Add Installing Software

Installing-Software.md

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+# Immutability and Me
+
+When an operating system is immutable, as HalogenOS is, installing software can be difficult. HalogenOS aims to eliminate some of this inconvenience by providing a few different ways to get software.
+
+## Flatpak
+
+Since the root partition is writeable, as well as executable, users can install Flatpak sandboxed applications. This gives the user access to a huge library of useful, tested, and isolated applications without compromising security.
+
+## Distrobox
+
+HalogenOS comes with Distrobox and the gvisor container runtime, which allows users to install isolated Linux distributions in a Docker-like environment, including mediated system calls for tighter security. Eventually, I aim to provide hardened container images, designed to make using applications in containers even more secure.
+
+## Overlays
+
+Developers and power users can submit a public key to the operating system, which will be used to verify read-only "overlays": SquashFS images that are signed by the developer, stored on the encrypted root partition, and mounted read-only over the system partition. Through this, users can add additional binaries, configuration changes, libraries, and services to the system folder.
+
+## AppImages
+
+HalogenOS will hopefully support AppImages, which are bundles of application files that can portably execute applications anywhere.