Migrate ECE to Podman hosts

This section provides guidelines and recommendations for migrating an existing platform to a Podman-based environment. You have an existing ECE installation version >=3.0 and want to migrate all hosts to use Podman as a container runtime. The recommended approach consists of three (3) high-level steps.

Step 1: Upgrade ECE to version >= 3.3.0 following the Upgrade your installation guidelines. Skip this step if your ECE installation is already running a version >= 3.3.0.

Step 2: Prepare an additional RHEL or Rocky Linux VM. We recommend using one additional VM to perform a rolling grow-and-shrink upgrade.

Step 3: Migrate each host one by one from Docker to Podman. This allows you to move workloads from Docker-based hosts to Podman-based ones without downtime. We highly recommend to allocate the additional Podman allocator to the same zone as the Docker allocator you want to replace. The following diagram shows the conceptual steps.

Using Docker or Podman as container runtime is a configuration local to the host. For example, the admin console is not aware which allocator is using Podman. Hence there is no restriction on the migration ordering of the hosts.

When copy-pasting commands, verify that characters like quotes (“) are encoded correctly in the console where you copy the command to.

Steps that run commands starting with sudo can be run as any sudoers user.

Avoid customizing the host Docker path /mnt/data/docker when using SELinux. Otherwise the ECE installer script needs to be adjusted.

Otherwise, when the file content changes, the corresponding user is mentioned as part of the step description.

Make sure you are running a healthy x-node ECE environment ready to be upgraded. All nodes use the Docker container runtime.
Upgrade to ECE 3.3.0+ following the Upgrade your installation guideline. Skip this step if your existing ECE installation already runs ECE >= 3.3.0.
Follow your internal guidelines to add an additional vanilla RHEL (Note that the version must be >= 8.5), or Rocky Linux 8 or 9 VM to your environment.
Verify that required traffic from the host added in step 3 is allowed to the primary ECE VM(s). Check the Networking prerequisites and Google Cloud Platform (GCP) guidelines for a list of ports that need to be open. The technical configuration highly depends on the underlying infrastructure.

Example For AWS, allowing traffic between hosts is implemented using security groups.
Identify the host you want to replace with a podman-based host and copy the associated roles.

Example 1 You want to migrate the Docker host 192.168.44.74 with the role Allocator to a podman host. Copy the role allocator.

Example 2 You want to migrate the Docker host 192.168.44.10 with the roles Allocator, Controller, Director, and Proxy to a podman host. Copy the roles allocator, coordinator, director, proxy.

The role Controller in the admin console is called coordinator for the elastic-cloud-enterprise.sh script
Configure the RHEL or Rocky Linux host.
1. Install the OS packages lvm2, iptables, sysstat, and net-tools by executing:
```
sudo dnf install lvm2 iptables sysstat net-tools 
```
  The ECE diagnostic script requires net-tools.
  For RHEL 9 and Rocky Linux 9, also install the containernetworking-plugins package using:
  
  sudo dnf -y install containernetworking-plugins
2. Remove Docker and previously installed podman packages (if previously installed).
```
sudo dnf remove docker docker-ce podman podman-remote containerd.io
```
3. As a sudoers user, edit the /etc/selinux/config file:
  1. If you are not using SELinux, set it to permissive mode:
    
    SELINUX=permissive
  2. If you are using SELinux, set it to enforcing mode:
    
    Avoid customizing the host Docker path /mnt/data/docker when using SELinux. Otherwise the ECE installer script needs to be adjusted.
    
    SELINUX=enforcing
4. Install podman:
  - For RHEL 8 and Rocky Linux, install version 4.*.
    
    sudo dnf install podman-4.* podman-remote-4.*
  - For RHEL 9, install the latest available version 4.* using dnf.
    
    sudo dnf install podman-4.* podman-remote-4.*
5. [This step is for RHEL 9 and Rocky Linux 9 only] Switch the network stack from Netavark to CNI:
  1. If the /etc/containers/containers.conf file does not exist, copy the /usr/share/containers/containers.conf file to the /etc/containers/ directory (for example, using cp /usr/share/containers/containers.conf /etc/containers/).
  2. Open the /etc/containers/containers.conf file. Navigate to the network section and make sure that the network_backend setting is set to cni.
  3. Reboot the system (reboot).
  4. Check that the network stack has changed to cni:
    
    cat /etc/containers/containers.conf [...] [network] network_backend="cni" [...]
6. If podman requires a proxy in your infrastructure setup, modify the /usr/share/containers/containers.conf file and add the HTTP_PROXY and HTTPS_PROXY environment variables in the [engine] section. Please note that multiple env variables in that configuration file exists — use the one in the [engine] section.
  
