Network

I noticed that the Web UI of the Pi-hole I run at home (http://127.0.0.1:8053/admin) had become completely unreachable. All I got back was Connection reset by peer, and neither the browser nor curl could see anything. DNS resolution (port 53) was still working fine, so there was no real damage. As far as docker ps went the container was shown as healthy, so I had not been worried, but when I looked into it I found that the problem itself went back six days, to 2026-08-01. [Read More]

The IP address ledger I had been keeping in GoogleSpreadSheet was no longer keeping up as the number of devices grew. The IP addresses actually in use and what the sheet said drifted apart more and more, and I was reaching the limit of taking stock by hand, so I decided to start phpIPAM with Docker and move IP management there. Starting it with Docker I settled on the following docker-compose.yml. [Read More]

Introduction: the late-night “what was this port again?” problem When you run servers, you repeatedly end up in the situation where you see an alert in the middle of the night, SSH into the machine, and think “what is listening on this port again?” Until now I combined netstat / ss / lsof / nmap / systemctl / docker ps and worked out the identity and the origin of the process by hand. Recently I started using a CLI tool called witr (Why is this running), and because it explains in a single command even why a process exists, my investigation flow has changed considerably. [Read More]

I had already finished the move from Netlify to Cloudflare on my other blog, and since the summer holidays gave me some time, I did the migration on this site too. It was almost the same work as the migration on the other blog, so I was able to move over fairly easily. Github To link it with Cloudflare, set the repository in question to allow the integration. [Read More]

It is what you would call a SaaS style operations monitoring service I now have an environment where I can use Datadog, so I am thinking of migrating from my Zabbix server. Since it is just the Zabbix server being replaced by Datadog’s service and zabbix-agent being replaced by datadog-agent, anyone who uses Zabbix should be able to grasp how it works. Once you register an account on the Datagog side so that you can use it, install Datadog-agent on the machines of each platform and start it, you will be able to view beautiful visualized graphs in no time at all. As for installing datadog-agent, various platforms are provided, but most people probably run it on CentOS or Debian Linux. Installation is easy too, with what is pretty much a one-liner command [Read More]

On my home server I run several nginx-proxy Docker containers, and I also make them accessible from outside on my own domain. Of course, on the fiber router facing the WAN I have ports 80 and 443 open, and connectivity from outside is confirmed. In this kind of setup, a symptom where access from outside was not possible started happening at irregular intervals Symptoms When the problem shows up from outside, access becomes impossible with a 403 Fobidden like the one below [Read More]

Environment where the problem happens Model: TS-269 Pro Old firmware: 4.3.4.1029 New firmware: 4.3.4.2351 File sharing from Windows10 and sharing over Mac SMB could no longer connect as guest. Guest login worked on the old firmware, but after the new firmware guest login stopped working Checking the settings In Control Panel → Privilege settings, under “Edit Shared Folder Permission”, I confirmed that the files (folders) that should allow guest login have read/write checked for everyone In Control Panel → Network & File Services, under “Microsoft Networking”, I confirmed that “Enable file service for Microsoft networking” is checked I unchecked “Enable file service for Microsoft networking” and pressed the Apply button, then checked it again and pressed the Apply button (restarting the file sharing service) Even after all of these checks, guest login does not work [Read More]