Host-level tasks

Adding a host to the cluster
Master host tasks
Node host tasks
etcd tasks

Adding a host to the cluster

For information on adding master or node hosts to a cluster, see the Adding hosts to an existing cluster section in the Install and configuration guide.

Master host tasks

Deprecating a master host

Deprecating a master host removes it from the OpenShift Container Platform environment.

The reasons to deprecate or scale down master hosts include hardware re-sizing or replacing the underlying infrastructure.

Highly available OpenShift Container Platform environments require at least three master hosts and three etcd nodes. Usually, the master hosts are colocated with the etcd services. If you deprecate a master host, you must also deprecate the etcd service on that host.

Ensure that the master and etcd services are always deployed in odd numbers due to the voting mechanisms that take place among those services.

Creating a master host backup

Perform this backup process before any change to the OpenShift Container Platform infrastructure, such as a system update, upgrade, or any other significant modification. Back up data regularly to ensure that recent data is available if a failure occurs.

OpenShift Container Platform files

The master instances run important services, such as the API, controllers. The /etc/origin/master directory stores many important files:

The configuration, the API, controllers, services, and more
Certificates generated by the installation
All cloud provider-related configuration
Keys and other authentication files, such as htpasswd if you use htpasswd
And more

You can customize OpenShift Container Platform services, such as increasing the log level or using proxies. The configuration files are stored in the /etc/sysconfig directory.

Because the masters are also unschedulable nodes, back up the entire /etc/origin directory.

Procedure

You must perform the following steps on each master node.

Create a backup of the master host configuration files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo cp -aR /etc/origin ${MYBACKUPDIR}/etc
$ sudo cp -aR /etc/sysconfig/atomic-* ${MYBACKUPDIR}/etc/sysconfig/

The configuration file is stored in the /etc/sysconfig/atomic-openshift-master-api, and /etc/sysconfig/atomic-openshift-master-controllers directories.

The /etc/origin/master/ca.serial.txt file is generated on only the first master listed in the Ansible host inventory. If you deprecate the first master host, copy the /etc/origin/master/ca.serial.txt file to the rest of master hosts before the process.

Other important files that need to be considered when planning a backup include:

File

Description

/etc/cni/*

Container Network Interface configuration (if used)

/etc/sysconfig/iptables

Where the iptables rules are stored

/etc/sysconfig/docker-storage-setup

The input file for container-storage-setup command

/etc/sysconfig/docker

The docker configuration file

/etc/sysconfig/docker-network

docker networking configuration (i.e. MTU)

/etc/sysconfig/docker-storage

docker storage configuration (generated by container-storage-setup)

/etc/dnsmasq.conf

Main configuration file for dnsmasq

/etc/dnsmasq.d/*

Different dnsmasq configuration files

/etc/sysconfig/flanneld

flannel configuration file (if used)

/etc/pki/ca-trust/source/anchors/

Certificates added to the system (i.e. for external registries)

Create a backup of those files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo mkdir -p ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors
$ sudo cp -aR /etc/sysconfig/{iptables,docker-*,flanneld} \
    ${MYBACKUPDIR}/etc/sysconfig/
$ sudo cp -aR /etc/dnsmasq* /etc/cni ${MYBACKUPDIR}/etc/
$ sudo cp -aR /etc/pki/ca-trust/source/anchors/* \
    ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors/

If a package is accidentally removed or you need to resore a file that is included in an rpm package, having a list of rhel packages installed on the system can be useful.

If you use Red Hat Satellite features, such as content views or the facts store, provide a proper mechanism to reinstall the missing packages and a historical data of packages installed in the systems.

To create a list of the current rhel packages installed in the system:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}
$ rpm -qa | sort | sudo tee $MYBACKUPDIR/packages.txt

