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LVM Thinpool Restore

Configuring Linux **nix *

Hi everyone, today I will tell how I restored a defunct LVM thinpool. Unfortunately I could not find any howtos or manuals on the internet, so maybe this one will help someone in a similar situation.

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Total votes 2: ↑2 and ↓0 +2
Views 462
Comments 0

Controlling Brushless Motors using a Linux computer or a PLC

*nix *SCADA *Computer hardware DIY Electronics for beginners

In this video, we will look at how to connect brushless motor controllers to a Linux computer. Specifically, we will use a computer running Debian. The same steps would work for Ubuntu Linux and other Linux distributions derived from Debian.

I've got a small sensorless brushless motor, and a bigger brushless motor with a built-in absolute encoder. Lets look at how to control those from my Debian Linux computer. Servosila brushless motor controllers come in several form factors with either a circular or a rectangular shape. The controllers come with a set of connectors for motors and encoders as well as for USB or CANbus networks.

The controllers can be powered by a power supply unit or by a battery. To spice up my setup, I am going to use a battery to power the controllers and thus their motors. The controllers need 7 to 60 volts DC of voltage input. If I connect the battery, the controllers get powered up. The small LED lights tells us that the controllers are happy with the power supply.

We need to connect the brushless motor controllers to the Linux computer. There are two ways to do that - via CANbus or via USB. Lets look at the USB option first. A regular USB cable is used. Only one of the controllers needs to be connected to a computer or a PLC.

Next, we need to build an internal CANbus network between the controllers. We are going to use a CANbus cross-cable to interconnect the controllers. Each controller comes with two identical CANbus ports that help chain multiple controllers together in a network. If one of the interconnected brushless motor controllers is connected to a computer via USB, then that particular controller becomes a USB-to-CANbus gateway for the rest of the network. Up to 16 controllers can be connected this way via a single USB cable to the same control computer or a PLC. The limit is due to finite throughput of the USB interface.

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Total votes 4: ↑3 and ↓1 +2
Views 964
Comments 0

The Implementation of a Custom Domain Name Server by Using С Sockets

*nix *DNS *C *SQLite *

We describe the implementation of a custom Domain Name System (DNS) by using C socket programming for network communication, together with SQLite3 database for the storage of Internet Protocol (IP) for Uniform Resource Locator (URL). Then we provide a performance analysis of our implementation. Our code is available publicly [1].

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Total votes 5: ↑4 and ↓1 +3
Views 793
Comments 0

Using kconfig for own projects

Configuring Linux **nix *Development for Linux *


Every Linux professional write scripts. Someеimes light, linear. Sometimes complex script with functions and libs(yes, you can write your bash-library for use in other scripts).

But some of the scripts need a configuration file to work. For instance, I wrote a script that builds the ubuntu image for pxe, and I need to change the build process without build-script changes. The best way to resolve this task is to add configuration files.

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Total votes 2: ↑2 and ↓0 +2
Views 2.9K
Comments 1

Porting packages to buildroot using the Zabbix example

Configuring Linux *Open source **nix *Development for Linux *Software

The basics of porting

Originally, Buildroot offers a limited number of packages. It makes sense — there is everything you need, but any other packages can be added.

To add a package, create 2 description files, an optional checksum file, and add a link to the package in the general package list. There are hooks at different stages of the build. At the same time, Buildroot can recognize the needed type of packages:

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Total votes 2: ↑2 and ↓0 +2
Views 2.2K
Comments 0

Safe-enough linux server, a quick security tuning

Information Security *System administration **nix *Cloud computing *Server Administration *
The case: You fire up a professionally prepared Linux image at a cloud platform provider (Amazon, DO, Google, Azure, etc.) and it will run a kind of production level service moderately exposed to hacking attacks (non-targeted, non-advanced threats).

What would be the standard quick security related tuning to configure before you install the meat?

release: 2005, Ubuntu + CentOS (supposed to work with Amazon Linux, Fedora, Debian, RHEL as well)


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Total votes 7: ↑6 and ↓1 +5
Views 1.8K
Comments 0

How I fix cups-printing in Buildroot

Configuring Linux *Open source **nix *Development for Linux *



Like I said earlier in previos articles, Buildroot is a great system for embedded Linux development. But sometimes strange things can happen.

Once upon a workday, I got the following task: add printing system in firmware (Kraftway terminal Linux next generation). Ok, so I had to add cups + cups filter and to build firmware. I set a postscript-printer and got an error "Filter failed". Trivial tasks turned into serious work.

In this article, I wrote my own way of solving this problem. It may be useful for other developers and IT-specialist and, also, for a deeper understanding of the Buildroot.

If you are a Buildroot beginner, I recommend reading my previous articles.

Update 1 may 2020

Revisioned versions of this patches applied to master.

