Comparing ALIAS and CNAME Records

There are 4 types of DNS records, namely: A, CNAME, ALIAS, and URL.

The A record, maps a name to one or more IP addresses.

The URL record, redirects to the target link using http 301.

So far so good.

The CNAME record, maps a name to another name.

The ALIAS record, maps a name to another name.

Um… what??? ALIAS and CNAME look quite the same, don’t they? So when to use what?

It turns out for ALIAS, the recursive lookup will happen at the server side, so that will speed things up a lot. Also the final output is an IP, so that acts the same as an A record. Whereas for CNAME, you need to do recursive client calls to resolve all the way to the A record, then one more lookup to get the IP. That could take longer.

But the disadvantage of using ALIAS is that, the routers don’t have your geographical info, so may end up giving you sub-optimal results, i.e. An IP that’s far away from your location, but closest to your authoritative DNS server.


California Earthquake




Since when the commercials became so anime now?

How to remove iCloud Account on iOS9 / iOS8

When you forget your icloud password, and if you have the Find my iPhone feature turned on, there is practically no way to log out. The icloud password prompt will keep popping up from time to time to render your iphone/ipad useless.

There is actually a way to remove that icloud username on your device, but it requires jail-breaking. If you are determined then here are the steps.

Jailbreak your device by following this: You can get Cydia Impactor here.

Follow these steps: At step 3, the iFile app doesn’t quite work, try to download FileBrowser instead.

Once your clear out the icloud username, those annoying pop up will stopping coming. Now, make sure you get a new iCloud login and write down the password somewhere.

-bash: /bin/rm: Argument list too long

I accidentally created more than 50K empty files in a folder. When I tried to remove them using rm -rf *.tmp, I got the error -bash: /bin/rm: Argument list too long.

It turns out bash tries to expand the * into a full list, but that list became too long.

Here is how to delete that many files:

find . -name '*.tmp' | xargs rm


Why do flight times differ between traveling East vs traveling West?

I often notice that when I fly from America to China, then fly back. It’s off by an hour or two. Earth rotation shouldn’t be the reason unless we get out to the space. I did some research and it turns out it’s the wind. Make sense.


/usr/local/Homebrew/Library/Homebrew/brew.rb:12:in `’: Homebrew must be run under Ruby 2.3! You’re running 2.0.0. (RuntimeError)

brew update
brew install ruby