regenerate ssh host key on CentOS 7

after duplicate vm image, we need to regenerate sshd's host key, here is the steps:

rm -f /etc/ssh/ssh_host_*
systemctl restart sshd.service

it will regenerate all the necessary files to avoid the host identity warnings.

Failed Flash Player Installation on Mac

Ok, today I was trying to install Flash Player on My Mac Yosemite, but follow the adobe's web instruction always resulted failed install, so I dug a little more and finally solved my problem.

open your mac terminal type following:

cat ~/Library/Logs/Adobe_ADMLogs/Adobe_GDE.log

this will output Adobe's installer log, it tells you the actual flash player installer it downloaded, try to find a line like following:

01/09/16 10:01:54:482 | [INFO] |  |  |  |  |  |  | 76833 | The file to be downloaded is http://fpdownload.adobe.com/pub/flashplayer/pdc/20.0.0.267/install_flash_player_osx.dmg

now you know where to download the file, still in the same terminal window, use wget to download the dmg file.

wget http://fpdownload.adobe.com/pub/flashplayer/pdc/20.0.0.267/install_flash_player_osx.dmg

it will download the dmg file in your current folder, most likely your home folder, now use Finder to navigate to the dmg file and launch it and click the "Install Adobe Flash Player" icon in the mounted disk image.

good luck!

Apple Watch Digital Touch Not Working?

If you are experiencing no digital touch on Apple Watch, here is the steps you can take to solve the problem:

Your partner can not get your digital touch, but can get your iMessage

• make sure he/she is in your Apple Watch's friends list
• and not in your blocked list
• now the important part: on your iPhone, go to Settings->Message, turn OFF iMessage, then wait for at least 10 seconds, then turn it back ON
• now try to send your digital touch from your Apple watch
• Get it?

How to hard reset Windows Phone 8

You will lose all data on the phone, you are warned!

1. Power off the phone. 
2. Press and hold Volume down key while connect the charger to phone. You will see a big exclamation mark on the screen. 
3. Now press these keys in sequence: Volume Up, Volume Down, Power, Volume Down. 
4. Phone will reboot and you will see rolling gears on the screen, it will take couple minutes to fully boot up. 
5. Your phone is reset to factory settings and just like a brand new phone.

Fixing Xcode the requested file was not found in any documentation set

Anyone using Xcode to program for iPhone could experiencing the error like following after update the 3.1 documentation:

"the requested file was not found in any documentation set".

after inspect the the Apple's latest iPhone OS 3.1 docset package, it looks like someone at APPLE did not run a good QA on this one. anyhow, I fixed the prompt by using following method in the exchange to get back the old version of documentation set for 3.1

the problematic docset is version v22.20.0 as you can see in the Get Info dialog in Xcode. we need go back to the old version of document. Here is how:

1. download the old docset file from apple's website, you can follow the following:
feed://developer.apple.com/rss/com.apple.adc.documentation.AppleiPhone3_1.atom
download the v21.13.0 or v21.12.0, they both point to the same file, which is version 21.13.

2. the above download is a xar file, so you need to use xar to extract it:
xar -xf com.apple.adc.documentation.AppleiPhone3_1.iPhoneLibrary.xar
this will result a directory as com.apple.adc.documentation.AppleiPhone3_1.iPhoneLibrary.docset

3. unsuscribe for the Apple iPhone OS3.1 docment in Xcode, and Reveal in Finder of the iPhone OS 3.1 Library, delete the whole com.apple.adc.documentation.AppleiPhone3_1.iPhoneLibrary.docset directory.

4. now move the directory you extracted in step 2 to the location of step 3.

5. the error message will be gone. you will see a button says "UPDATE" at the right side the iPhone OS 3.1 Library, DO NOT click on that, if you do, you will end up with the error message again.

Hope someone at APPLE fix the issue soon!!!!!!!!!!