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I recently ran into a frustrating problem: I wanted to print a PDF directly from a USB stick, but the printer kept showing “memory device is not working properly.” The drive had previously been flashed with Debian, so I assumed deleting the old files and copying my PDF would be enough. This was, of course, not the solution. In this short article, I cover what I did to fix the problem.
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Recently my Ubuntu installation ended up in a broken state after a reboot:
external displays stopped working, nvidia-smi failed inside the desktop
environment (DE), and the system would hang while stopping gdm during
shutdown. Interestingly, the NVIDIA driver still worked in recovery mode, which
suggested the kernel modules themselves were not completely broken. I decided
to reset both the NVIDIA stack and the DE entirely since I
have had issues in the past with GPU weirdness.
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Often I have to perform substitution of variables or code blocks with something
new as part of refactoring efforts. Since I am using nvim, I wanted a way to
do this without having to close nvim, but also taking advantage of highly
optimized regex search utilities like ripgrep. In this short how-to, I
provide the commands one can use to do this without ever having to close nvim.
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If you choose to host a self-managed (i.e. private) GitLab instance on on-premises infrastructure, you do not get access to GitLab’s shared (public) runners for CI/CD. Unlike GitLab.com or GitLab Dedicated, a private GitLab instance puts you fully in control, but that control comes with responsibility: you have to bring your own runners. In this article, I document my experience setting up a GitLab runner on a Raspberry Pi 3B+, why I chose this route, and how I did it. Spoiler: while the setup itself is fairly straightforward, there are some Raspberry Pi–specific hardware quirks that are worth handling correctly if you care about long-term stability and recoverability.
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I am constantly using ssh to remotely login to different compute clusters
(e.g., DKRZ’s Levante, ECMWF’s Atos, local clusters at work, etc.). I find it
much more convenient to use a terminal-based text editor like
neovim coupled with the standard terminal
multiplexer tmux in order to switch easily
between several programs in one terminal. However, I quickly encountered an
issue where my neovim color scheme was not displayed when using it within tmux.
Fortunately, there’s an easy fix to this issue that I cover in this article. I
first show the problem and the expected behavior, diagnose the error, and then
correct it accordingly. I document the solution here and tie to use with
legacy systems.
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I often download and read scientific journal articles on my Kobo eReader.
Unfortunately, the metadata in the PDFs for such journal articles may lack title
information. This means that the searchable title that appears for the article
once loaded onto the eReader is something very ugly like an uninterpretable
string of digits. An easy way to fix this is using the open-source tool pdftk.
In this short article, I show how to use pdftk for this purpose.
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In this article, some extra mathematical details related to the solution of the steady-state reaction-diffusion equation using PETSc are discussed. First, the simple nonlinear governing equation of interest is shown. Then, Newton’s method is presented at the partial differential equation (PDE) level for generality rather than being presented at the algebraic level. Subsequently, the spatial discretization via the finite difference method is shown for completeness. Finally, a commented PETSc implementation of the discretized reaction-diffusion equation is shown to concretely illustrate how the mathematical notation maps to code.