Problem Solving

Edit hostname on Ubuntu

Edit /etc/hostname
```
sudo nano /etc/hostname
```
Replace any hostname you like. Save the file.
/etc/hostname
```
hello-laptop
```
Reboot the system
```
sudo reboot
```
Check your hostname
```
hostname
```

Fix docker-compose ERROR: max > virtual memory areas vm.max_map_count [65530] is too low, increase to > at least [262144]

Increase VM max map count to the respective value

sudo sysctl -w vm.max_map_count=262144

Fix Git LFS Pointers issue

git lfs migrate import --no-rewrite "file_path" "file_path"
git lfs ls-files | grep "file_path"
git lfs push origin --all
git push origin --all

Basically, the first comand is to reimport back those files into pointer files in LFS, without writing the history. Do take note that you can include as many file_path as you can.

Next, the second command is to help us to check whether the file_path already been imported as Git LFS pointers files.

Lastly, we just need to push back the LFS files and the contents to the repository itself.

No Module named 'apt_pkg'

Method 1 - Install `python-apt` package

sudo apt-get install python-apt

Method 2 - Reinstall `python3-apt` package

sudo apt-get python3-apt --reinstall

Method 3 - Properly set `.so` file location

cd /usr/lib/python3/dist-packages
sudo cp apt_pkg.cpython-310-x86_64-linux-gnu.so apt_pkg.so

add-apt-repository unable to support jammy

cd /usr/lib/python3/dist-packages
sudo cp apt_pkg.cpython-310-x86_64-linux-gnu.so apt_pkg.so

Setup self-hosted GitHub runner

With self-hosted runners, you can create custom hardware configurations that meet your needs with processing power or memory to run larger jobs, install software available on your local network, and choose an operating system not offered by GitHub-hosted runners. — GitHub (opens in a new tab)

References

Go to your repository in GitHub.
In Settings > Actions > Runners, click on New self-hosted runner button.
Choose Runner Image and Architecture. Do take note that, the architecture is based on your device specifications. For my case is x64.

Download the necessary files. You can find all these commands on the same page where you select Runner Image and Architecture.

Windows Runner

# Create a folder under the drive root
mkdir actions-runner; cd actions-runner
 
# Download the latest runner installer file
Invoke-WebRequest -Uri https://github.com/actions/runner/releases/download/v2.311.0/actions-runner-win-x64-2.311.0.zip -OutFile actions-runner-win-x64-2.311.0.zip
 
# Extract the installer
Add-Type -AssemblyName System.IO.Compression.FileSystem ; [System.IO.Compression.ZipFile]::ExtractToDirectory("$PWD/actions-runner-win-x64-2.311.0.zip", "$PWD")

Linux Runner

# Create a folderr under drive root
mkdir actions-runner && cd actions-runner
 
# Download the latest runner installer file
curl -o actions-runner-linux-x64-2.311.0.tar.gz -L https://github.com/actions/runner/releases/download/v2.311.0/actions-runner-linux-x64-2.311.0.tar.gz
 
# Extract the installer
tar xzf ./actions-runner-linux-x64-2.311.0.tar.gz

Here is the output after executing all these commands.

Configure and start the runner.

Windows Runner

# Configure the runner
./config.cmd --url <github-repo-url> --token <token> --labels <lists-of-label>
 
# Start the runner
./run.cmd

Linux Runner

# Configure the runner
./config.sh --url <github-repo-url> --token <token> --labels <lists-of-label>
 
# Start the runner
./run.sh

Programmatically assign labels (opens in a new tab) to a self-hosted runner is optional. Here is the sample configuration of the runner.

Verify your runner being setup.

Using your self-hosted runner. Create a new file under .github/workflows/test.yaml.

name: Test runner
on:
   push:
jobs:
   build:
      runs-on: ["self-hosted"]
      steps:
      - name: Checkout repository
         uses: actions/checkout@v4
      - name: list directory
         run: ls

Here is the output after all the CI jobs are completed.

Optional: You can configure the self-hosted runner application as a service (opens in a new tab)

Setup k3s on Ubuntu

ℹ️

k3s Documentation (opens in a new tab)

k3s GitHub (opens in a new tab)

Install k3s as a service
```
curl -sfL https://get.k3s.io | sh -
```

Fix k3s permission denied issues

mkdir ~/.kube 2> /dev/null
export KUBECONFIG=~/.kube/config
sudo k3s kubectl config view --raw > "$KUBECONFIG"
chmod 600 "$KUBECONFIG"

More details (opens in a new tab) in fixing k3s permission denied issues.

export KUBECONFIG=~/.kube/config to either ~/.profile or ~/.bashrc to make it persist on reboot(Optional).
```
nano ~/.bashrc
source ~/.bashrc
```
Navigate to the last line
~/.bashrc
```
# last line
export KUBECONFIG=~/.kube/config
```
Test connection
```
kubectl get all
```

Run sudo command without a password

Open /etc/sudoers with visudo editor, as if straight away edit /etc/sudoers file with text editor, it won't validate the syntax.
```
sudo visudo
```

Append this line username ALL=(ALL:ALL) NOPASSWD:ALL at the end of the /etc/sudoers file

