Containerization

Software that implements one platform's API on top of another's, so unmodified programs run somewhere they were never built for.

The binary-level contract that lets separately compiled code work together, covering registers, data layout, and symbol names, and why breaking it forces everything to be rebuilt.

An agent run that continues without a person watching, started by a schedule, an event, or a handoff, and reports its results when done.

Rebasing a process's idea of the filesystem root, the oldest and shallowest form of Unix process isolation.

Automatically releasing every change that passes validation.

The Linux kernel feature that caps and accounts for a process group's CPU, memory, and I/O — the resource-limiting half of a container.

A single file holding the complete contents and structure of a disk, used to install operating systems, run virtual machines, preserve old media, and copy drives exactly for forensic investigation.

A tracked repository of personal configuration, making a machine setup reproducible.

Loading a program's libraries at run time from shared files instead of copying them into the executable, which saves space and eases patching at the cost of fragile dependencies.

A named value in a process's environment, inherited by its children — the standard configuration channel.

How programs learn that files changed, by polling or by kernel notification interfaces such as inotify and FSEvents, and the many ways those notifications get lost, delayed, or exhausted.

The layer that lets multiple guest operating systems share one machine's hardware, each believing it owns the machine.

Replacing servers wholesale on every change instead of patching them in place.

A system that runs containers across a cluster of machines by continually reconciling what is running with a declared desired state, powerful and notoriously complex.

A complete operating system assembled around the Linux kernel, combining it with system tools, a package manager, and a set of opinions about release cadence, defaults, and freedom, with hundreds in active use.

The kernel feature that gives a process its own private view of a global resource — the foundation containers are built from.

The smallest self-contained program or set of steps that still shows a bug, and why making one is often the moment the bug gets understood.

Rewriting the addresses in packets as they cross a router so that many devices can share one public IPv4 address, a stopgap that became permanent and broke the internet's end-to-end design.

The numeric endpoint a network service listens on, and a scarce shared resource on a developer machine.

A server that sits in front of other servers and receives clients' requests on their behalf, handling encryption, routing, caching, and protection in one place.

The all-powerful root account on Unix systems, how sudo hands out its power temporarily, and why both attackers and good security design revolve around who gets it.

A file that points at another path, resolved transparently by most operations.

The dominant Linux init system, replacing sequential startup scripts with declarative, parallel, dependency-aware units.

Civil time is a political layer over solar time, and its rules change often enough to be data.

Renting space on someone else's servers to put a website online, a business that moved from free personal pages and crowded shared machines to virtual servers, rented cloud infrastructure and services that host static files at the edge of the network.

A convention placing configuration, data, cache, and state in defined directories rather than the home directory.