Performance Analysis Tools

Basic Tools In 2015, Brendan Gregg posted two great articles on Netflix blog: Linux Performance Analysis in 60 seconds, and Linux Perfomrance Tools. They have great value when I was in a urgency to spot performance issues. The articles cover the essential tools for performance troubleshooting, including: Check out load averages: uptime or w Print … Read morePerformance Analysis Tools

Common local Git operations

This is a summary of concepts in common Git operations. We will discuss brach, merge, rebase, cherrypick, stash and reset. We will not discuss pull, fetch, or push. Commit, Branch and HEAD When you run “git commit”, the following happens: Git checksums each subdirectory, and stores them as a tree object (file path and name) … Read moreCommon local Git operations

Pitfalls in deployment automation

There is no doubt that organizations with lots of manual tasks should automate at least some of the IT tasks. As the automation tools such as Ansible, Puppet become mature, the skillset becomes prevalent as well. If automation is not carried out properly, they can cost the organization an arm and a leg. The ultimate … Read morePitfalls in deployment automation

Introduction to Active Directory (AD)

Workgroup, homegroup and Windows Domain A workgroup is a group of computers on the same local network. A Windows computer not joined to a domain is part of a workgroup. In a workgroup, no computer has control over any other computer and it does not require a password. Any computer can join or leave a … Read moreIntroduction to Active Directory (AD)

Set up automation with Ansible

Ansible is very flexible automation tools with many benefits. The free version is command-line based and here is an example to set it up. Environment setup Ansible 2.8 is required or some command may not work. Ansible files (including playbooks, tasks and inventory files) are all located in /home/glowing/ansible Default inventory file needs to be … Read moreSet up automation with Ansible

Redhat Firewall configuration: firewalld vs iptables

There are in general two options to deploy firewall rules, firewalld and iptables. Firewalld can be installed and executed as a systemd service, and it is supposed to replace iptables. This article describes how to configure both. Iptables involves three different services for IPv4(iptables), IPv6(ip6tables), and software bridging (ebtables). Firewalld only involves a single service … Read moreRedhat Firewall configuration: firewalld vs iptables

cron and anacron in RedHat Linux (How logrotate works)

Cron and anacron We all know cron is a job scheduler. Many admin uses crontab to manage scheduled task. It is also important to know that crontab works at different levels as well, as well as the distinction between cron and anacron. They are similar, but different, managed by different sets of files. Below is … Read morecron and anacron in RedHat Linux (How logrotate works)