The SSH is the Secure Shell, and it is the protocol that lets one machine reach another over an untrusted network. It is the tool that turns a remote server into a shell, and it is the tool that moves files between the two. The SSH is the modern replacement for the telnet, the rlogin,…
The previous chapter covered the firewall’s concepts: the netfilter’s hooks, the tables, the chains, the connection’s tracking, and the default’s policy. This chapter covers the two front-ends that make the firewall’s configuration practical: ufw and firewalld. The two are the wrappers around the kernel’s netfilter, and each simplifies the rule’s management. The ufw is the…
A firewall is the control point between the trusted and the untrusted. It inspects the packets that cross the boundary, and it decides which ones pass and which ones are dropped. Every server that faces the internet has a firewall, and every host that runs the sensitive services has one. The firewall is the first…
A port is a number that identifies a service on a host. The web server listens on the 80 or the 443, the SSH daemon listens on the 22, the database listens on the 5432. When a connection arrives, the kernel uses the port to route the packet to the right process. The two commands…
When a network connection fails, the question is where it failed. Is the interface up? Is the gateway reachable? Is the DNS resolving? Is the remote host responding? The two commands that answer the reachability questions are ping and traceroute. The ping sends an ICMP echo request and reports whether the reply comes back, how…
The previous chapter covered standalone components and the bootstrap without NgModules. This chapter covers the other two building blocks that the standalone model made first-class: the standalone directive and the standalone pipe. A directive adds behavior to an element, and a pipe transforms a value in the template. Both followed the same evolution as the…
Standalone components are Angular’s answer to the boilerplate that NgModules required for every application. Before them, every component had to be declared in an NgModule, every directive had to be exported from a shared module, and every lazy-loaded route needed its own module. The standalone flag flips the model: a component declares its own dependencies…
The previous chapter covered the provider recipes — the four use* types, the multi-providers, the provideX functions. This chapter covers where the providers live and how long they live. A provider’s scope is the part of the application that resolves the token to that provider, and a provider’s lifecycle is when the instance is created…
In Angular 54 through 56, the DI’s foundation was covered: the injector hierarchy, the injection tokens, the providers, and the hierarchical resolution. This chapter is the practical companion — the recipes. A provider is the recipe that tells the injector what to create for a token. The four forms — useClass, useValue, useFactory, useExisting —…
Angular’s dependency injection is not a flat container. It is a tree of injectors, and the tree mirrors the application’s structure — the component tree, the route tree, the lazy-loaded module tree. When a component asks for a dependency, the injector at that component tries to satisfy the request; if it cannot, it delegates to…