  Example:
```
[engine]
env = ["HTTP_PROXY=http://{proxy-ip}:{proxy-port}", "HTTPS_PROXY=http://{proxy-ip}:{proxy-port}"]
```
7. Reload systemd configuration
```
sudo systemctl daemon-reload
```
8. Create OS groups, if they do not exist yet
  
  Reference: Users and permissions
```
sudo groupadd elastic
sudo groupadd podman
```
9. Add user elastic to the podman group
  
  Reference: Users and permissions
```
sudo useradd -g "elastic" -G "podman" elastic
```
10. As a sudoers user, add the following line to /etc/sudoers.d/99-ece-users
  
  Reference: Users and permissions
```
elastic ALL=(ALL) NOPASSWD:ALL
```
11. Add the required options to the kernel boot arguments
```
sudo /sbin/grubby --update-kernel=ALL --args='cgroup_enable=memory cgroup.memory=nokmem swapaccount=1'
```
12. Create the directory
```
sudo mkdir -p /etc/systemd/system/podman.socket.d
```
13. As a sudoers user, create the file /etc/systemd/system/podman.socket.d/podman.conf with the following content. Set the correct ownership and permission.
  
  Both ListenStream= and ListenStream=/var/run/docker.sock parameters are required!
  
  File content:
```
[Socket]
ListenStream=
ListenStream=/var/run/docker.sock
SocketMode=770
SocketUser=elastic
SocketGroup=podman
```
  File ownership and permission:
```
sudo chown root:root /etc/systemd/system/podman.socket.d/podman.conf
sudo chmod 0644 /etc/systemd/system/podman.socket.d/podman.conf
```
14. As a sudoers user, create the (text) file /usr/bin/docker with the following content. Verify that the regular double quotes in the text file are used (ASCII code Hex 22)
```
#!/bin/bash
podman-remote --url unix:///var/run/docker.sock "$@"
```
15. Set the file permissions on /usr/bin/docker
```
sudo chmod 0755 /usr/bin/docker
```
16. As a sudoers user, add the following two lines to section [storage] in the file /etc/containers/storage.conf. Verify that those parameters are only defined once. Either remove or comment out potentially existing parameters.
  
  Avoid customizing the host Docker path /mnt/data/docker when using SELinux. Otherwise the ECE installer script needs to be adjusted.
```
runroot = "/mnt/data/docker/runroot/"
graphroot = "/mnt/data/docker"
```
17. Enable podman so that itself and running containers start automatically after a reboot
```
sudo systemctl enable podman.service
sudo systemctl enable podman-restart.service
```
18. Enable the overlay kernel module (check Use the OverlayFS storage driver) that the Podman overlay storage driver uses (check Working with the Container Storage library and tools in Red Hat Enterprise Linux).
  
  In the Docker world there are two overlay drivers, overlay and overlay2. Today most users use the overlay2 driver, so we just use that one, and called it overlay. Refer also to Use the OverlayFS storage driver.
```
echo "overlay" | sudo tee -a /etc/modules-load.d/overlay.conf
```
19. Format the additional data partition
```
sudo mkfs.xfs /dev/nvme1n1
```
20. Create the /mnt/data/ directory used as a mount point
```
sudo install -o elastic -g elastic -d -m 700 /mnt/data
```
21. As a sudoers user, modify the entry for the XFS volume in the /etc/fstab file to add pquota,prjquota. The default filesystem path used by Elastic Cloud Enterprise is /mnt/data.
  
  Replace /dev/nvme1n1 in the following example with the corresponding device on your host, and add this example configuration as a single line to /etc/fstab.
```
/dev/nvme1n1	/mnt/data	xfs	defaults,nofail,x-systemd.automount,prjquota,pquota  0 2
```
22. Restart the local-fs target
```
sudo systemctl daemon-reload
sudo systemctl restart local-fs.target
```
23. Set the permissions on the newly mounted device
```
ls /mnt/data
sudo chown elastic:elastic /mnt/data
```
24. Create the /mnt/data/docker directory for the Docker service storage
  
