Resize the RAID1 root partition without rebooting

Resizing the root partition on a server 12 miles away seemed a bit risky. The root partition is on a software RAID1 mirror, no LVM. Twelve years ago I left only 2 GB for the root partition. I wanted to upgrade to Ubuntu 20.04.5 and the small size quickly became a problem. I managed to upgrade to Ubuntu 18.04.6 LTS, but ran out of space while upgrading to 20.04.5 LTS. Even after uninstalling previous versions, there was not enough space left. I had to make the root partition bigger. There was a relatively large 8 GB swap partition right after the root partition. The RAM is only 2 GB, so I was able to reduce the size of the swap. The plan was to delete the swap and extend the root partition, then create a smaller swapfile. I’ll show you how I did it. The server did not have to be restarted even once during the partition conversion. Finally, I have 5 GB free space after upgrading to Ubuntu 20.04.5 LTS.

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Sort numbers before adding up!

A few years ago my teammate came up with this statement. At first we misunderstood each other. I thought of integer numbers while he meant floating point. I know how the processor represent floats and I’m aware of how/why floating point numbers are normalized or rounded. But to be honest, I never thought the order of adding numbers is relevant. Ok, let see is it important or not. Before starting I have to say, this is all about floating point numbers, integers are not affected.

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How to disable Windows auto sleep in AC mode with code

It can be annoying if you use your computer 24/7 and when you don’t interact with the desktop, your machine will go into sleep after a while. If you’re using the PC remotely, you cannot bring it back from sleep. You can also turn off sleep mode manually in Power & sleep under System preferences by changing the “When plugged in, PC goes to sleep after” setting to Never.

Or even better, you can modify it with the PowerCfg utility by invoking the following command:

This should be a simple set-and-forget option, but surprisingly, this setting can sometimes revert to its original value. I didn’t spend time trying to figure out why the value can change, instead I got my supervisor application watch and reset the value. Here’s how I figured out (debug) how to do it with API calls, and of course I’ll show you the working source code (C++, C#, Delphi).

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R.I.P. Sir Clive Sinclair

Another day of sadness to mark on the calendar, as someone has written on the World of Spectrum forum. He passed away on 2021.09.16 at the age of 81. I owe my interest and love in computers to him. Rest in peace Sir!

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Localhost tcp traffic stalled

After installing a 4G/LTE USB stick on a Windows 7 desktop the TCP communication on localhost has effectively stalled. Interestingly, the remote traffic was not affected. Local services can be reached by remote clients and remote services can be accessed from the desktop, only the localhost (127.0.0.1) is affected. Still ping (ICMP) works on localhost as before. Capturing the traffic reveals that all localhost services communicate through TCP become utterly slow. The TCP session starts by a zero window packet in both direction right after the SYN-SYN/ACK handshake. After that, only 1 byte payload arrives in 20-60 seconds interval. Most clients give up after 30 seconds and return error. The problem persist after removing every installed software and turning off the Windows Defender service. It doesn’t matter which port the service is listening on.

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Bomberman / Dynablaster DX11

This is a quick update to the version I published many years ago. A lot has changed under the hood and yet much remains the same.

Click on the picture to download the game

Basically, the DirectX 9 API was replaced by Direct 3D 11 and a few minor bugs was fixed. We played a lot with this version on Windows 10 so I believe it’s free of bugs.

Added benefit of the new API is that you don’t have to download a DirectX runtime from Microsoft anymore. It should be working immediately without any additional download, at least on Windows 10.

The menu is as plain as in the original Amiga (or PC) version. This is intentional, it’s like playing in an emulator. However, I hope I will release a more user friendly advanced version soon.

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256b demo – Function 2019

Some people think 256 bytes doesn’t enough for anything. To be prove they’re wrong just watch “Puls by Rrrola” or “Stainless Steel by Digimind” on Youtube. You can find more jaw-dropping products if you search for “256b demo”.

I created a simple waving-colors effect which was called color-plasma in the old demo days. As simple as it is but looks mesmerizing. I called it Hypnotize. If you watch it long enough you will know why.

Click to download from ftp.scene.org

How much is 256 bytes.

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Configure WSUS/GPO programmatically

We have a few hundred Windows PCs across the country. It is essential to keep the OS up to date, just think of the new BlueKeep vulnerability. These PCs are running 7/24 unattended, so we need to automate almost everything, including the Windows Update configuration. These PCs are completely separate from the intranet and do not connect to the Windows Domain, but they have to use the company’s WSUS servers. Each computer had the WSUS server pre-configured using the Local Group Policy (gpedit.msc), but after a few years we had to change the server address. Each PC is supervised by our custom management software. It was obvious that the WSUS server setting should be deployed through the same management system, as well as other settings. Read the rest of this entry »

Rise and fall of WAP

In the perspective of an engineer…

I started working as a Service Quality engineer at a telecom company in 2001. After many small projects a manager asked me whether I can create a software to grab the content of our entire mobile site to verify everything, literally (broken links, grammar, changes, pictures etc). Mobile sites were using WAP technology back then and there was no deep knowledge on how to communicate via the WAP protocol. I got a small byte array (less than 50 bytes long) from a WAP Gateway operator which meant to be the WAP request. The software used it to generate the WAP request by appending the URL to it. That was a simple WAP Class 0 (connectionless) transaction. I sent one UDP packet with the request then the WAP Gateway sent me the response. That was it.

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Software controlled infrared device

After a long silence I pushed myself to create a new article. I have many half written materials I can choose from. This time I finished my IR device story.

In 2008 my then boss came up with an idea: End-to-End testing/monitoring of the TV services by using real set-top-boxes (STB). One of the interesting part of this project was the development of the software controlled infrared remote device. E2E mean we had to control an STB just like clients do, so a computer controlled IR had to be developed. We intended to simulate the original remote, so I had to watch-and-learn the signal it sent.

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