Linux
Hardware and System Performance
Disks, CPU, RAM, etc
Boot, Kernel, Recovery, and Tunables
Linux Boot Process
The below image outlines the typical flow of a Linux system boot. ============================...
Troubleshooting Boot Issues & System Recovery
==================================================================================== System boot...
GRUB - Grand Unified Boot Loader
==================================================================================== GRUBs respo...
Kernel, Modules, Tunables & initrd (Initialisation RAM Disk)
Kernel ==================================================================================== Wha...
Single User Mode
==================================================================================== You might n...
FSCK
==================================================================================== FSCK (File ...
OOB Management - KVM & DRAC
==================================================================================== KVM ------...
Single User Mode
Boot the server into 'single user mode' B. Once in single user mode, we can look to initiate t...
Linux Filesystem (FHS), Storage Concepts, LVM, & Disks
Disk and filesystem management
QUICK GUIDE: Clearing Disk Space
==================================================================================== Identifying...
Quick Guide: Expanding Disks
==================================================================================== Virtual Dis...
STORAGE CONCEPTS
==================================================================================== This page d...
FHS - Filesystem Hierarchy Standard
==================================================================================== FHS as defi...
Partitions and Filesystems
==================================================================================== Partitions ...
LVM (Logical Volume Manager)
==================================================================================== LVM, or Log...
SWAP
==================================================================================== What is SWA...
Archiving and Compression
==================================================================================== gzip ==...
fstab
==================================================================================== fstab (File...
Disk Performance
==================================================================================== I/O Schedul...
System Networking
Networking configuration and commands
Networking Commands
==================================================================================== Show networ...
Network Managers
==================================================================================== Ubuntu - Ne...
DNS and Hosts Resolution
==================================================================================== DNS and Hos...
ARP
show arp cache arp -a
User Management & File Permissions
User & Group Management
==================================================================================== Adding User...
User/Group/Password Files
==================================================================================== /etc/passwd...
Admin Privileges
User & group privileges ------------------------------------------------------------------------...
File Permissions & Ownership
==================================================================================== Linux File ...
Software & Service Management
Package Managers
==================================================================================== YUM (Yellow...
Compiling from source
Compiling an application from source essentially means that you are manually creating a package u...
Auto Restart Services
https://www.redhat.com/sysadmin/systemd-automate-recovery 1) Edit elasticsearch service unit ...
Sandboxing & CHROOT
==================================================================================== CHROOT (Cha...
Linux System Variables
Date, time, language
SSH & Authentication
All things SSH and authentication.
PAM
Pluggable Authentication Modules (PAM) PAM is essentially an authentication system that allows f...
Clearing Command Line History
Oh dear, you've made a mistake on a clients server and want to hide the evidence... There's a fe...
SSH Configuration
==================================================================================== What is SSH...
LDAP (Lightweight Directory Access Protocol)
LDAP (Lightweight Directory Access Protocol) is a protocol used to access and manage directory se...
File Transfers, Synchronisation & Shared Storage
Unison, NFS, rSync, SCP
Unison
==================================================================================== What is Uni...
NFS
NFS (Guidance based on RHEL/CentOS 7, packages and commands may differ depending on OS) =======...
rSync
==================================================================================== What is rSy...
FTP Troubleshooting
==================================================================================== FTP Passive...
vSFTPd
vsftpd (Very Secure FTP Daemon) is a popular FTP server for Linux systems. To use vSFTPd, you'll ...
Monitoring
Monitoring info and scripts
Nick Abbots Script
Nick Abbots Script: vi ukfastmon;chmod u+x ukfastmon; ./ukfastmon; rm -f ukfastmon #!/bin/bash ...
One-liners
==================================================================================== Common Erro...
Bots/Crawlers & Control/Mitigation
==================================================================================== Robots.txt ...
Resource usage and performance
==================================================================================== ATOP =====...
xmlrpc & wp-login
==================================================================================== XMLRPC Ide...
ANS IPs
-------------------------------------------------------------------------------------------------...
Useful Online Tools
https://ping.pe/
MySQL
MySQL Optimisation, Performance, and Logging
==================================================================================== MySQL Optim...