  Avoid customizing the host Docker path /mnt/data/docker when using SELinux. Otherwise the ECE installer script needs to be adjusted.
```
sudo install -o elastic -g elastic -d -m 700 /mnt/data/docker
```
25. If you want to use FirewallD, please ensure you meet the networking prerequisites. Otherwise, you can disable it with:
```
sudo systemctl disable firewalld
```
  If FirewallD does not exist on your VM, you can skip this step.
26. Configure kernel parameters
```
cat <<EOF | sudo tee -a /etc/sysctl.conf
# Required by Elasticsearch
vm.max_map_count=262144
# enable forwarding so the Docker networking works as expected
net.ipv4.ip_forward=1
# Decrease the maximum number of TCP retransmissions to 5 as recommended for Elasticsearch TCP retransmission timeout.
# See https://www.elastic.co/guide/en/elasticsearch/reference/current/system-config-tcpretries.html
net.ipv4.tcp_retries2=5
# Make sure the host doesn't swap too early
vm.swappiness=1
EOF
```
27. Apply the new sysctl settings
```
sudo sysctl -p
sudo systemctl restart NetworkManager
```
28. As a sudoers user, adjust the system limits. Add the following configuration values to the /etc/security/limits.conf file.
```
*                soft    nofile         1024000
*                hard    nofile         1024000
*                soft    memlock        unlimited
*                hard    memlock        unlimited
elastic          soft    nofile         1024000
elastic          hard    nofile         1024000
elastic          soft    memlock        unlimited
elastic          hard    memlock        unlimited
elastic          soft    nproc          unlimited
elastic          hard    nproc          unlimited
root             soft    nofile         1024000
root             hard    nofile         1024000
root             soft    memlock        unlimited
```
29. NOTE: This step is optional if the Docker registry doesn’t require authentication.
  
  Authenticate the elastic user to pull images from the Docker registry you use, by creating the file /home/elastic/.docker/config.json. This file needs to be owned by the elastic user. If you are using a user name other than elastic, adjust the path accordingly.
  
  Example: In case you use docker.elastic.co, the file content looks like as follows:
```
{
 "auths": {
   "docker.elastic.co": {
     "auth": "<auth-token>"
   }
 }
}
```
30. Restart the podman service by running this command:
```
sudo systemctl daemon-reload
sudo systemctl restart podman
```
31. Reboot the RHEL host
```
sudo reboot
```
Use the ECE installer script together with the --podman flag to add the additional host as a podman-based host.

Refer to the official Install Elastic Cloud Enterprise on an additional host and Install ECE online documentation to adapt the command line parameters to your environment including fetching the role token.

JVM heap sizes describes recommended JVM options.

Important while running ./elastic-cloud-enterprise.sh
- Make sure you use --podman on the podman host.
- Make sure you use --selinux on the Podman host if SELinux runs in enforcing mode.
- To fetch a role token following the Generate Roles Tokens guidelines, you need to send a JSON token to the admin console. Double check the correct format of the roles. Roles are a list of individual strings in quotes, NOT a single string.
  
  For example 1, the JSON object is as follows:
```
'{ "persistent": true, "roles": [ "allocator" ] }'
```
  For example 2, the JSON object is as follows:
```
'{ "persistent": true, "roles": [ "allocator","coordinator","director","proxy" ] }'
```
- The ECE version of the additional host must be the same as the version used in step 2. Use --cloud-enterprise-version VERSION_NAME to specify the correct version.
- To easily identify the podman allocator, apply a tag to the additional host, for example containerengine:podman. The podman allocator is needed as the “target allocator” when you later move instances from the Docker allocator to the podman allocator. For example, use --allocator-tags containerengine:podman.
- Make sure to apply the roles as copied in step 5 to the additional host. The value for the --roles flag is a single string.
  
  For example 1 in step 4, use --roles "allocator"
  
  For example 2 in step 4, use --roles "allocator,coordinator,director,proxy"
- Add the new host to the same availability zone as the Docker host you want to replace. Use the --availability-zone <zone> flag.
Login to admin console

Verify that the new podman host has the same roles (same coloring of the hexagon) as the Docker host you want to replace.

The following screenshot shows the state where the correct roles have been applied. Both hosts in ece-zone-1 have the same color.

The following screenshot shows the state where incorrect roles have been applied. The hosts in ece-zone-1 do not have the same coloring.
Put the docker-based allocator you want to replace with a podman allocator in maintenance mode by following the Enable Maintenance Mode documentation.

As an alternative, use the Start maintenance mode API.
Move all instances from the Docker allocator to the podman allocator by following the Move Nodes From Allocators documentation.

Make sure to specify the target podman allocator using the option “Set target allocators”.

If you move admin console instances, you might update the URL in the browser before continuing with step 11.

As an alternative, use the Move clusters API.

To identifying the correct target allocator, the following APIs might be helpful:
- Get allocators
- Get allocator metadata
```
{
  "allocator_id": "192.168.44.17",
  "zone_id": "ece-zone-1",
  "host_ip": "192.168.44.17",
  "public_hostname": "192.168.44.17",
  "capacity": {
      "memory": {
          "total": 26000,
          "used": 0
      }
  },
  "settings": {},
  "instances": [],
  "metadata": [
      { 
          "key": "containerengine",
          "value": "podman"
      }
  ]
}
```
  If allocators are tagged as mentioned in step 7, the metadata section of the Get allocators API should contain the tag.
  
  This information allows you to determine what allocators are running on top of podman (automated way)
Remove the Docker allocator by following the Delete Hosts guidelines.

As an alternative, use the Delete Runner API.

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