Setting up a VPN using PPTP protocal can be vulnerable for security. Yet it is an easy and quick way to set up a virtual private network (VPN). The procedure to setup up a PPTP VPN server can be found here: https://help.ubuntu.com/community/PPTPServer The way to connect to a PPTP server on a client machine can …
Author Archives: czxttkl
Change mongodb data path to portable hard drive
Background I have a 1TB portable usb hard drive which I want to host mongodb data. The OS is ubuntu 15.04 Procedure stop your mongodb service sudo service mongod stop edit `/etc/fstab` so that the computer automatically mounts your portable drive under “mongodb” user everytime the OS boots up: UUID=018483db-1b1c-4dd2-a373-58a6aa5a10be / ext4 errors=remount-ro …
Continue reading “Change mongodb data path to portable hard drive”
Create mongodb replica sets on different machines
Important prerequisites: Confirm connectivity between machines you want to set as replica set Confirm the same version of Mongodb is installed on each machine. I tried one with mongo 2.6 and another with mongo 3.0 and totally failed. Then I installed mongo 3.0 on every machine. Don’t set authentication for all the machines before you …
Continue reading “Create mongodb replica sets on different machines”
Microsoft Word Tips
Tips again. This time is for Microsoft Word. 1. Ctrl+Shift+8 Show non-printing characters. You can also toggle it on manually in the menu. 2. Pay attention to the extension symbol in ribbon. It contains more options. Or you can see paragraph settings in Page Layout in ribbon: 3. Sometimes, you will find …
Install Latex distribution, editor and packages on Ubuntu
1. Install TexLive. This is the latex environment. https://www.tug.org/texlive/quickinstall.html We recommend to use .install-tl script to install TexLive. TexLive is usually installed at “/usr/local/texlive/year/bin/x86_64-linux/….” Although you can install vanilla TexLive via sudo apt-get install texlive, we often observe it misses advanced accessories such as fonts. 2. Install Texmaker http://www.xm1math.net/texmaker/ *** Note: On Ubuntu, Texmaker can …
Continue reading “Install Latex distribution, editor and packages on Ubuntu”
LDA Recap
It’s been half year since last time I studied LDA (Latent Dirichlet Allocation) model. I found learning something without writing them down can be frustrating when you start to review them after some while. Sometimes it is a bit embarrassing that you feel you didn’t learn that at all. Back to the topic, this post …
Collection of statistical hypothesis tests
This post is a collection of hypothesis test methodologies. The full collection is listed here: http://www.biostathandbook.com/testchoice.html. My post just goes over several hypothesis tests that are relevant to my research. One-way ANOVA: http://www.biostathandbook.com/onewayanova.html If you have one measurement variable and one nominal variable, and the nominal variable separates subjects into multiple groups, you want to test …
Continue reading “Collection of statistical hypothesis tests”
Factor Analysis and PCA
I’ve been scratching my head for a day (06/24/2015) but it ended up that I am still baffled by the concept of Factor Analysis. So first of all, let me list what I’ve learned so far today. PCA and Factor Analysis can be deemed similar from the perspective that they are both dimension reduction technologies. …
Unclean uninstallation of fcitx causes login loop on Ubuntu
Whether you realize or not, fcitx, a popular input method, if not properly uninstalled, can cause the notorious login loop issue on Ubuntu (i.e., every time you type your password and enter, you get asked to type your password again on the same login window). Here is the post talking about how to fully uninstall …
Continue reading “Unclean uninstallation of fcitx causes login loop on Ubuntu”
alsamixer automatically mutes headphones and speakers
http://askubuntu.com/questions/280566/my-headphones-mute-alsamixer-when-i-plug-them-in-hp-dv6-12-04 http://askubuntu.com/questions/541847/is-there-any-way-to-save-alsamixer-settings-other-than-alsactl-store The two links above are two popular links about dealing with the auto-mute problem of alsamixer. However, the two don’t help my situation. My solution 1. Type the following command: sudo alsamixer 2. Use `RightArrow` key to navigate to right until you see “auto-mute” 3. Use `UpArrow` or `DownArrow` key to set …
Continue reading “alsamixer automatically mutes headphones and speakers”