Used to be my personal blog. Now, it covers programming, low-level development, operating systems, and more.

Programmatically Start Long-Running Command via SSH in Background and Disconnect (and get the PID)

UPDATE: Turns out, I googled the wrong thing/keywords. There is a helpful answer on StackOverflow. It was surprisingly difficult to programmatically start a long-running command via SSH in background and disconnect the SSH session immediately. So, in case you need help, here’s how I did it. The final solution is ridiculously simple. Goal My goal is to programmatically (i.e., from a script) start a command on a remote server. So far so good,...

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Quickly Boot a Minimal Linux Kernel + Initrd in Cloud Hypervisor or QEMU

For various reasons, such as OS development, it is convenient to quickly start up an instance of QEMU or Cloud Hypervisor with a custom kernel and initrd. However, often the major struggle is to get some kernel and some initrd, i.e., the boot items, quickly and easily. Scope Foremost, this blog post is a guideline for direct (Linux) kernel boot, possibly along with a matching initrd. If you can boot an ISO installer...

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Remotely deploying NixOS configuration using SSH Jump Host

nixos-rebuild --target-host <user@host> is a powerful tool to remotely deploy a NixOS configuration. However, there are scenarios where you can’t reach a machine directly but need an SSH jump host. Suppose you want to deploy to the host 192.168.124.42, which is only reachable from the host ssh-gate. Then your nixos-rebuild invocation might look as follows: It’s simple as that. Using -J <jumphost> option (see man page), we instruct SSH to find the right...

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x86 Kernel Development & Relocatable Binaries – What I learned about Toolchains and Relocatable Code

This post is roughly a summary of the obscure knowledge I learned about toolchains and relocatable code in the last couple of years by studying the code of the microkernels NOVA and Hedron, my professional hands-on experience with kernel development, and several learning projects. I present some of the “hard and not obvious” properties of producing kernel binaries, information that only stands “between the lines” in existing projects, and topics I didn’t find Read more…

By Philipp Schuster, ago

Enabling TP-Link Archer TX20U Nano on NixOS and Linux 6.12

Recently, I’ve bought a TP-Link Archer TX20U Nano WiFi USB dongle (vendor website) for my desktop PC. The driver for Windows is provided by the stick itself, as it exposes a storage volume with the Windows driver on it. On Linux, the Windows driver doesn’t work, of course. However, with only minor modifications to the system’s NixOS configuration, we can leverage the already packaged out-of-tree driver for this device and use it for Read more…

By Philipp Schuster, ago
Archer TX20U Nano

Live-Migration of QEMU/KVM VMs with libvirt: Command Cheat Sheet and Tips

Update: The original post is from November 2024. I updated the post in the meantime a couple of times to reflect my latest knowledge. Since recently, I am working with libvirt to perform live-migration VMs with QEMU/KVM VMs (QEMU as VMM and KVM as hypervisor). A few things were not very clear nor well documented. Therefore, I’d like to provide you with this basic cheat sheet and a few tips and tricks. Likely Read more…

By Philipp Schuster, ago

Configure a systemd Service to Perform Side Effects and Corresponding Cleanup

Problem and Motivation For a Linux-based demo setup, I need certain side effects and corresponding cleanup steps every time the system boots or relevant system configuration changes. I’m using NixOS, and systemd is the easiest and most powerful way to manage setup tasks at system startup or on substantial system configuration changes in NixOS. I didn’t need a daemon running in the background (which is the major purpose for systemd services), but specifically Read more…

By Philipp Schuster, ago