/etc/sudoers

# User privilege specification
root    ALL=(ALL:ALL) ALL
 
# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL
 
# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL
 
# See sudoers(5) for more information on "@include" directives:
 
@includedir /etc/sudoers.d
kc      ALL=(ALL:ALL) NOPASSWD:ALL

Open a new terminal window and test the command with root privileges
```
sudo apt-get update
```

Install Java with APT on Ubuntu

Documentation (opens in a new tab)

Update apt package
```
sudo apt update
```
Install JRE
```
sudo apt install default-jre
```
Verify Java installation
```
java -version
```
Install Java JDK
```
sudo apt install default-jdk
```
Verify Java JDK installation
```
javac -version
```

Install Java OpenJDK 17

Update apt package
```
sudo apt update
```

Install OpenJDK and JRE 17

sudo apt-get install openjdk-17-jdk openjdk-17-jre -y

Check Java Version
```
java -version
```

Install Maven (MVN)

Update apt package
```
sudo apt update
```
Install Maven
```
sudo apt-get install maven -y
```
Check Maven Version
```
mvn -version
```

Install latest Git

PPA Git (opens in a new tab)

Install stable Git version

sudo add-apt-repository ppa:git-core/ppa
sudo apt-get update
sudo apt-get install git

Check Git version
```
git --version
```

Install packages using deb file

Navigate to your deb file location
Install a .deb file
```
sudo dpkg -i <file-name>.deb
```

Install KubeVirt

ℹ️

KubeVirt Releases

KubeVirt Installation Documentation (opens in a new tab)

Install KubeVirt operator

export VERSION=$(curl -s https://api.github.com/repos/kubevirt/kubevirt/releases | grep tag_name | grep -v -- '-rc' | sort -r | head -1 | awk -F': ' '{print $2}' | sed 's/,//' | xargs)
echo $VERSION
kubectl create -f https://github.com/kubevirt/kubevirt/releases/download/${VERSION}/kubevirt-operator.yaml

Deploy KubeVirt Custom Resource

kubectl create -f https://github.com/kubevirt/kubevirt/releases/download/${VERSION}/kubevirt-cr.yaml

Install Virtctl

ARCH=$(uname -s | tr A-Z a-z)-$(uname -m | sed 's/x86_64/amd64/')
curl -L -o virtctl https://github.com/kubevirt/kubevirt/releases/download/${VERSION}/virtctl-${VERSION}-${ARCH}
chmod +x virtctl
sudo install virtctl /usr/local/bin

Install Jenkins with Docker Compose

Dockerhub Jenkins (opens in a new tab)

Create docker-compose.yml

docker-compose.yml

version: '3.8'
services:
  jenkins:
    image: jenkins/jenkins:jdk11
    restart: always
    privileged: true
    user: root
    ports:
      - '8081:8080'
      - '50000:5000'
    container_name: jenkins_jdk11
    volumes:
      - ~/Desktop/self-hosted/jenkins_home:/var/jenkins_home
      - /var/run/docker.sock:/var/run/docker.sock

You can map /var/jenkins_home to any local location you liked

Start docker-compose.yml as background
```
docker-compose up -d
```
Verify Jenkins container service
```
docker-compose ps
```

Get the Jenkins admin password

docker exec jenkins_jdk11 cat /var/jenkins_home/secrets/initialAdminPassword

Open your browser, navigate to localhost:8081, and paste your password

Share your local server with Ngrok

ℹ️

Ngrok

Ngrok Documentation

Sign up for Ngrok
[Optional] You can free claim 1 subdomain from Ngrok
Download ngrok packages based on your OS.

Unzip to install

tar -xvzf ngrok-v3-stable-linux-amd64.tgz

[Optional] Copy to /usr/local/bin
```
cp ngrok /usr/local/bin
```
Connect your account
```
ngrok config add-authtoken <auth-token>
```
- The auth-token saved to configuration file: /home/<username>/.config/ngrok/ngrok.yml

Start a HTTP tunnel forwarding to your local port 80

ngrok http 80
ngrok http --domain=<domain-name> 80

Go to your browser and type your domain name.

Use different Python version to setup Python virtual environment

Docs

# Linux
pip install virtualenv
virtualenv venv --python=/usr/local/bin/python
virtualenv venv --python=/usr/local/bin/python3
 
# Windows
##  Method 1 - I don't recommend to use virtualenv as it will have some missing files
pip install virtualenv
virtualenv venv -p `which python`
virtualenv venv -p `which python3`
virtual venv -p "C:\Users\karchunt\AppData\Local\Programs\Python\Python312\python.exe"
 
##  Method 2
"C:\Users\karchunt\AppData\Local\Programs\Python\Python312\python.exe" -m venv venv

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock

sudo chmod 666 /var/run/docker.sock

Nginx permission problem [nginx: [emerg] mkdir() "/var/cache/nginx/client_temp" failed (13: Permission denied)]

Reference (opens in a new tab)

This error typically occurs in alpine docker image. Since the nginx image already have a user called nginx. We will reuse it.

FROM nginx:alpine
 
RUN touch /var/run/nginx.pid \
   && chown -R nginx:nginx /var/cache/nginx /var/run/nginx.pid
 
COPY --chown=nginx:nginx <your-files> /usr/share/nginx/html
COPY --chown=nginx:nginx <your-nginx-config> /etc/nginx/conf.d/default.conf
 
USER nginx
...

Overview