Added immutable oses' notes to the knowledge base

knowledge base/fedora silverblue.md

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+# Fedora Silverblue
+
+## TL;DR
+
+Changes to the base layer are executed in a new bootable filesystem root. This means that the system must be rebooted after a package has been layered.
+
+```shell
+# Check for available upgrades.
+rpm-ostree upgrade --check
+
+# Upgrade the system.
+rpm-ostree upgrade
+
+# Install packages.
+rpm-ostree install kmod-nvidia xorg-x11-drv-nvidia
+
+# Override packages.
+rpm-ostree override replace \
+  local/path/to/podman-3.1.2-1.fc34.x86_64.rpm \
+  https://kojipkgs.fedoraproject.org/packages/podman/3.1.2/1.fc34/x86_64/podman-plugins-3.1.2-1.fc34.x86_64.rpm
+
+# Remove packages.
+# Packages will still exist in the undelying base layer, but will not appear
+# in the booted root.
+rpm-ostree override remove nano
+
+# Rollback.
+rpm-ostree rollback
+
+# Make changes to the kernel's boot arguments.
+rpm-ostree kargs \
+  --append=rd.driver.blacklist=nouveau \
+  --append=modprobe.blacklist=nouveau \
+  --append=nvidia-drm.modeset=1
+
+# Preview changes on the current filesystem.
+rpm-ostree ex apply-live
+```
+
+## Package layering
+
+Package layering works by modifying your Silverblue installation by extending the packages from which Silverblue is composed.
+
+Using package layering creates a new _deployment_, or bootable filesystem root which **does not** affect your current root. This means that the system must be rebooted after a package has been layered.
+
+If you don't want to reboot your system to switch to the new deployment, you can use `rpm-ostree ex apply-live` to update the current filesystem and be able to see the changes from the new deployment. It's generally expected that you use package layering sparingly, and use [flatpak]s and [toolbox].
+
+## Further readings
+
+- [User guide]
+- [Flatpak]
+- [Toolbox]
+
+[flatpak]: flatpak.md
+[toolbox]: toolbox.md
+
+[user guide]: https://docs.fedoraproject.org/en-US/fedora-silverblue/

knowledge base/microos.md

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+# OpenSUSE MicroOS
+
+## TL;DR
+
+Every set of changes to the underlying system is executed on a new inactive snapshot, which will be the one the system will boot into on the next reboot.
+
+```shell
+# Upgrade the system.
+sudo transactional-update dup
+pkcon update
+
+# Install a package.
+sudo transactional-update pkg install tlp ntfs-3g fuse-exfat nano
+pkcon install gnu_parallel
+
+# Get a shell on the next snapshot.
+# Lets you use zypper.
+sudo transactional-update shell
+sudo tukit execute bash
+```
+
+## Setting up MicroOS as a desktop OS
+
+See [MicroOS Desktop] for more and updated information.
+
+## Sources
+
+- [MicroOS Desktop]
+
+[microos desktop]: https://opensuse.github.io/openSUSE-docs-revamped-temp/microos_getting_started/

knowledge base/toolbox.md

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+# Toolbox
+
+Runs on top of [Podman].
+
+## TL;DR
+
+```shell
+# List locally available images and containers.
+toolbox list
+toolbox list -c
+
+# Download an OCI image and create a container from it.
+toolbox create
+toolbox create -d rhel -r 8.1
+toolbox create -i registry.fedoraproject.org/fedora-toolbox:35 fedora
+
+# Run a command inside the container without entering it.
+toolbox run ls -la
+toolbox run -d rhel -r 8.1 uptime
+toolbox-run -c fedora cat /etc/os-release
+
+# Get a shell inside the container.
+toolbox enter
+toolbox enter -d fedora -r f35
+toolbox enter rhel
+
+# Remove a container.
+toolbox rm fedora-toolbox-35
+
+# Remove an image.
+toolbox rmi fedora-toolbox:35
+toolbox rmi -af
+```
+
+## Further readings
+
+- [GitHub] page
+- [Podman]
+
+[podman]: podman.md
+
+[github]: https://github.com/containers/toolbox
+
+## Sources
+
+- [Fedora Silverblue]
+
+[fedora silverblue]: https://docs.fedoraproject.org/en-US/fedora-silverblue/toolbox/