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Practical writing about software, systems, and the small details that make products feel solid.

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Fresh from the notebook

Linux 05 Nov 2026 5 min read

OpenRC Runlevels: Why Enabling a Service Does Not Start It

rc-update add sshd default registers SSH for the default runlevel. It does not start the SSH daemon. Conversely, rc-service sshd start can start the daemon immediately without enabling it for the next boot. That separation is central to OpenRC. A service has a place in the boot configuration and a current runtime state, and those are different things. Confusing them can leave a service running until the next reboot but absent afterward, or registered to start at boot while still stopped today.

Linux OpenRC

Linux 28 Oct 2026 6 min read

Linux 7.3 on Fedora: Why Kernel, Modules, and Initramfs Must Match

Compiling Linux 7.3 produces a kernel image, but that image is only one part of a bootable Fedora installation. On a typical Fedora system, boot also depends on kernel modules, an initramfs assembled for the correct release, and a boot entry pointing to those artifacts. A mismatch can leave a perfectly compiled kernel unable to mount its root filesystem. This matters when using the upstream source from kernel.org rather than Fedora’s kernel RPMs. Fedora’s package installation normally coordinates several boot artifacts. A manual upstream build leaves that coordination to the administrator. The example below assumes an ordinary x86_64 Fedora installation managed with GRUB and grubby, not an rpm-ostree-based desktop.

Linux Fedora

Linux 26 Oct 2026 5 min read

Why Linux Filesystem Tools Report Different Types

A disk partition can contain an ext4 filesystem while a process sees an overlay filesystem at /. Meanwhile, /proc/filesystems may list tmpfs and nfs, neither of which needs a local partition. These are not conflicting answers. They describe different parts of the Linux storage stack. The distinction matters when identifying a volume, investigating an unexpected mount, or checking which filesystem handles an application’s path. A filesystem signature on a device is not the same thing as a mounted filesystem in a process’s namespace.

Linux Filesystems

Artificial Intelligence 04 Oct 2026 4 min read

Temperature Scaling Adjusts Confidence Without Changing Class Order

A classifier can rank classes correctly while assigning probabilities that are too sharp or too flat. Temperature scaling addresses that mismatch with a deliberately narrow transformation: divide every logit for an example by one positive scalar before softmax. For logits z_k and temperature T > 0, the calibrated probability is p_k(T) = exp(z_k / T) / sum_j exp(z_j / T) The scalar is usually fitted on held-out data after the model parameters are fixed. This separation matters because temperature scaling changes reported confidence, not the representation or decision boundary produced during training.

Artificial Intelligence Calibration

Linux 04 Oct 2026 4 min read

SO_REUSEPORT Splits One Listen Address Across Multiple Linux Sockets

A conventional server owns one listening socket for a local address and port. SO_REUSEPORT changes that ownership boundary: multiple eligible sockets can bind the same address, and Linux selects a member of the reuseport group when traffic arrives. The option is useful when several worker threads or processes should receive traffic without sharing one accept or receive queue. It changes kernel-side socket selection, not the transport protocol carried on the network.

Linux Sockets

Artificial Intelligence 04 Oct 2026 4 min read

RoPE Position Indices Must Ignore Padding Tokens

Rotary position embeddings encode token position by rotating query and key coordinates with an angle determined by an integer position index. That index is part of the model input semantics even when it is generated inside a framework wrapper. In a padded decoder batch, using the physical tensor column as the position can therefore change logits for a sequence that has not changed textually. The issue is distinct from attention masking. A mask can stop valid tokens from attending to padding while the valid tokens still receive shifted rotary coordinates. Correct masking and correct position assignment solve separate problems.

Artificial Intelligence Transformers

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