k3s/docs/sharing-clusters.md

# Sharing Cluster Access

Client access to a running kubernetes cluster can be shared by copying
the `kubectl` client config bundle ([.kubeconfig](kubeconfig-file.md)).
This config bundle lives in `$HOME/.kube/.kubeconfig`, and is generated
by `cluster/kube-up.sh`. Sample steps for sharing `.kubeconfig` below.

**1. Create a cluster**
```bash
cluster/kube-up.sh
```
**2. Copy .kubeconfig to new host**
```bash
scp $HOME/.kube/.kubeconfig user@remotehost:/path/to/.kubeconfig
```

**3. On new host, make copied `.kubeconfig` available to `kubectl`**

* Option A: copy to default location
```bash
mv /path/to/.kubeconfig $HOME/.kube/.kubeconfig
```
* Option B: copy to working directory (from which kubectl is run)
```bash
mv /path/to/.kubeconfig $PWD
```
* Option C: manually pass `.kubeconfig` location to `.kubectl`
```bash
# via environment variable
export KUBECONFIG=/path/to/.kubeconfig

# via commandline flag
kubectl ... --kubeconfig=/path/to/.kubeconfig
```

## Manually Generating `.kubeconfig`

`.kubeconfig` is generated by `kube-up` but you can generate your own
using (any desired subset of) the following commands.

```bash
# create kubeconfig entry
kubectl config set-cluster $CLUSTER_NICK
    --server=https://1.1.1.1 \
    --certificate-authority=/path/to/apiserver/ca_file \
    --embed-certs=true \
    # Or if tls not needed, replace --certificate-authority and --embed-certs with
    --insecure-skip-tls-verify=true
    --kubeconfig=/path/to/standalone/.kubeconfig

# create user entry
kubectl config set-credentials $USER_NICK
    # basic auth credentials, generated on kube master
    --username=$username \
    --password=$password \
    # use either username|password or token, not both
    --token=$token \
    --client-certificate=/path/to/crt_file \
    --client-key=/path/to/key_file \
    --embed-certs=true
    --kubeconfig=/path/to/standalone/.kubeconfig

# create context entry
kubectl config set-context $CONTEXT_NAME --cluster=$CLUSTER_NICKNAME --user=$USER_NICK
```
Notes:
* The `--embed-certs` flag is needed to generate a standalone
`.kubeconfig`, that will work as-is on another host.
* `--kubeconfig` is both the preferred file to load config from and the file to
save config too. In the above commands the `--kubeconfig` file could be
omitted if you first run
```bash
export KUBECONFIG=/path/to/standalone/.kubeconfig
```
* The ca_file, key_file, and cert_file referrenced above are generated on the
kube master at cluster turnup. They can be found on the master under
`/srv/kubernetes`. Basic auth/token are also generated on the kube master.

For more details on `.kubeconfig` see [kubeconfig-file.md](kubeconfig-file.md),
and/or run `kubectl config -h`.

## Merging `.kubeconfig` Example

`kubectl` loads and merges config from the following locations (in order)

1. `--kubeconfig=path/to/kubeconfig` commandline flag
2. `KUBECONFIG=path/to/kubeconfig` env variable
3. `$PWD/.kubeconfig`
4. `$HOME/.kube/.kubeconfig`

If you create clusters A, B on host1, and clusters C, D on host2, you can
make all four clusters available on both hosts by running

```bash
# on host2, copy host1's default kubeconfig, and merge it from env
scp host1:/path/to/home1/.kube/.kubeconfig path/to/other/.kubeconfig

export $KUBECONFIG=path/to/other/.kubeconfig

# on host1, copy host2's default kubeconfig and merge it from env
scp host2:/path/to/home2/.kube/.kubeconfig path/to/other/.kubeconfig

export $KUBECONFIG=path/to/other/.kubeconfig
```
Detailed examples and explanation of `.kubeconfig` loading/merging rules can be found in [kubeconfig-file.md](https://github.com/GoogleCloudPlatform/kubernetes/blob/master/docs/kubeconfig-file.md).