Update Sysbox-EE README file, and point to Sysbox docs.

Signed-off-by: Cesar Talledo <ctalledo@nestybox.com>

Author: ctalledo

README.md

@@ -1,29 +1,26 @@
-# Sysbox Documentation
+# Sysbox-EE Documentation
 
-This directory contains the Sysbox documentation for both
+Sysbox-EE is a drop-in replacement for Sysbox, meaning that it's installed and
+used in the same way.
 
-- **Sysbox Community Edition (Sysbox-CE)**
-- **Sysbox Enterprise Edition (Sysbox-EE)**
-
-In general, the features and limitations described in these docs apply equally
-to Sysbox-CE and Sysbox-EE.
+For this reason, the documents in the Sysbox repo apply equally to Sysbox-EE.
 
 Features that are specific to Sysbox-EE are tagged with **"Sysbox-EE Feature
 Highlight"**.
 
 Features that appear in a particular Sysbox release are flagged in the docs with
-the release tag (e.g., "**\[ +v0.1.2 ]**" indicates the feature appeared in
+the release tag (e.g., "**\[ v0.1.2+ ]**" indicates the feature appeared in
 Sysbox release v0.1.2 and beyond).
 
 ## Documents
 
 - [Sysbox Distro Compatibility doc](distro-compat.md)
 
-  - Shows Linux distros supported by Sysbox.
+  - Shows Linux distros supported by Sysbox and Sysbox-EE.
 
 - [Sysbox Quick Start Guide](quickstart/README.md)
 
-  - Start here if new to Sysbox; has lots of examples on how to use it.
+  - Start here if new to Sysbox / Sysbox-EE; has lots of examples on how to use it.
 
 - [Sysbox User Guide](user-guide/README.md)
 

docs/README.md

@@ -1,111 +1,30 @@
-# Sysbox Distro Compatibility
+# Sysbox-EE Distro Compatibility
 
 ## Contents
 
-- [Supported Linux Distros](#supported-linux-distros)
-- [Supported Package](#sysbox-package)
-- [Sysbox Operational Modes](#Sysbox-Operational-Modes)
-- [Kernel Upgrade Procedures](#Kernel-Upgrade-Procedures)
+-   [Supported Linux Distros](#supported-linux-distros)
+-   [Kernel Upgrade Procedures](#kernel-upgrade-procedures)
 
 ## Supported Linux Distros
 
-Sysbox relies on functionality that is only present in recent Linux kernels.
+The following table summarizes the supported Linux distros, the installation
+methods supported, and any other requirements:
 
-In Ubuntu's case, these requirements are met starting with Kernel 5.0. For
-the rest of the Sysbox's supported distributions, Kernel 5.5+ is required.
+| Distro / Release      | Package Install | K8s Install | Kernel Upgrade | Other |
+| --------------------- | :-------------: | :---------: | :----: | :----: |
+| Ubuntu Bionic (18.04) | ✓ | ✓ | [Maybe](#ubuntu-kernel-upgrade) | |
+| Ubuntu Focal  (20.04) | ✓ | ✓ | No                              | |
+| Debian Buster (10)    | ✓ |   | [Yes](#debian-kernel-upgrade)   | |
+| Debian Bullseye (11)  | ✓ |   | No                              | |
+| Flatcar               | N/A |   | No                            | More details [here](https://github.com/nestybox/sysbox-flatcar-preview) |
 
-The following table summarizes the Linux distributions being supported, as well
-as the operational modes utilized to manage the [user-namespace ID mappings](user-guide/security.md#user-namespace-id-mapping)
-(i.e. `automatic` vs `directed`).
+**NOTES:**
 
-For scenarios where a kernel upgrade is required, refer to the corresponding
-upgrade procedure further below.
+-   "Package install" means a Sysbox-EE package is available for that distro. See [here](../README.md#installation) for more.
 
-<p align="center">
-    <img alt="sysbox" src="figures/distro-support-matrix.png" width="1000x" />
-</p>
+-   "K8s-install" means you can deploy Sysbox-EE on a Kubernetes worker node based on that distro. See [here](../README.md#installation) for more.
 