If you used the previous steps, the following files are present in the backup directory:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo find ${MYBACKUPDIR} -mindepth 1 -type f -printf '%P\n'
etc/sysconfig/atomic-openshift-master
etc/sysconfig/atomic-openshift-master-api
etc/sysconfig/atomic-openshift-master-controllers
etc/sysconfig/atomic-openshift-node
etc/sysconfig/flanneld
etc/sysconfig/iptables
etc/sysconfig/docker-network
etc/sysconfig/docker-storage
etc/sysconfig/docker-storage-setup
etc/sysconfig/docker-storage-setup.rpmnew
etc/origin/master/ca.crt
etc/origin/master/ca.key
etc/origin/master/ca.serial.txt
etc/origin/master/ca-bundle.crt
etc/origin/master/master.proxy-client.crt
etc/origin/master/master.proxy-client.key
etc/origin/master/service-signer.crt
etc/origin/master/service-signer.key
etc/origin/master/serviceaccounts.private.key
etc/origin/master/serviceaccounts.public.key
etc/origin/master/openshift-master.crt
etc/origin/master/openshift-master.key
etc/origin/master/openshift-master.kubeconfig
etc/origin/master/master.server.crt
etc/origin/master/master.server.key
etc/origin/master/master.kubelet-client.crt
etc/origin/master/master.kubelet-client.key
etc/origin/master/admin.crt
etc/origin/master/admin.key
etc/origin/master/admin.kubeconfig
etc/origin/master/etcd.server.crt
etc/origin/master/etcd.server.key
etc/origin/master/master.etcd-client.key
etc/origin/master/master.etcd-client.csr
etc/origin/master/master.etcd-client.crt
etc/origin/master/master.etcd-ca.crt
etc/origin/master/policy.json
etc/origin/master/scheduler.json
etc/origin/master/htpasswd
etc/origin/master/session-secrets.yaml
etc/origin/master/openshift-router.crt
etc/origin/master/openshift-router.key
etc/origin/master/registry.crt
etc/origin/master/registry.key
etc/origin/master/master-config.yaml
etc/origin/generated-configs/master-master-1.example.com/master.server.crt
...[OUTPUT OMITTED]...
etc/origin/cloudprovider/openstack.conf
etc/origin/node/system:node:master-0.example.com.crt
etc/origin/node/system:node:master-0.example.com.key
etc/origin/node/ca.crt
etc/origin/node/system:node:master-0.example.com.kubeconfig
etc/origin/node/server.crt
etc/origin/node/server.key
etc/origin/node/node-dnsmasq.conf
etc/origin/node/resolv.conf
etc/origin/node/node-config.yaml
etc/origin/node/flannel.etcd-client.key
etc/origin/node/flannel.etcd-client.csr
etc/origin/node/flannel.etcd-client.crt
etc/origin/node/flannel.etcd-ca.crt
etc/pki/ca-trust/source/anchors/openshift-ca.crt
etc/pki/ca-trust/source/anchors/registry-ca.crt
etc/dnsmasq.conf
etc/dnsmasq.d/origin-dns.conf
etc/dnsmasq.d/origin-upstream-dns.conf
etc/dnsmasq.d/node-dnsmasq.conf
packages.txt

If needed, you can compress the files to save space:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo tar -zcvf /backup/$(hostname)-$(date +%Y%m%d).tar.gz $MYBACKUPDIR
$ sudo rm -Rf ${MYBACKUPDIR}

To create any of these files from scratch, the openshift-ansible-contrib repository contains the backup_master_node.sh script, which performs the previous steps. The script creates a directory on the host where you run the script and copies all the files previously mentioned.

The openshift-ansible-contrib script is not supported by Red Hat, but the reference architecture team performs testing to ensure the code operates as defined and is secure.

You can run the script on every master host with:

$ mkdir ~/git
$ cd ~/git
$ git clone https://github.com/openshift/openshift-ansible-contrib.git
$ cd openshift-ansible-contrib/reference-architecture/day2ops/scripts
$ ./backup_master_node.sh -h

Backing up etcd

When you back up etcd, you must back up both the etcd configuration files and the etcd data.

Backing up etcd configuration files

The etcd configuration files to be preserved are all stored in the /etc/etcd directory of the instances where etcd is running. This includes the etcd configuration file (/etc/etcd/etcd.conf) and the required certificates for cluster communication. All those files are generated at installation time by the Ansible installer.

Procedure

For each etcd member of the cluster, back up the etcd configuration.

$ ssh master-0
# mkdir -p /backup/etcd-config-$(date +%Y%m%d)/
# cp -R /etc/etcd/ /backup/etcd-config-$(date +%Y%m%d)/

The certificates and configuration files on each etcd cluster member are unique.

Backing up etcd data

Prerequisites

The OpenShift Container Platform installer creates aliases to avoid typing all the flags named etcdctl2 for etcd v2 tasks and etcdctl3 for etcd v3 tasks.

However, the etcdctl3 alias does not provide the full endpoint list to the etcdctl command, so the --endpoints option with all the endpoints must be provided.

Before backing up etcd:

etcdctl binaries should be available or, in containerized installations, the rhel7/etcd container should be available
Ensure connectivity with the etcd cluster (port 2379/tcp)
Ensure the proper certificates to connect to the etcd cluster

Procedure

While the etcdctl backup command is used to perform the backup, etcd v3 has no concept of a backup. Instead, you either take a snapshot from a live member with the etcdctl snapshot save command or copy the member/snap/db file from an etcd data directory.

