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  Install and setup vsftpd on AWS server

When developing websites, frequently we may need to upload source codes to the remote server. To ease of thew work, many website developers set up FTPs to upload the files. This post is a tutorial on how to install and setup vsftpd on a server. vsftpd is a very popular FTP service on Unix-like systems. Open command terminal, then install the vftpd by issuing command yum install vsftpd or sudo apt-get install vsftpd After installing the vsftpd, the config file needs to be updated based on the ope...

   FTP,vsftpd,AWS,Passive,Active     2015-02-02 02:20:27

  Empty slice vs nil slice in GoLang

In Go, there is a type called slice which is built on top of array. It's a very convenient type when we want to handle a group of data. This post will explain a subtle but tricky difference between empty slice and nil slice. A nil slice is a slice has a length and capacity of zero and has no underlying array. The zero value of slice is nil. If a slice is declared like below, it is a nil slice. package main import "fmt" func main() { var a []string fmt.Println(a == nil) } The output will be t...

   GOLANG,JSON,EMPTY SLICE,NIL SLICE     2018-10-18 09:25:21

  jQuery to check whether checkbox is checked

In Vanilla JavaScript, the correct way of checking whether a checkbox is checked is to get the property checked of the checkbox. Assuming there is an checkbox with id "checkbox1", below line will return true if the checkbox is checked while it will return false if the checkbox is unchecked: document.getElementById("checkbox1").checked In jQuery, there are a few ways to check this. The first one is to using the corresponding counterpart of the Vanilla JavaScript, it is to check the checked proper...

   jQuery,checked,checkbox,attr,prop     2015-07-25 08:49:54

  Guide for installing Ubuntu in VirtualBox on Windows

Have you ever tried to have two OSs installed on your PC? Do you want to try out the new Ubuntu system? If you do want to use Ubuntu when at the same time you are using Windows, you may want to install your Ubuntu in an VirtualBox. In this post, we will show you how to install Ubuntu in VirtualBox on Windows. Pre-requisites VirtualBox -- You can download it from Oracle. Ubuntu -- You can download it from here. Please note it should be an ISO file The Ubuntu used in this post is Ubuntu 12.04 LT...

   Ubuntu,Windows,VirtualBox     2014-01-15 03:21:05

  CSS box-shadow Can Slow Down Scrolling

Working on one of the Chromebooks Google lets you borrow on Virgin America flights, I noticed scrolling down the page on my airbnb.com dashboard was much slower than on my normal laptop. I chalked it up to weak Chromebook hardware, but other sites were scrolling just fine. box-shadow had caused slow scrolling on our search results page before, so I did some investigation.I used Chrome's Timeline tab to see the duration of paint events on the page. Before each test I forced a garbage collection a...

   CSS,box-shadow,performance,Timeline,Chromebook     2011-11-13 08:13:48

  CASSANDRA data model

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable. Features of Cassandra are: Flexible schema, no need to design schema first, it's very convenient to add or delete strings Support range search on keys High usability, extensible. The single node error will not affect the cluster. We can think Cassandra's data model as a 4 or 5 dimensional Hash. COLUMN Columns is the smallest data unit in Cassandra, it is a 3 dimensional data...

   Cassandra,database,sort     2013-06-08 22:07:40

  Handle ”cannot modify header information – headers already sent by”

Man PHP developers should encounter ”Warning: Cannot modify header information – headers already sent by ….” error before when executing a PHP script. Here are some solutions to this error. 1. Blank line Check whether there is any blank line after , especially in the files which are used in include() and require(0, some problems are caused by blank lines. 2. Add exit() after head() header (“Location: xxx”); exit(); 3. Use output cache <?php ob_start(); ...

   header sent, PHP error handle     2012-11-17 08:45:22

  Fix issue docker-credential-desktop not installed or not available in PATH on Mac

Sometimes you may encounter below issue while running docker-compose on MacOS. Traceback (most recent call last): File "docker-compose", line 6, in <module> File "compose/cli/main.py", line 71, in main File "compose/cli/main.py", line 127, in perform_command File "compose/cli/main.py", line 1085, in up File "compose/cli/main.py", line 1081, in up File "compose/project.py", line 527, in up File "compose/service.py", line 354, in ensure_image_exists File "compose/service.py",...

   MACOS,DOCKER,DOCKER-COMPOSE     2020-06-23 03:25:16

  Recover deleted file in Linux EXT3 file system

Environment : CentOS 5.3 x86_64, /dev/sdb1 is the data segment /data0. EXT3 file system. Problem : /data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp is deleted mistakenly and httpcws.cpp is not backed up. It will take much time to rewrite this program again. So we must recover it back. debugfs is feasible in EXT2 file system, but in EXT3 file system, it's not very useful. There is one open source software called ext3grep which can help us recover deleted file in EXT3 file system. The recovery steps a...

   Linux,EXT3,File recovery     2013-08-16 07:06:45

  C/C++ Pointer Declaration Syntax – It makes sense!

I never really liked the way pointers are declared in C/C++: int *a, *b, *c; // a, b and c are pointers to int The reason is that I am used to reading variable declarations as MyType myVar1, myVar2, myVar3; and I always read “int*” as the type “integer pointer”. I therefore wanted the following int* a, b, c; // a is a pointer to int, b and c are ints to mean that a, b and c all were of type int*, i.e. pointers to int. and I therefore found it slightly a...

   C,Pointer,Declaration,Attempt     2012-02-22 05:43:58

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