Technical Blog

How Twitter is (probably) crawling the Internet for AI

Me — Tue, 16 Dec 2025 19:40:00 GMT

As a bored sysadmin you might SSH into one of your servers and run htop or tail -f access.log. Last Sunday was one of those tail -f access.log days.

You take a cursory look at your web server logs slowly scrolling past and see a bunch of requests come in. They look a bit odd.

SFTP, root access and sudo

Me — Sun, 13 Jul 2025 18:00:36 GMT

Suppose you log into a server with your own SSH user, have password-less sudo access and want to access files as root over SFTP.

Your attempt would probably look like this:

# sftp user@remote
Connected to remote.
sftp> cd /root
sftp> ls
remote readdir("/root"): Permission denied
sftp> sudo ls
Invalid command.

Not possible, right?

firewalld and common equivalents in iptables

Me — Wed, 12 Mar 2025 09:57:43 GMT

As I increasingly use distributions that rely on firewalld over the old ways of manually configuring iptables this article notes down some common patterns encountered.

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Transcoding a HDR video with tonemapping

Me — Sun, 20 Oct 2024 21:30:00 GMT

Before HDR came into wider use, working with video was easier. You didn't have to care about colorspaces [1], it would display fine everywhere and working with it was painless. Ok, this is oversimplified. But you get the point.

With HDR it's not so simple anymore: To display it a process called tonemapping needs to be applied and you even need a HDR-capable output device in order for a meaningful difference to be visible (compared to SDR, Standard Dynamic Range).

How to trick Windows 10 to install on an USB drive

Me — Mon, 08 Jan 2024 21:50:16 GMT

Suppose you want a Windows installation for your computer, but a bit more portable. You might think to use an external USB but the truth is Microsoft doesn't want you doing this and prevents it in the Windows installer.

Linux package managers cheatsheet

Me — Mon, 13 Nov 2023 21:26:16 GMT

This post isn't for the basic operations like installing stuff, because those are easy to remember or easy to figure out if you're missing them.

Putting a systemd service behind a VPN

Me — Tue, 25 Oct 2022 16:11:06 GMT

It recently occurred that I had the need to route all traffic by a certain application through a VPN. While premade solutions for this exist using Docker (especially in combination with BitTorrent clients), I preferred looking for something that really just isolates what is needed and leaves the rest alone.

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Ad-hoc router using OpenWrt in a VM

Me — Tue, 02 Aug 2022 15:31:54 GMT

During writing of the last post I actually bricked my home router after installing a custom image. At the same time I didn't manage to get TFTP recovery working [1] so I started searching for ways to restore my home network for now to worry about fixing the router later.

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OpenWrt build notes

Me — Thu, 07 Jul 2022 14:22:24 GMT

This post contains Q&A-style notes on compiling software for OpenWrt or compiling OpenWrt itself.

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Headless Raspberry Pi OS virtualization, 64-bit edition

Me — Fri, 29 Apr 2022 14:44:24 GMT

With Raspbian (now named Raspberry Pi OS) having been released as 64-bit, I can finally write a proper sequel to the previous post that dealt with virtualizing ARM/Linux distributions headlessly using QEMU.

You can read the original article here: Virtualizing Raspbian (or any ARM/Linux distro) headless using QEMU. Since the process is the same I will skip detailed explanations here.

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