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OtterShell Documentation

website·Indexed 30 days ago

https://ottershell.vercel.app/docs/category/tasks

A collection of technical guides and practical exercises covering system administration and DevOps tasks, including Kubernetes, Docker, Jenkins, OpenStack, Linux kernel compilation, and the configuration of LAMP/LEMP stacks, DNS (Bind9), and High Availability clusters.

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What's inside OtterShell

  1. Configure Docker Compose for a PHP application with MariaDB

    This configuration defines a two-tier architecture: a PHP application container (bookmedik) and a MariaDB database container (bn-mariadb). The application depends on the database and uses environment variables for database connectivity and application credentials.
    version: '3.3'
services:
  bn-mariadb:
    container_name: bn-mariadb
    image: mariadb
    restart: always
    environment:
      MARIADB_ROOT_PASSWORD: root
      MARIADB_DATABASE: bookmedik
      MARIADB_USER: admin
      MARIADB_PASSWORD: admin
    volumes:
      - mariadb_data:/var/lib/mysql
  bookmedik:
    container_name: bn-bookmedik
    image: belennazareth/bookmedik:v1_2
    restart: always
    environment:
      bookmedik_user: admin
      bookmedik_passwd: admin
      host_database: bn-mariadb
      db_name: bookmedik
    ports:
      - 8081:80
    depends_on:
      - bn-mariadb
volumes:
    mariadb_data:

  2. Verify and inspect Kubernetes Deployment resources

    After applying a Deployment, you can verify the status of the Deployment, the automatically created ReplicaSets, and the resulting Pods using kubectl get. Detailed information about the Deployment's state and events can be retrieved using describe.
    # List resources
kubectl get deployment
kubectl get replicaset
kubectl get pods

# Get detailed information
kubectl describe deployment test-web-deploy

  3. Design the OpenStack lab environment architecture

    The lab environment consists of four machines using a sub-domain format: tunombre.gonzalonazareno.org.

    • Machine 1 (alfa): OpenStack instance running Debian 11 Bullseye. Acts as the gateway for the internal network.
    • Machine 2 (bravo): OpenStack instance running Rocky Linux 9.
    • Machine 3 (charlie): LXC container running Ubuntu 20.04 (hosted on alfa).
    • Machine 4 (delta): LXC container running Ubuntu 20.04 (hosted on alfa).

  4. Identify CentOS migration alternatives

    Due to the end of support for CentOS 8 and the scheduled end-of-life for CentOS 7 (June 30, 2024), several alternative distributions are available for server migration:

    • Red Hat Solutions: Red Hat Enterprise Linux (RHEL), CentOS Stream.
    • Oracle Solution: Oracle Linux.
    • Community-driven/New Distributions: AlmaLinux, Rocky Linux, VZLinux, EuroLinux.
    • Other Linux Distributions: Debian, openSUSE, Slackware.

  5. Inspect package details with apt and aptitude

    Several commands can be used to retrieve information about a package regardless of whether it is installed:

    • apt show: Provides a general detailed description of the package.
    • apt-cache showpkg: Provides extensive information including reverse dependencies, versions, and descriptions.
    • aptitude show: Displays detailed information about a package candidate or installed version.
    apt show <package_name>
apt-cache showpkg <package_name>
aptitude show <package_name>

  6. Use Bind Mounts for host-to-container file sharing

    Bind mounts allow you to map a specific directory on the host machine to a directory in the container. This is useful for development as changes made to the host files are immediately reflected in the container.
    # Mount a specific host path (/home/debian/bindmount) to the container path
docker run -d --name miweb -p 8080:80 -v /home/debian/bindmount:/var/www/html php:7.4-apache

  7. Install Docker Engine on Debian for Kubernetes

    Install Docker Engine and containerd on all cluster nodes (master and workers) to serve as the container runtime.
    # Update and install prerequisites
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg

# Add Docker GPG key
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

# Add Docker repository
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/debian $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# Install Docker Engine and containerd
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

  8. Install and enable PHP-FPM on Apache2

    To configure Apache2 to use PHP-FPM, install the php-fpm package and enable the necessary proxy modules. You must disable the standard PHP module to ensure requests are handled by FPM.
    # Install PHP-FPM
sudo apt install php-fpm

# Enable proxy and environment modules
a2enmod proxy_fcgi setenvif

# Enable the PHP-FPM configuration (example for PHP 7.4)
a2enconf php7.4-fpm

# Restart Apache to apply changes
systemctl restart apache2

# Disable the standard PHP module to avoid conflicts
a2dismod php7.4
systemctl restart apache2

  9. Provision OpenStack instance using cloud-config.yaml

    Use a cloud-config.yaml file to automate the initial setup of an OpenStack instance. This configuration handles package updates, hostname/FQDN assignment, user creation with sudo privileges and SSH keys, and root password assignment.
    #cloud-config
package_update: true
package_upgrade: true

hostname: alfa
fqdn: alfa.gonzalonazareno.org

users:
  - name: nazare
    sudo: ALL=(ALL) NOPASSWD:ALL
    shell: /bin/bash
    passwd: nazare
    ssh_authorized_keys:
      - ssh-rsa AAAAB3... [key] ... nazare@ThousandSunny
  - name: profesor
    sudo: ALL=(ALL) NOPASSWD:ALL
    shell: /bin/bash
    passwd: profesor
    ssh_authorized_keys:
      - ssh-rsa AAAAB3... [key] ... jose@debian

chpasswd:
   list: |
       root:root
   expire: False

  10. Install and initialize ISC DHCP Server

    Install the isc-dhcp-server package. Note that the service will initially fail to start because it requires configuration before it can run successfully. Logs can be checked via /var/log/syslog or systemctl -u isc-dhcp-server.
    sudo apt-get install -y isc-dhcp-server

  11. Configure an iSCSI target on a Linux server using tgt

    To create an iSCSI target with a Logical Unit Number (LUN) on a Linux server, install the tgt package and define the target in the configuration file. The backing-store directive specifies the physical device to be shared as a LUN.
    # Edit /etc/tgt/targets.conf and add the target definition
# Example: <target iqn.2023-01-target1>
#     backing-store /dev/vdb
# </target>

# Restart the tgt service to apply changes
sudo systemctl restart tgt

# Verify the target and LUN creation
sudo tgtadm --mode target --op show

  12. Install and basic setup of Postfix mail server on VPS

    To set up a basic mail server on a VPS, install Postfix for mail handling and bsd-mailx for sending emails from the command line. Ensure the server has a valid MX record (e.g., mail.yourdomain.com), port 25 is open in the firewall, and a reverse DNS entry is configured.
    # Install Postfix and mail utilities
sudo apt install postfix bsd-mailx

# Verify MX record
dig MX yourdomain.com