Original, source-backed articles about running small systems, static sites, HTTP, DNS, TLS, and operations.
Posts are original articles written for this site. Each one is script-free, source-backed, and tied to the same operational reality the rest of the site records: how a small, static, publicly served system is built, secured, and kept honest.
InnoDB deadlocks roll back the whole victim transaction
An InnoDB deadlock occurs when transactions form a cycle of incompatible lock requests. With deadlock detection enabled, InnoDB chooses a victim and rolls back that entire transaction so another participant can proceed. The application receives error 1213 with SQLSTATE 40001. Retrying only the statement that reported the error omits earlier work that was rolled back with it.
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dnsmasq separates forwarded cache entries from configured local names
dnsmasq can forward DNS questions upstream, retain supported answers in a bounded cache, and serve names configured locally. These are different sources of data. A repeated answer may be a cache hit or a local configuration result. Establishing which source supplied it is essential when a hostname disagrees with the authority or continues resolving after a cache flush.
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LVM snapshots capture a block device in time
An LVM snapshot is neither a copy nor a reflink: it is a fixed-size copy-on-write exception store attached to an origin logical volume. lvcreate -s -L 5G -n snap vg/data allocates 5 GiB from the volume group, and the device-mapper snapshot target records the original contents of each origin chunk the first time it is written. Creation is instant whatever the origin’s size, because nothing is copied.
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Consul keeps a live map of healthy services
A service registry is only as useful as its honesty. Consul keeps a catalog of registered instances and attaches health checks to them, so a caller asking where a healthy instance of a service lives gets an answer that changes as reality changes. Registration is trivial; the check is the whole product, because a registry that lists dead instances is worse than a static list — it actively routes traffic into a hole.
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The scheduler accounts for requests, not momentary utilization
Kubernetes scheduling answers whether a Pod can fit a node under the applicable resource requests and placement constraints. It does not simply look at a current CPU utilization chart and place work wherever the line is low. Requests provide accounting inputs for future demand; actual usage is a separate observation. Diagnose both before deciding that an idle-looking cluster has capacity for a particular Pod.
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Baggage carries context across an explicit boundary
OpenTelemetry baggage is a context-associated collection of string key-value pairs. It lets information known near a request’s entry point travel to downstream operations: a deployment region or a rollout cohort, for example. Unlike a span attribute, baggage is intended for propagation. Unlike trace context, it describes application-selected information rather than the identifiers and flags connecting spans. These mechanisms can travel together without being the same data structure.
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The TCP backlog holds connections that are still syncing
A listening TCP socket has two queues, not one, and the sysctl this article is named after governs the queue that almost never drops anything. The backlog passed to listen(2) is the accept queue, holding connections that finished the handshake and await the application; the SYN queue holds half-open requests. Confusing them produces the wrong fix.
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ZFS snapshots give the filesystem a rewind button
A ZFS snapshot is a name attached to a dataset’s block tree at one transaction group. Nothing is copied, nothing is quiesced, and the cost is a few metadata blocks: zfs snapshot tank/data@before-upgrade returns before the shell prompt redraws. Because ZFS never overwrites a live block in place, the old tree stays valid on disk until the last reference to it goes away, and the snapshot is that reference.
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