Mac El Capitan: Camera Not Working

Since updated to El Capitan, many things went wrong. Last time screen was blurry, now camera does not work. The symptom is camera is not recognized in FaceTime, in QuickTime Video recording, and in any video recorder app.

So a little search online gives the solution: Continue reading Mac El Capitan: Camera Not Working

Mac El Capitan: Blurry Display Issue

Recently I updated my MacBook Pro to El Captain, and I don't like El Captain. One major thing I noticed is the screen went blurry. Text and everything. My Mac does not have retina display, and yet it looked fine when I still had Yosemite. Well, not saying Yosemite was good either, but it was at least better than El Captain. Found several solutions online but they didn't quite work for me. After digging into the settings, I found below method working for me to fix the blurry issue.

Continue reading Mac El Capitan: Blurry Display Issue

Setting Up SSL Certificate for Website

04/13/2017 Update: StartSSL's certificate is currently distrusted by Chrome and Firefox. So avoid using it! Instead use Let's Encrypt (tutorial here to switch to them).

This is a simple log in case I forget the steps, it may or may not help you. A good thing about StartSSL is now they support up to 5 subdomains under the same root domain for free. This is very nice.

  1. Go to and "Authenticate" using a stored certificate. If you don't have one, you need to "Sign-Up"
  2. After logging in, first we need to validate domain. Go to "Validations Wizard" and select "Domain Validation (for SSL certificate)." Next enter your root domain, for example, Before going to the next step, if you have set domain privacy, you need to temporarily disable that to quickly get the validation code to your real email address. Procedure afterwards is trivial: enter code for validation and then re-enable domain privacy when validation completes.
  3. Download the zip, in my case If it does not automatically download, goto "Toolbox" and then "Certificate list" to retrieve the zip.
  4. Since my server is using Apache, unzip the "" in the downloaded zip and you will get two files: 1_root_bundle.crt and
  5. Enable SSL for the website by modifying the config file in apache folder. For example:

Continue reading Setting Up SSL Certificate for Website

The Way to Update A Small RAM VPS

So I have a VPS with about 700MB RAM but the available is < 100MB. Today when I do

yum update

I got the error saying

xxxx: [Errno 5] [Errno 12] Cannot allocate memory

So I solved this by update everything one by one using the following command: Continue reading The Way to Update A Small RAM VPS

Project Fi Phone Number Tip

This is a tip for people who don't care about $3.

I got the Project Fi sim card a while ago, but I got a very stupid number that I don't like. So I figured, since we could port our number to Project Fi, we should be able to find us a good number somewhere, and then port the good number to the Project Fi account. Continue reading Project Fi Phone Number Tip

Brief Review about Protocol Security

There are many application-level protocols in networks. There are File Transfer Protocols like ftp, scp, and sftp. There are Mail Protocols like smtp, pop, and imap. There are Web Protocols like http 1.0, 1.1, and 2.0. And there are many more. But they are not that secure. Continue reading Brief Review about Protocol Security