Every yarn install is a network request away from failure. The npm registry can go down, a corporate proxy can block a scoped package, or a build server can be air-gapped entirely. Yarn’s offline caching and mirroring features exist to eliminate that dependency: once packages are downloaded, they are stored locally and can be reused…
GitHub Pages turns a repository into a static website. It is not a general-purpose web host. It serves HTML, CSS, JavaScript, and assets directly from a branch or a GitHub Actions artifact, with no server-side execution, no database, and no dynamic request handling. For documentation, project landing pages, and personal blogs, it is free, integrated…
A tag is a Git concept: a fixed pointer to a specific commit that never moves. A release is a GitHub concept layered on top of a tag: a page with release notes and downloadable binary artifacts. Confusing the two is common. You can tag a commit without creating a release, but you cannot create…
GitHub Projects (v2) is not a board. It is a database with multiple views. This distinction is the single most important concept to internalize before touching the interface. The classic Projects product—columns of cards, one board per repository—is deprecated and being retired. The modern Projects product stores items as rows in a table, and the…
A repository is only as safe as the gates that guard its main branch. Branch protection rules are those gates: they define who can push, what must pass before a merge, and whether history can be rewritten. CODEOWNERS is the routing table that ensures the right people review the right files. Used together, they turn…
A pull request is the proposal. Merging is the execution. When a pull request is approved and its checks pass, GitHub offers three distinct buttons: “Merge commit”, “Squash and merge”, and “Rebase and merge”. These are not cosmetic variations of the same action. Each produces a fundamentally different shape of Git history, and the choice…
The nmcli command is the primary interface for NetworkManager. It translates human-readable commands into D-Bus messages that the daemon processes. The LFCS exam tests the command syntax for creating, modifying, activating, and deleting connections, with particular attention to the distinction between modifying a profile (which saves the configuration) and activating it (which applies the configuration…
NetworkManager is a daemon that manages network interfaces and connections on modern Linux systems. It is not a configuration file format or a wrapper around ip—it is a privileged service that runs in the background, detecting hardware, activating profiles, and applying configuration through the kernel. The LFCS exam tests the conceptual model: the separation between…
The routing table is the kernel’s map of where to send packets. Every packet destined for an address that is not on a directly connected subnet must be matched against a route entry to determine the next hop—the gateway that will forward the packet toward its destination. Without a default route, a host can only…
The previous chapter covered ip addr, which manages Layer 3 protocol addresses. But an address is meaningless if the underlying link is administratively disabled. The ip link command operates one layer below: it manages the network device itself—bringing it up or down, changing its MTU, altering its MAC address, and creating virtual devices like bridges,…