Linux on ma.ttias.be

Linux debugging tools I use daily

mattias@ma.ttias.be (Mattias Geniar) — Fri, 12 Jun 2026 00:00:00 +0000

Every server I run, including the fleet behind Oh Dear ’s uptime checks, has the same set of debugging tools installed before anything goes wrong. Not because the application needs them, but because the one time you reach for strace is at 2am, the box is misbehaving, and apt install is the last thing you want to be doing while you work out what broke.

A fresh server for this blog

mattias@ma.ttias.be (Mattias Geniar) — Sun, 28 Dec 2025 00:00:00 +0000

It’s been 1,067 days since I last posted something on this blog. And instead of writing the blog post I wanted to write, I did everything else.

cargo: no such subcommand: +nightly

mattias@ma.ttias.be (Mattias Geniar) — Mon, 23 Nov 2020 00:00:00 +0000

I was trying to run the following command:

$ cargo +nightly install [package]
error: no such subcommand: `+nightly`

But … that didn’t work. This was my fix:

OpenSSL pkg-config not found

mattias@ma.ttias.be (Mattias Geniar) — Mon, 23 Nov 2020 00:00:00 +0000

I found this error message when compiling some software from source:

It looks like you're compiling on Linux and also targeting Linux. Currently this
requires the `pkg-config` utility to find OpenSSL but unfortunately `pkg-config`
could not be found. If you have OpenSSL installed you can likely fix this by
installing `pkg-config`.

Luckily, it’s an easy fix!

wabt-sys compile: error: CMAKE_PROJECT_VERSION was not declared in this scope on Ubuntu 18.04 LTS

mattias@ma.ttias.be (Mattias Geniar) — Mon, 23 Nov 2020 00:00:00 +0000

When trying to compile WebAssembly (wabt-rs) for a dependent package, it failed on Ubuntu 18.04 LTS due to this error message.

Recap: measuring linux performance - how to avoid typical mistakes

mattias@ma.ttias.be (Mattias Geniar) — Thu, 09 Jul 2020 06:50:00 +0100

In the last two weeks, Peter Zaitsev published a 4-part series on measuring Linux performance on this blog.

How to measure Linux Performance Avoiding Most Typical Mistakes: Network

mattias@ma.ttias.be (Mattias Geniar) — Wed, 08 Jul 2020 06:50:00 +0100

In this series, we are talking about Linux performance measurement, how to measure it right. Linux performance is a very broad topic, so we’ll focus on the four primary resources which are typically going to drive your system performance – obviously CPU, memory, disk storage, and network.

How to measure Linux Performance Avoiding Most Typical Mistakes: Memory

mattias@ma.ttias.be (Mattias Geniar) — Mon, 06 Jul 2020 06:50:00 +0100

How to measure Linux Performance Avoiding Most Typical Mistakes: Disk Storage

mattias@ma.ttias.be (Mattias Geniar) — Thu, 02 Jul 2020 06:50:00 +0100

Adding SWAP to Linux

mattias@ma.ttias.be (Mattias Geniar) — Tue, 30 Jun 2020 00:00:00 +0000

Here are the steps needed to add a new SWAP partition to your Linux machine. This’ll allocate 2GB of space on your disk, and allow it to be used as RAM if your server is running low.

How to measure Linux Performance Avoiding Most Typical Mistakes: CPU

mattias@ma.ttias.be (Mattias Geniar) — Mon, 29 Jun 2020 00:00:00 +0000

In this series, we are going to talk about Linux performance measurement, how to measure it right. Linux performance is a very broad topic, so we’ll focus on the four primary resources which are typically going to drive your system performance – obviously CPU, memory, disk storage, and network.

Reading .EML mail files using Mutt on Mac OSX

mattias@ma.ttias.be (Mattias Geniar) — Fri, 26 Jun 2020 00:00:00 +0000

As part of the cron.weekly newsletter , I want to test the plain-text version of the mail as much as possible.

