The previous chapter covered how the router matches a URL against the route objects. This chapter covers the case where no route matches. The fallback route is the mechanism for handling unknown URLs. Without it, an unmatched URL renders nothing—an empty page with no navigation, no error message, and no way to recover except editing…
The previous chapter created the router and attached it to the React tree with RouterProvider. This chapter covers the route objects that the router uses to decide which component renders for a given URL. A route object is a configuration record: it has a path, a component (or element), and optionally children, a loader, an…
The previous chapter installed the react-router package. This chapter configures the root provider that connects the router to the React tree. In Data mode, the entry point is createBrowserRouter, which accepts an array of route objects and returns a router instance. That instance is passed to <RouterProvider>, which renders the matching route components and manages…
The React Router ecosystem underwent a significant structural change with the release of v7 and v8. The most consequential detail for installation is that the react-router-dom package was removed entirely in v8. Any tutorial or documentation that instructs npm install react-router-dom is outdated and will fail on the current version . The package is now…
SELinux (Security-Enhanced Linux) is a mandatory access control (MAC) system implemented in the Linux kernel. Unlike the traditional discretionary access control (DAC) model, where the file owner decides who can access a resource, SELinux uses a security policy that the system enforces regardless of the user’s identity or the file’s permissions . Every process, file,…
The previous chapter covered resource limits with ulimit, which constrains what a process can consume. This chapter covers the kernel parameters that control how the operating system itself behaves under load. The sysctl command is the interface to the kernel’s tunable parameters. These parameters live in the /proc/sys virtual filesystem and control networking stacks, memory…
The previous chapters covered disk usage and I/O performance. This chapter covers the limits that constrain how much of those resources a process can consume. The ulimit command is the shell builtin that reads and sets the resource limits for the current shell and the processes it spawns. The LFCS exam tests the distinction between…
The previous chapter covered iostat, which reports the I/O activity of a device. This chapter covers iotop, which reports the I/O activity of a process. The distinction is the difference between “the disk is busy” and “this process is making the disk busy.” The LFCS exam tests this diagnostic chain: iostat identifies the saturated device,…
The previous chapters covered process and system monitoring. This chapter covers the tools that answer the question: where is the disk space going? The df command reports the filesystem-level usage: the total size, the used space, and the available space for each mounted filesystem. The du command reports the directory-level usage: the space consumed by…
Using CSS border changes the element’s dimensions and pushes the layout around. Using box-shadow to fake a border keeps the box model intact. I built a free tool that solves this. What it does: Use cases: Privacy:100% client-side. Nothing uploaded. Try it: tools.kandz.me/css-shadow-borders