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Knowledge Base

A journey of sys administration

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Knowledge Base

  • Knowledge Base
  • Linux
  • Linux - Firewall
  • Firewalld guide

Firewalld guide

Reference

An Introduction to Firewalld

https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-using-firewalld-on-centos-7

Quick guide

  • Ansible
    • How to bootsrap Docker with Ansible
    • How to use Ansible to install and configure native Apache
    • Ansible Dynamic Inventory
    • Ansible Conditional Checks
  • AWS
    • Mount EBS volume to EC2 Linux
    • Analyze and Reduce Cost of NAT Gateway
    • Allow all egress in CloudFormation Security Group
    • ECS \ ECR AWS Private Link
    • Swap file on Ubuntu AMI
    • CloudFront & Lambda@Edge
    • Lambda Edge redirect users based on their location
    • Host multiple websites with one S3 bucket
    • Deploying a Production grade VPC on AWS
    • Speed up ECS Deployment
    • AWS EBS Burst Behaviour in EC2 and RDS
    • Automated Postgres backup to S3
    • ECS Exec
    • Assume IAM role
    • Create SSM Endpoints
    • Rotate EC2 Key Pair
    • Store AWS Lambda Secrets
    • AWS Data Transfer Costs
    • Managing Outbound Security Groups for Bastion Host
    • ACM Create Free Public SSL Certificate
    • AWS Session Manager
    • AWS Parameter Store Secure String Permissions
    • Prevent accidental infinite loop in Lambda with API Gateway
    • API Gateway forward path downstream application
  • AWS - CloudFormation
    • CloudFormation Stack Splitting
    • Install Docker via CloudFormation
    • Install CloudWatch Agent on Ubuntu using CloudFormation
    • Validate CloudFormation Template
    • Fargate CloudFormation Example
    • Deploying a Docker Image with CloudFormation
    • Building VPC with CloudFormation
  • AWS - CloudWatch
    • Installing CloudWatch Agent
  • Bash
    • Check if variable is empty
  • CircleCI
    • Expose environment variables in CircleCI run step
    • Connect to private/internal network with VPN in CircleCI
    • Connect via SSH jump host in CircleCI
    • Connect to local PostgreSQL container without password
    • Persist environment variables across jobs and steps
    • CircleCI notifications on Google Chat
    • Only run a job on PR in CircleCI
  • Database
    • Database - MongoDB
      • Create DB for MongoDB container on startup
      • MongoDB - The importance of indexing
    • Database - MySQL
      • How to backup MySQL / MariaDB
    • Database - PostreSQL
      • PgPool memory requirements
      • Check why Postgres is not using index
      • How to automatically attach nodes to pgpool with pcp
      • How to Partially Restore a PostgreSQL Database
  • Docker
    • How to install Docker & Docker Compose (Centos / RHEL)
    • Creating Apache, MariaDB and PHP-FPM container with Docker Compose
    • Dockerfile Conditions
    • Running GUI app in Docker containers (X11)
    • Docker Buildx Caching on CI server
    • Audio in Docker Container
    • Dockerfile good practices for Node and NPM
    • Containers
    • Docker in Docker Caching in Gitlab
    • Set timezone in Docker image
    • Configure Shared Memory for Docker container
    • Docker SSL Certificates
    • Give access to Host USB for Serial device on Docker container
  • Git
    • Git always asking for credentials
    • Git unable to connect to cache daemon
    • Resolve conflict in a Pull Request
    • Rebase using SourceTree
    • Committing lock files to repo
    • Merge upstream code into forked repo using SourceTree
    • How to identify large commits in git history
    • Scan Repositories for Secrets using Gitleaks
    • Keep Secrets out of Git repositories
  • Grafana
    • Grafana Email Notification
  • Golang
    • Inject Build-time vars with Golang
  • Installation
    • Download and install RHEL8 - Free
    • How to install vCenter Server Appliance 6.0
    • How to install MongoDB on Centos
    • How to install Zabbix on Centos
    • How to install Zabbix Agent (Centos / RHEL)
    • Installing & Configuring PgPool2 (for RDS)
  • Jenkins
    • Create Jenkins job to deploy files - Publish over SSH
    • Jenkins Useful Plugins
  • Linux
    • Linux - Date & Time
      • How to check if date time is synced to NTP
      • How to Fix Time Not Synchronized on Ubuntu Server
    • Linux - CLI
      • Yum / DNF Cheat Sheet
      • How to check and list running services (Centos / RHEL)
      • Delete files older than x days
      • Creating Linux services with systemd (Centos / RHEL)
      • sed replace variable in double quotes
      • sed preview only lines that changes
      • Load environment variables from .env file in Bash
      • Force apt update from unsigned repository
    • Linux - Filesystem
      • Linux Filesystem
      • Find out largest directories and files
      • How to extend / reduce LVM
      • When does /tmp get cleared
    • Linux - Firewall
      • How to block outgoing connections on Centos / RHEL
      • Firewalld guide
    • Linux - Log Management
      • How to manage log files using logrotate
    • Linux - Network
      • How to find listening ports
      • How to set Static IP address (Centos / RHEL)
    • Linux - Security / Authentication & Authorization
      • How to edit sudoers file
      • Linux ACLs
      • How to use public key authentication with SSH
    • Linux - SMTP
      • Postfix bounce unknown user
  • NodeJS
    • Uninstall node version of nvm
    • Check installed version of npm packages
    • Clear cache of electron
    • Use clustering to improve performance
    • Solve package lock json integrity discrepancy
  • Misc - Wordpress
    • Wordpress Home URL vs Site URL
    • Reduce space between blocks in Wordpress
    • Database connection error for WordPress PHP FPM
    • Enable Debugging for Wordpres
    • Common PHP v8.1 Compatibility Fixes for Wordpress
  • Python
    • Configure Gunicorn for Docker
    • Install pyenv / virtualenv
    • Find dependency of pip package without installing
    • Using pyenv for Multiple Python versions
  • SSH
    • Run SSH commands remotely without Key Authentication
    • Use ProxyJump
    • Execute SSH commands remotely
  • SSL
    • How to generate certificate - signed by Root CA
    • How to create a private Root CA
  • Vagrant
    • Cloning private repos in Vagrant
  • YAML
    • Break string in YAML over multiple lines

Tags

acl backup centos chrony date disk dnf docker docker-compose filesystem firewall firewalld installation linux logrotate logs lvm mysql network ntp permission rhel security services space sudoers systemd time vmware volume yum zabbix
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