-- Note 1: Ubuntu Bionic requires no kernel upgrade in scenarios where relatively
-  recent releases have been installed (i.e. 18.04.4+). If that's not the
-  case, user will need to upgrade the kernel. Refer to [Ubuntu's kernel-upgrade](#Ubuntu-Kernel-Upgrade)
-  procedure for details.
-
-- Note 2: Debian Bullseye (11) requires that the Linux kernel be booted with cgroups
-  v1, as Sysbox does not yet support cgroups v2 (the latter is the default in latest
-  Debian kernels). We will be adding support for cgroups v2 in Sysbox very soon.
-  To boot the Debian kernel with cgroups v1, set kernel parameter
-  `systemd.unified_cgroup_hierarchy=0` as follows and reboot the kernel.
-
-  ```console
-  $ sudo sh -c 'echo GRUB_CMDLINE_LINUX="systemd.unified_cgroup_hierarchy=0" >> /etc/default/grub'
-  $ sudo update-grub
-  ```
-
-- Note 3: Fedora 31 requires no kernel upgrade assuming that user is running a recent
-  installation (i.e. kernel 5.5+ is deployed). Otherwise, a kernel-upgrade will be
-  expected. Refer to [Fedora's kernel-upgrade](#Fedora-kernel-upgrade) procedure for
-  details.
-
-- Note 4: Same as Debian Bullseye's case, Fedora >= 31 also requires that the Linux
-  kernel be booted with cgroups v1. To boot the Fedora kernel with cgroups v1, set
-  kernel parameter `systemd.unified_cgroup_hierarchy=0` as follows and reboot the
-  kernel.
-
-  ```console
-  sudo dnf install grubby
-  sudo grubby --update-kernel=ALL --args="systemd.unified_cgroup_hierarchy=0"
-  ```
-
-## Sysbox Package
-
-We are currently offering the [Sysbox packages](https://github.com/nestybox/sysbox/releases)
-for Ubuntu and Debian distributions. This means that for other distros you must [build and install Sysbox from source](https://github.com/nestybox/sysbox/blob/master/docs/developers-guide/build.md).
-It's pretty easy though, since the Sysbox Makefile has targets that automate this process.
-The build occurs entirely inside a container, so it won't mess up your host.
-
-We are working on creating packaged versions for the other supported distros, and
-expect to have them soon (ETA summer 2021).
-
-## Sysbox Operational Modes
-
-The Sysbox runtime relies on the kernel's user-namespace feature to secure
-system containers. There are two approaches utilized by Sysbox to manage the
-creation of these user-namespaces: `automatic` and `directed`.
-
-It is important to highlight that this operational mode is per individual
-container. That is, a container-manager (e.g. Docker, K8s/Cri-o, Podman, etc)
-could instruct Sysbox to operate in `directed` mode for any given container.
-
-What follows is a high-level description of what each of these modes accomplish;
-refer to the [user-guide](./user-guide/security.md#user-namespace-id-mapping) for
-more details.
-
-### Automatic userns ID mapping
-
-In this mode Sysbox automatically allocates the ID mappings to be used by the
-container. By doing this, Sysbox enforces strong container isolation without
-requiring the higher level container-manager to do this explicitly (e.g. without
-enabling `userns-remap` mode in Docker).
-
-Sysbox will only attempt to operate in this mode if the received container
-specification omits ID mappings configuration.
-
-Note that this mode requires the presence of the `shiftfs` kernel module, which
-currently is only available on the Ubuntu Linux distribution -- with the exception
-of Ubuntu-cloud images deployed in some Cloud Providers.
-
-### Directed userns ID mapping
-
-In this mode Sysbox relies on the container-manager selecting the desired ID
-mappings.
-
-In Docker's case this is accomplished by enabling the `userns-remap` feature
-which, even though imposes certain [restrictions](https://docs.docker.com/engine/security/userns-remap/#user-namespace-known-limitations),
-does not require `shiftfs` and therefore allows Sysbox support in a larger
-number of distributions.
-
-Refer to the Sysbox [installation guide](./user-guide/install.md#docker-userns-remap)
-for more details.
+-   "Kernel upgrade" means a kernel upgrade may be required (Sysbox-EE requires a fairly new kernel). See [below](#kernel-upgrade-procedures) for more.
 
 ## Kernel Upgrade Procedures
 
@@ -125,7 +44,7 @@ $ sudo shutdown -r now
 
 This one is only required when running Debian Buster.
 
-```
+```console
 $ # Allow debian-backports utilization ...
 
 $ echo deb http://deb.debian.org/debian buster-backports main contrib non-free | sudo tee /etc/apt/sources.list.d/buster-backports.list
@@ -138,34 +57,3 @@ $ sudo shutdown -r now
 ```
 
 Refer to this [link](https://wiki.debian.org/HowToUpgradeKernel) for more details.
-
-### Fedora Kernel Upgrade
-
-This is only applicable to Fedora 31 release; more recent releases already
-include 5.5+ kernels.
-
-```
-$ sudo dnf config-manager --set-enabled kernel-vanilla-mainline
-
-$ sudo dnf update
-
-$ sudo shutdown -r now
-```
-
-Refer to this [link](https://www.cloudinsidr.com/content/how-to-upgrade-the-linux-kernel-in-fedora-29/) for more details.
-
-### CentOS Kernel Upgrade
-
-Applicable to CentOS 8 release.
-
-```
-$ sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
-
-$ sudo dnf install https://www.elrepo.org/elrepo-release-8.0-2.el8.elrepo.noarch.rpm
-
-$ sudo dnf --enablerepo=elrepo-kernel install kernel-ml
-
-$ sudo shutdown -r now
-```
-
-Refer to this [link](https://vitux.com/how-to-upgrade-the-kernel-on-centos-8-0/) for more details.