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Add disable flags documentation

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galal-hussein
2021-04-07 01:00:25 +02:00
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content/k3s/latest/en/installation/_index.md
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@@ -13,6 +13,8 @@ This section contains instructions for installing K3s in various environments. P
[Air-Gap Installation]({{<baseurl>}}/k3s/latest/en/installation/airgap/) details how to set up K3s in environments that do not have direct access to the Internet.
[Disable Components Flags]({{<baseurl>}}/k3s/latest/en/installation/disable-flags/) details how to set up K3s with etcd only nodes and controlplane only nodes
### Uninstalling
If you installed K3s with the help of the `install.sh` script, an uninstall script is generated during installation. The script is created on your node at `/usr/local/bin/k3s-uninstall.sh` (or as `k3s-agent-uninstall.sh`).
content/k3s/latest/en/installation/disable-flags/_index.md
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---
title: "Disable Components Flags"
weight: 60
---
When starting K3s server with --cluster-init it will run all control plane components that includes (api server, controller manager, scheduler, and etcd). However you can run server nodes with certain components and execlude others, the following sectiohs will explain how to do that.
# ETCD Only Nodes
This document assumes you run K3s server with embedded etcd by passing `--cluster-init` flag to the server process.
To run a K3s server with only etcd components you can pass `--disable-api-server --disable-controller-manager --disable-scheduler` flags to k3s, this will result in running a server node with only etcd, for example to run K3s server with those flags:
```
curl -fL https://get.k3s.io | sh -s - server --cluster-init --disable-api-server --disable-controller-manager --disable-scheduler
```
You can join other nodes to the cluster normally after that.
# Disable ETCD
You can also disable etcd from a server node and this will result in a k3s server running control components other than etcd, that can be accomplished by running k3s server with flag `--disable-etcd` for example to join another node with only control components to the etcd node created in the previous section:
```
curl -fL https://get.k3s.io | sh -s - server --token <token> --disable-etcd --server https://<etcd-only-node>:6443
```
The end result will be a two nodes one of them is etcd only node and the other one is controlplane only node, if you check the node list you should see something like the following:
```
kubectl get nodes
NAME STATUS ROLES AGE VERSION
ip-172-31-13-32 Ready etcd 5h39m v1.20.4+k3s1
ip-172-31-14-69 Ready control-plane,master 5h39m v1.20.4+k3s1
```
Note that you can run `kubectl` commands only on the k3s server that has the api running, and you cant run `kubectl` commands on etcd only nodes.
### Re-enabling control components
In both cases you can re-enable any component that you already disabled simply by removing the corresponding flag that disables them, so for example if you want to revert the etcd only node back to a full k3s server with all components you can just remove the following 3 flags `--disable-api-server --disable-controller-manager --disable-scheduler`, so in our example to revert back node `ip-172-31-13-32` to a full k3s server you can just re-run the curl command without the disable flags:
```
curl -fL https://get.k3s.io | sh -s - server --cluster-init
```
you will notice that all components started again and you can run kubectl commands again:
```
kubectl get nodes
NAME STATUS ROLES AGE VERSION
ip-172-31-13-32 Ready control-plane,etcd,master 5h45m v1.20.4+k3s1
ip-172-31-14-69 Ready control-plane,master 5h45m v1.20.4+k3s1
```
Notice that role labels has been re-added to the node `ip-172-31-13-32` with the correct labels (control-plane,etcd,master).
# Add disable flags using the config file
In any of the previous situation you can use the config file instead of running the curl commands with the associated flags, for example to run an etcd only node you can add the following options to the `/etc/rancher/k3s/config.yaml` file:
```
---
disable-api-server: true
disable-controller-manager: true
disable-scheduler: true
cluster-init: true
```
and then start K3s using the curl command without any arguents:
```
curl -fL https://get.k3s.io | sh -
```