Resume and bio of the author Couple of articles related to my hobby - robotics
My impressions about immigration to Australia. In Russian only. Recipes for everyday problems solving
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Andrey Mikhalchuk’s Blog

Technoblog about life

Feb 18, 2015 How to quickly check if an internet store is a scam

So imagine you go to google shopping ( and search for an item to buy and google returns you a really awesome price for the thing you dreamed about your whole life (or just the last 5 minutes). And you are almost ready to go ahead and order the item from this company (because google found it for you and google is awesome). STOP! Let’s first check the background of this company.

Aug 16, 2014 Fixing MacBook Pro BootCamp Black Screen of Death

So one day I’ve power on Windows on a BootCamp-enabled Windows 7 MBP Retina and after booting and making bunch of happy sounds the display went blank. No matter how many times I rebooted it the display kept looking dead. The computer was obviously running. It’s easy to check by pressing caps lock – the small LED on that button changes its status it the OS is loaded. After researching the internet I found this is a very famous issue with NVidia chipset and the only cure for this is replacing the mainboard. Bummer!
When almost all hope was all but lost I surrendered and in preparation for bringing it to the Apple Genius unplugged the laptop from power and … the display came back to life. Wow! My first thought was that NVidia chipset is still dead, but with power supply unplugged the laptop simply switched to the Intel chipset. But the thing is that Intel chipset can’t support retina resolution and the screen remained at its impressive 2880×1800 resolution, meaning NVidia were well and alive.
After opening some more time with the computer I found hilariously obvious reason for this bizarre behavior …

Jul 18, 2014 How to migrate ownCloud 6 from sqlite to MySQL

Those who do not know what ownCloud is probably should read about it here: This is an awesome tool that provides functionality similar to dropbox, but uses your own server to host the files. We all know about dropbox’s bad behavior like storing passwords on the server side, accessing your content when you don’t want it. Actually recently I was monitoring disk activity on a computer with dropbox installed on it and found that for some reason dropbox keeps reading files where it has not business to do. It was clearly configured to replicate files in its own folder, yet was reading all files on the disk. One way or another there are a lot of reasons to get rid of dropbox and switch to ownCloud. It’s cheaper, secure and can be used to store business or confidential information where dropbox fails to provide both security and confidentiality.

By default ownCloud uses sqlite3 to keep records of the files it stores and people like myself that decided to go forth with the default configuration get trapped with this configuration. Once you load more than couple gigs of data you will notice that it gets slower and sloooower and slo… Sometimes you might even experience complete freeze on the client side.

The solution to the problem is moving the data from sqlite to something mroe serious like MySQL. Both databases have SQL in their name so the migration should be easy. Unfortunately ownCloud doesn’t provide any means to automate this migrate. To make matters worse the dialects sqlite3 and MySQL use are a little bit different so you can’t feed sqlite3 database dump directly into MySQL. I saw multiple solutions to the problem migrating ownCloud 5, but nothing for OC6 so far. Here is how I migrated it in just a few simple commands:

Apr 11, 2014 Attaching >2Tb disks to Linux

Here is the sequence of commands to make disk space usable in Linux for disks >2Tb (so your regular fdisk won’t help you here).

Mar 20, 2014 How to silence a piezo buzzer in your microwave, alarm clock etc

Almost every time I buy a piece of electronics with some sort of alarm it always includes a super loud and mega annoying buzzer notifying about the end of cycle. Though tuning it off completely is an easy operation (just open the case and cut the wire) making it just not as loud is a more complicated task involving knowledge of electronics and some soldering skills. Fortunately there is a much simpler way to accomplish the task, sometimes not even requiring the device disassembly …

Nov 15, 2013 How to make browser offline cache retrieve new version of the page when browser is online, but keep using cache when it is offline

Offline cache is awesome! For certain things. For most regular web pages it is unfortunately not. Here is web developer’s most frequent use for the offline cache: make browser use cached version of the page when browser is offline but refresh it when it gets online. What could be simpler and more natural purpose for the OC? Well, unfortunately it wasn’t designed to work like this out of the box. Even when your browser goes online it will keep using the cached version “indefinitely” until the cache manifest is updated. So what do we do in this situation?

Nov 12, 2013 AWS EC2 ssh not responding in RHEL 6.4 AMI

I was fighting with an AWS bug today seeming just ridiculous for a system that makes ssh the only way to access the server. With no console login EC2 users are completely dependent on flawless sshd operation and Amazon team just did a really bad job preparing the RHEL 6.4 image.
So here are the symptoms: you create an image from a perfectly working system with the purpose to clone it. Then you create new instance from the AMI and it seems working fine too, you can ssh to it no problem. After a reboot or too it suddenly stops responding to ssh thought the rest of the system seems working fine (HTTP server for instance). Server logs do not show any errors. Reboots do not help and EC2 doesn’t provide console access to the server.
Here is the solution:

Nov 8, 2013 How to use large / multiline text as a field in mongodb

I’m working on a project that requires storing large multiline chunks of text in MongoDB. The chunks should be inserted in the database during initial database population, so I need to enter them somewhere in db population script. Unfortunately you can’t just put something like this:

db.tests.insert( {
name: 'test',
text: 'this is
my superawesome
multiline content'
} )

Javascript/JSON do not support multiline text like this. Fortunately there are several options that made my life easier. Here they are:

Jun 14, 2013 Oracle Policy Automation Modeler Debugger 10.4.3 is not working with Internet Explorer 10

Oracel Policy Modeler Debugger is not working with Internet Explorer 10. You can still use it to author and compile rules, but debugger with windows just hangs.
There is no official fix for this yet, so your only option is to uninstall IE10 if you can. In windows 7 go to Control Panel->Programs->Programs and features ->View installed updates->Internet Explorer 10->Uninstall.
BTW, OPM is not working with Office 2013 either.

May 17, 2013 FPV Japan / BEVRC Cable pinout

If you don’t hear about it FPV Japan is a small device that records standard definition video from analog sources. This is an indispensable device for FPV RC pilots and the ones who want to digitize old analog video tapes. I fall into both categories, but unfortunately the video cable from my device got burned in an accidental fire that also cause my video blog RTFMS to halt for a really long time. Long sad story …

Anyways, I was repairing the cable recently and decided to pinout it since there seems to be no information in the internet about this very custom cable. So in case if you want to build your own cable here is how it is interconnected:

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