CLOS-4525: Add Docker on CloudLinux documentation page

docs/.vuepress/config-client/sidebar.ts

@@ -65,6 +65,7 @@ export default {
                 "/cloudlinuxos/alt-ea_packages/",
                 "/cloudlinuxos/control_panel_integration/",
                 "/cloudlinuxos/cloudlinux_os_kernel/",
+                "/cloudlinuxos/docker/",
                 "/cloudlinuxos/for_cloudlinux_partners/",
                 "/cloudlinuxos/deprecated/"
             ]

docs/cloudlinuxos/docker/README.md

@@ -0,0 +1,126 @@
+# Docker on CloudLinux
+
+[[toc]]
+
+## Introduction
+
+A common question is: **Can Docker be installed with CloudLinux?**
+
+**Docker can run inside CloudLinux**, but CloudLinux cannot run inside Docker.
+
+Docker Engine and local containers are supported on **CloudLinux OS 8+**.
+
+:::warning CloudLinux OS 7
+Docker's official RHEL repository no longer publishes packages for RHEL 7 (`https://download.docker.com/linux/rhel/7/x86_64/stable/` unavailable), so neither method below works on CL7 as-is.
+Two legacy paths still exist - see [CloudLinux OS 7 (legacy)](#cloudlinux-os-7-legacy) below. It's recommended to upgrade to a newer CloudLinux OS version via [ELevate](/cloudlinuxos/elevate/).
+:::
+
+There are two installation options:
+
+* **Direct installation** - add Docker's RHEL repo and install with `dnf`; no system changes required.
+* **Docker convenience script** - served from [get.docker.com](https://get.docker.com); requires a one-time `os-release` workaround.
+
+This guide describes both.
+
+Note that Docker is **not** in default CloudLinux repos; both methods use Docker's [official RHEL repo](https://docs.docker.com/engine/install/rhel/).
+
+## Method 1: Direct installation (repo + dnf)
+
+Add Docker's RHEL repository and install packages with `dnf`. No change to `/etc/os-release` or any other system file is required.
+
+**Steps:**
+
+```bash
+# Add Docker repo (RHEL)
+sudo dnf -y install dnf-plugins-core
+sudo dnf config-manager --add-repo https://download.docker.com/linux/rhel/docker-ce.repo
+
+# Install and start
+sudo dnf install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
+sudo systemctl enable --now docker
+
+# Verify
+sudo docker run --rm hello-world
+```
+
+:::tip Notes
+* No workaround needed; leave `ID=cloudlinux` in `/etc/os-release` as-is.
+* You control exactly which packages and repo are added.
+:::
+
+## Method 2: Docker convenience script (get.docker.com)
+
+Use the official [Docker convenience script](https://get.docker.com) (e.g. `curl -fsSL https://get.docker.com | sh`). The script detects the OS via `ID` in `/etc/os-release` and only supports a fixed list of distributions.
+
+CloudLinux is not in that list, so with the default `ID=cloudlinux` the script exits with:
+
+```text
+ERROR: Unsupported distribution 'cloudlinux'
+```
+
+On CloudLinux OS 10, with `ID=almalinux`, the same applies, since `almalinux` is not supported by the script either.
+
+**Workaround:** Temporarily set `ID=centos` in `/etc/os-release` so the script uses the RHEL/CentOS path and adds the Docker CE repo. Revert `ID` after installation.
+
+**Steps:**
+
+1. **Apply the workaround** (one-time, before running the script). Edit `/etc/os-release` and change:
+
+* CloudLinux OS 8 / CloudLinux OS 9: `ID=cloudlinux` -> `ID=centos`
+* CloudLinux OS 10: `ID=almalinux` -> `ID=centos`
+
+2. **Run the script:**
+
+```bash
+curl -fsSL https://get.docker.com | sh
+```
+
+3. **Start Docker** (if the script didn't):
+
+```bash
+sudo systemctl enable --now docker
+```
+
+4. **Verify:**
+
+```bash
+sudo docker run --rm hello-world
+```
+
+:::tip Notes
+* The script has **no option or environment variable** to override or ignore the OS check (only `--version`, `--channel`, `--mirror`, etc.). Without modifying the script, the workaround above is the way to use it on CloudLinux.
+:::
+
+## CloudLinux OS 7 (legacy)
+
+Docker no longer publishes el7 RPMs to its main RHEL repository, but two archive paths remain on `download.docker.com`.
+
+### Option A: Frozen CentOS 7 RPM archive
+
+The CentOS 7 path on `download.docker.com` is served but frozen.
+
+It will not receive future security updates from Docker - use at your own risk.
+
+* Repo file: [`https://download.docker.com/linux/centos/docker-ce.repo`](https://download.docker.com/linux/centos/docker-ce.repo)
+* Package index: [`https://download.docker.com/linux/centos/7/x86_64/stable/Packages/`](https://download.docker.com/linux/centos/7/x86_64/stable/Packages/)
+
+Installation follows the same shape as [Method 1](#method-1-direct-installation-repo-dnf), but with `yum` instead of `dnf` and the CentOS repo file instead of the RHEL one:
+
+```bash
+sudo yum -y install yum-utils
+sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
+sudo yum install -y docker-ce docker-ce-cli containerd.io
+sudo systemctl enable --now docker
+```
+
+### Option B: Docker static binaries
+
+Docker publishes OS-independent static binaries that run on any modern x86_64 Linux kernel (including CloudLinux OS 7's LVE kernel).
+
+* Download index: [`https://download.docker.com/linux/static/stable/x86_64/`](https://download.docker.com/linux/static/stable/x86_64/)
+* Updated alongside main Docker releases
+* Ships `dockerd` and `docker` as standalone binaries - no systemd unit, package-manager integration, or automatic security updates
+
+You will need to write your own systemd unit, manage users/groups, and track upstream releases manually.
+
+See Docker's official [Install Docker Engine from binaries](https://docs.docker.com/engine/install/binaries/) for the procedure.