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Total votes 2: ↑1 and ↓1 0
Views 1.1K
Comments 0

buildroot — my own experience with multi-platform distro creation

Configuring Linux *Open source **nix *Development for Linux *


In my previous article (Monitor linux) I wrote, what is this distro and how it works. Now i will write how to do it. It's may be interesting for everyone, who want to study buildroot.

Target goals

The result we get from article is the following:

  • Firmware (non-volatile image with restorable config)
  • Easy management via web-interface
  • Cross-platform (qemu x86_64, arm-based SBC like rasberry 4, beagle bone black and asus tinker board)
  • Support without extra effort
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Total votes 8: ↑6 and ↓2 +4
Views 3.1K
Comments 2

Monitor linux — cross platform firmware with zabbix server

Open source *IT Infrastructure **nix *Development for Linux *Development for Raspberry Pi *


This is small cross-platform linux-distro with zabbix server. It's a simple way to deploy powerful monitoring system on ARM platfornms and x86_64.

Worked as firmware (non-changeable systemd image with config files), have web-interface for system management like network settings, password and other.

Who is interested

  • System admins/engineers who need to fast deploy of zabbix server.
  • Everyone, who want to deploy zabbix on ARM.
  • Enthusiasts
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Total votes 3: ↑3 and ↓0 +3
Views 1.4K
Comments 0

Fast and effective work in command line

*nix *Shells *

There are a lot of command line tips and trics in the internet. Most of them discribe the trivials like "learn the hotkeys" or "sudo !! will run previous command with sudo". Instead of that, I will tell you what to do when you have already learned the hotkeys and know about sudo !!.

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Rating 0
Views 1.9K
Comments 2

Down the Rabbit Hole: A Story of One varnishreload Error — part 1

*nix *Shells *Debugging *DevOps *

After hitting the keyboard buttons for the past 20 minutes, as if he was typing for his life, ghostinushanka turns to me with a half-mad look in his eyes and a sly smile, “Dude, I think I got it.

Look at this” — as he points to one of the characters on screen — “I bet my red hat that if we add what I’ve just sent you here” — as he points to another place in the code — “there will be no error anymore.”
Slightly puzzled and tired I modify the sed expression we’ve been figuring out for some time now, save the file and run systemctl varnish reload. Error message gone…

“Those emails I’ve exchanged with the candidate,” my colleague continues, as his smile changes to a wide and genuine grin, “It suddenly struck me that this is the very same exact problem!”

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Total votes 4: ↑3 and ↓1 +2
Views 675
Comments 0

Apply Nix-Shell environment in Visual Studio Code

*nix *Visual Studio *Development for MacOS *Development for Linux *

A lot of developers faced a problem with packages hell on their workstation. After a couple of months with experiments, including different languages and toolchains, I installed Elixir, Haskell-stack, Node.js/NVM, and other various stuff. Most exciting things happen when you need different versions of the same package for different projects. Humanity already invented a different solution for creating an isolated environment and switch them when needed. We are using NVM to manage Node.js versions, Python Virtual Env for selecting Python stuff versions or Docker for creating OS inside an OS. But none of the solutions satisfy all my requirements for the isolated development environment.
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Total votes 7: ↑7 and ↓0 +7
Views 3.3K
Comments 0

12.3 million of concurrent WebSockets

High performance *C++ **nix *Lua *
Recovery mode

One thing about WebSockets is that you need a lot of resources on the client's side to generate high enough load for the server to actually eat up all the CPU resources.

There are several challenges you have to overcome because the WebSockets protocol is more CPU demanding on the client's side than on the server's side. At the same time you need a lot of RAM to store information about open connections if you have millions of them.

I've been lucky enough to get a couple of new servers for a limited period of time at my disposal for the hardware "burnout" tests. So I decided to use my Lua Application Server — LAppS to do both jobs: test the hardware and perform the LAppS high load tests.

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Total votes 6: ↑3 and ↓3 0
Views 8.3K
Comments 0

Using Linux Kernel Sequence Files

Open source **nix *C *
A characteristic feature of modern programming is the use of the global network as a source of reference information, in particular, a source of patterns for solving unknown or little-known problems for a specific programmer. Such an approach saves a lot of time and often gives quite qualitative results. However, the solutions laid out in the network although usually correct, do not always take into account all the subtleties of solving a problem, which leads to the appearance in the source code of sections that usually work correctly, but under not quite standard circumstances become sources of unpleasant surprises.

Consider the topic of using sequence files in the Linux kernel, such files are considered to be the most convenient mechanism for printing from kernel mode. But in practice, using them correctly is much more difficult than you would think.

A lot of materials on this topic are available online. The best is the source code of the kernel itself which has quite detailed comments. The problem with this source of information is its volume. If you do not know exactly what to look for, it is better if you only have limited time, not to try at all. For me, when I became interested in the topic, Google provided several seemingly excellent sources of information relating to my search: the famous book The Linux Kernel Module Programming Guide and a series of articles by Rob Day. These sources are not new, but very solid.
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Total votes 8: ↑7 and ↓1 +6
Views 3.3K
Comments 1

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