Making life easier with cron

mattias@ma.ttias.be (Mattias Geniar) — Thu, 04 Jun 2020 00:00:00 +0000

This post shares some ideas about working with cronjobs, to help make common tasks more easy for both junior and senior sysadmins.

MySQL: ERROR 1153 (08S01): Got a packet bigger than 'max_allowed_packet' bytes

mattias@ma.ttias.be (Mattias Geniar) — Fri, 15 May 2020 00:00:00 +0000

I ran into this error when doing a very large MySQL import from a dumpfile.

Create a date in the future for use in Bash scripts on BSD/Mac OSX

mattias@ma.ttias.be (Mattias Geniar) — Thu, 14 May 2020 00:00:00 +0000

Annoyingly, the date command differs vastly between Linux & BSD systems. Mac, being based on BSD, inherits the BSD version of that date command.

Bash script to send a push notification when string is found in logs

mattias@ma.ttias.be (Mattias Geniar) — Sun, 03 May 2020 00:00:00 +0000

I had a use case where I wanted to be notified whenever a particular string occured in a log file. This seemed a bit overkill to make a custom implementation in a monitoring solution, so I wrote a simple Bash script to send me a push notification whenever it occurs.

How I write and curate the cron.weekly newsletter

mattias@ma.ttias.be (Mattias Geniar) — Wed, 29 Apr 2020 00:00:00 +0000

Every Sunday, I send out a newsletter called cron.weekly to over 10.000 subscribers. In this post, I’ll do a deep-dive into how those mails get delivered to subscribers.

Deploying a highly-available K3s with K3sup

mattias@ma.ttias.be (Mattias Geniar) — Mon, 27 Apr 2020 00:00:00 +0000

Introduction#

Some of members of the cloud-native computing world have recently been trying to find a way to address the areas where Kubernetes falls short when trying to run on resource constrained environments.

Clean up Linux Server Using These Simple Tips

mattias@ma.ttias.be (Mattias Geniar) — Sun, 26 Apr 2020 00:00:00 +0000

Deploying a Linux server is really easy these days thanks to the abundance of cloud server providers like Linode, Digital Ocean etc. This enables not-so-expert people, like me, to deploy and manage their own Linux servers.

Different ways of writing crontab syntax

mattias@ma.ttias.be (Mattias Geniar) — Sun, 26 Apr 2020 00:00:00 +0000

Here’s what I’ve been doing for most of my life, when it comes to writing crontab entries:

Convert a PuTTY private key to openssh

mattias@ma.ttias.be (Mattias Geniar) — Sat, 22 Feb 2020 00:00:00 +0000

I recently got a PuTTY private key sent to me that I wanted to use to log into a remote server. But, I run OpenSSH, not PuTTY.

Accepting new sponsorships for the cron.weekly newsletter

mattias@ma.ttias.be (Mattias Geniar) — Fri, 31 Jan 2020 00:00:00 +0000

In case you’ve missed it: the cron.weekly newsletter is back!

I’m about 6 issues in to the new season and I feel I’ve gotten a good flow going. The boring stuff is automated, the toolchain is solid and I’m enjoying writing once again. 💪

Dumping specific tables in MySQL using mysqldump

mattias@ma.ttias.be (Mattias Geniar) — Fri, 17 Jan 2020 00:00:00 +0000

Here’s a small little trick when using mysqldump: you don’t have to dump an entire database, you can dump individual tables too.

Auto-restart a crashed service in systemd

mattias@ma.ttias.be (Mattias Geniar) — Mon, 13 Jan 2020 00:00:00 +0000

Systemd allows you to configure a service so that it automatically restarts in case it’s crashed.

What exactly is being sent to Ubuntu in the MOTD?

mattias@ma.ttias.be (Mattias Geniar) — Sat, 28 Dec 2019 00:00:00 +0000

There’s a tweet going around in the last few days that highlights that Ubuntu’s default MOTD (Message of the Day) fetches information from an Ubuntu server. In the process, it sends along quite a bit of personal & identifiable information of your desktop or server back to Ubuntu.