago Exited (0) 5 minutes ago debug_1
[tony@stapp01 ~]$ docker start lab1_container
docker start lab2_container
lab1_container
lab2_container
[tony@stapp01 ~]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
aafb31e4b2e0 nginx:1-alpine3.18-slim "/docker-entrypoint.…" About a minute ago Up 10 seconds 80/tcp lab2_container
aa65e7d8c11a nginx:1-alpine3.18-slim "/docker-entrypoint.…" About a minute ago Up 10 seconds 80/tcp lab1_container
5c3732c9f4df ubuntu/apache2:latest "apache2-foreground" 16 minutes ago Up 16 minutes 80/tcp ubuntu_latest
4e06e1a6be5f httpd:alpine "httpd-foreground" 19 minutes ago Up 19 minutes 80/tcp development_3
3302dbc559d1 nginx:alpine "/docker-entrypoint.…" 20 minutes ago Up 20 minutes 80/tcp nginx_1
⚠️ If Containers Fail to Start
Check logs:
docker logs lab1_container
docker logs lab2_container
But normally in KodeKloud labs, simple restart is enough.
⚠️ Common Lab Mistakes to Avoid
❌ Using docker run (creates new container — wrong)
❌ Removing and recreating container
❌ Forgetting to verify
❌ Running on wrong server
🧠 Part 2: Beginner-Friendly Explanation
🪜 What Happened?
Containers can exit because:
Main process stopped
System reboot
Manual stop
Crash
When a container stops, Docker shows:
Exited (code)
🔍 Why docker start Works
docker start lab1_container
This:
Restarts the existing container
Keeps all configuration intact
Does not create a new container
🧠 Important Concept
docker run → create + start new container
docker start → start existing stopped container
Here we need:
Restart existing containers only
🧠 Exam Memory Hook
Exited container? → docker start
Need new container? → docker run
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