Corruption and Repairs
==================================================================================== MySQL Check...
User and Database Management
Command syntax will vary between MySQL Versions ================================================...
Binary Logging
==================================================================================== Binary Logg...
Database Monitoring (New Relic)
==================================================================================== What is New...
MySQL Encryption
Encryption Types in MySQL Data-at-Rest Encryption: Tablespace Encryption: Encrypts the en...
MySQL Remote Access
==================================================================================== To configur...
Storage Engines
MySQL supports multiple storage engines, with InnoDB and MyISAM being the most commonly used. --...
MySQL Replication
MySQL replication is a process that allows data from one MySQL database server (the primary or so...
XtraBackup
MySQL Backups - mysqldump and xtrabackup
=================================================================================== Percona Xtra...
CloudFlare
Backups & Restores
Full Server Restore (Dedi or Virtual)
Full Server Restores ===========================================================================...
Commvault Backups
==================================================================================== Installing ...
Bacula Restores
Useful Bacula commands Watch restore job: watch -n1 'echo "status client client=\"srv-IP_IP_IP...
Commvault Restores
Commvault Restores Commvault restore types: MySQL Restores File level restores VPC Restores ...
Permissions Restores
==================================================================================== Client chow...
Bacula Bextract
Bextract 1. Get list of volumes from TechDB To get an idea of what files you'll need, you need ...
Bacula Backups
==================================================================================== Backup Serv...
Mail configuration and troubleshooting
SPF, DMARC, and DKIM
SPF (Sender Policy Framework) is an email authentication record, which is essentially used to def...
Plesk Mail
-------------------------------------------------------------------------------------------------...
MTA & MDA
Mail Transfer Agent (MTA): This is responsible for sending and receiving emails between different...
QUICK GUIDE: Mail Troubleshooting
LoadBalancers
LBv1 & LBv2
Magento
Cluster
Cluster configuration, theory, and troubleshooting.
Pacemaker
Pacemaker provides a framework to manage the availability of resources. It's essentially the core...
Explanation
PCS (Pacemaker) Cluster Services: PCS (Pacemaker) Pacemaker provides a framework to manage the...
DRBD
DRBD is the service used for synchronisation of data (usually web and database files) on a cluste...
Unison
Clusters use unison, usually for synchronisation of configuration files.
NGINX
General NGINX configuration
APACHE
Logging
Server log configuration and management
WordPress
Useful WordPress-related topics
WP-CLI
==================================================================================== WP-CLI Inst...
Changing WordPress Admin Password
The WordPress admin password can be changed via the WordPress database directly, or via WP-CLI: ...
WordPress Debug Mode
==================================================================================== WordPress D...
Bash
Command man pages.
SSL
SSL validation, installation, and verification
SSL Validation
==================================================================================== SSL Validat...
SSL Checks
==================================================================================== Online Tool...
Self Signed & Free Certificates
==================================================================================== What are se...
cPanel
General cPanel-related topics
PHP
Installation, upgrades, configuration
Containerisation & Automation
Docker, Kubernetes, Ansible
What is a container?
A container is essentially an isolated (from the rest of the OS) environment that's dedicated to ...
General Docker Information
==================================================================================== To preface ...
Docker Compose
==================================================================================== Installatio...
Kubernetes (K8s)
Kubernetes - K8s Developed by Google, Kubernetes is an enterprise container management system, o...
What is automation?
Automation software is software that can be used to automate tasks - such as server configuration...
Ansible
What is Ansible? Ansible is an agentless automation system developed by RedHat, designed for dep...
GIT - Version Control
What is GIT? Git is a free and open-source distributed version control system (DVCS) widely used...
Vulnerabilities, Patching, and Security
SELinux, AppArmor, CVE
SELinux (Security Enhanced)
==================================================================================== What is SEL...
AppArmor
==================================================================================== AppArmor is...
CVE Vulnerabilities
Common Vulnerabilities and Exposures (CVE) is a system that provides a reference-method for publi...
Rootkit Scans
A rootkit is a collection of software tools that enable an attacker to gain root or administrativ...
Malware Scans
==================================================================================== ClamAV Cla...
Linux Firewalls
UFW, IPTables, Firewalld