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About Denny Zhang

DevOps/Cloud Consultant. Here I share my experience and learning for how to deliver and maintain a complex cloud system Smoothly and Economically. In my spare time, I'm deeply addicted to Efficiency Improvement and all new open source technologies. At last, I'm a diehard Emacs veteran. Check more here.

A Complete And Easy Guide To Check Elasticsearch

To poll Elasticsearch db status, we usually need to learn and try many many REST API. When we’re new, it would take quite a while to put all the pieces together. As Ops/DevOps, we are usually more concerned about cluster health and data inside. Enclosed is A Simple Step-By-Step Guide to check elasticsearch. Cluster, Nodes, Shards, Indices, […]


Bash -e Doesn’t Exit As I expect

In bash scripting, it’s a good practice to exit for any unexpected/unhandled errors. Usually I enforce this by ‘bash -e my_script.sh’. Today just got a surprise with ‘bash -e‘. Check out below simple test. You might get bitten by this as well.


VPS Comparison: Linode VS DigitalOcean

DigitalOcean is inexpensive to AWS EC2. Surprisingly Linode is even 30%-40% cheaper than Digtialocean. Certainly Linode is much less matured to them both. But with reasonable compromise, Linode could be attracting to small business and individuals. Enclosed is a detail VPS comparison report, based on my hand-on experience.


How To Check Linux Process Deeply With Common Sense

Apparently process checking is critical. Yes, we already have tons of linux tools and tips available. Getting familiar with your weapons is actually the first step, and the easiest part. More importantly, what questions you ask, what for, when approaching your critical process. Fortunately even with plain common sense, we can dig out lots of valuable information.


15 Open Questions For DevOps Interview

Never Turn DevOps Interview Into Quiz. Find people who are positive and happy, with a focus on self-improvement, who have gratitude, are humble and comfortable with extreme transparency. Here are some handy guidelines and open questions!


9 Useful Tips For Linux Server Security

Any serious systems can’t ignore server security, especially in public Cloud. No doubt there’re tons of tips and tutorials available on the Internet. Let’s focus on fundamental and general best practices first. A List Of Security Improvements I Enforce After OS Provisioning.


9 Key Feedbacks For Prod Envs Maintenance

To break silos and improve availability, DevOps/Ops should be actively collecting useful feedback of prod env maintenance on a regular basis. Enable developers to easily access it and improve feedback loop together as a team effort. The very first and most important part. What To Examine, Providing Developers Meaningful Feedback?


Check Shell Output Without Stdout/Stderr Compromised

Ever need to check the output of shell functions/scripts? If no fatal/error messages found, resume normal procedure. Otherwise, go to error handling. Usually people solve this, by redirecting stdout/stderr to grep command. But What About Time-consuming Functions/Scripts? Say several minutes. During this period, end users are blinded with nothing printed. It could be confusing and scaring to […]


Effectively Technical Writing In GitHub

Delivering short and precise documents quickly is a key asset for DevOps. Nowdays, hosting code in GitHub is not only fancy but also overwhelming. Consequently more and more documentation effort goes to GitHub. As a late fanboy of Atlassian Confluence, I also make my preference in GitHub wiki now. Enclosed are tips for how to do […]


Docker Run Out Of Disk

We have changed daily CI tests from VM to Docker, ever since early last year. It is just awesome! Way too fast and cost-effective. But one annoying thing keeps dragging us slow. The Docker daemon server runs into low disk capacity quite often.