The etcdctl backup command rewrites some of the metadata contained in the backup, specifically, the node ID and cluster ID, which means that in the backup, the node loses its former identity. To recreate a cluster from the backup, you create a new, single-node cluster, then add the rest of the nodes to the cluster. The metadata is rewritten to prevent the new node from joining an existing cluster.

Back up the etcd data:

If you use the v2 API, take the following actions:

Stop all etcd services:
```
# systemctl stop etcd.service
```

Create the etcd data backup and copy the etcd db file:

# mkdir -p /backup/etcd-$(date +%Y%m%d)
# etcdctl2 backup \
    --data-dir /var/lib/etcd \
    --backup-dir /backup/etcd-$(date +%Y%m%d)
# cp /var/lib/etcd/member/snap/db /backup/etcd-$(date +%Y%m%d)

Start all etcd services:
```
# systemctl start etcd.service
```

If you use the v3 API, run the following commands:

Because clusters upgraded from previous versions of OpenShift Container Platform might contain v2 data stores, back up both v2 and v3 datastores.
1. Back up etcd v3 data:
  # systemctl show etcd --property=ActiveState,SubState # mkdir -p /backup/etcd-$(date +%Y%m%d) # etcdctl3 snapshot save */backup/etcd-$(date +%Y%m%d)*/db Snapshot saved at /backup/etcd-<date>/db
2. Back up etcd v2 data:
  # systemctl stop etcd.service # etcdctl2 backup \ --data-dir /var/lib/etcd \ --backup-dir /backup/etcd-$(date +%Y%m%d) # cp /var/lib/etcd/member/snap/db /backup/etcd-$(date +%Y%m%d) # systemctl start etcd.service
  The etcdctl snapshot save command requires the etcd service to be running.
  
  In these commands, a /backup/etcd-<date>/ directory is created, where <date> represents the current date, which must be an external NFS share, S3 bucket, or any external storage location.
  
  In the case of an all-in-one cluster, the etcd data directory is located in the /var/lib/origin/openshift.local.etcd directory.

Deprecating a master host

Master hosts run important services, such as the OpenShift Container Platform API and controllers services. In order to deprecate a master host, these services must be stopped.

The OpenShift Container Platform API service is an active/active service, so stopping the service does not affect the environment as long as the requests are sent to a separate master server. However, the OpenShift Container Platform controllers service is an active/passive service, where the services leverage etcd to decide the active master.

Deprecating a master host in a multi-master architecture includes removing the master from the load balancer pool to avoid new connections attempting to use that master. This process depends heavily on the load balancer used. The steps below show the details of removing the master from haproxy. In the event that OpenShift Container Platform is running on a cloud provider, or using a F5 appliance, see the specific product documents to remove the master from rotation.

Procedure

Remove the backend section in the /etc/haproxy/haproxy.cfg configuration file. For example, if deprecating a master named master-0.example.com using haproxy, ensure the host name is removed from the following:
```
backend mgmt8443
    balance source
    mode tcp
    # MASTERS 8443
    server master-1.example.com 192.168.55.12:8443 check
    server master-2.example.com 192.168.55.13:8443 check
```
Then, restart the haproxy service.
```
$ sudo systemctl restart haproxy
```

Once the master is removed from the load balancer, disable the API and controller services:

$ sudo systemctl disable --now atomic-openshift-master-api
$ sudo systemctl disable --now atomic-openshift-master-controllers

Because the master host is a unschedulable OpenShift Container Platform node, follow the steps in the Deprecating a node host section.

Remove the master host from the [masters] and [nodes] groups in the /etc/ansible/hosts Ansible inventory file to avoid issues if running any Ansible tasks using that inventory file.

Deprecating the first master host listed in the Ansible inventory file requires extra precautions.

The kubernetes service includes the master host IPs as endpoints. To verify that the master has been properly deprecated, review the kubernetes service output and see if the deprecated master has been removed:

$ oc describe svc kubernetes -n default
Name:			kubernetes
Namespace:		default
Labels:			component=apiserver
			provider=kubernetes
Annotations:		<none>
Selector:		<none>
Type:			ClusterIP
IP:			10.111.0.1
Port:			https	443/TCP
Endpoints:		192.168.55.12:8443,192.168.55.13:8443
Port:			dns	53/UDP
Endpoints:		192.168.55.12:8053,192.168.55.13:8053
Port:			dns-tcp	53/TCP
Endpoints:		192.168.55.12:8053,192.168.55.13:8053
Session Affinity:	ClientIP
Events:			<none>

After the master has been successfully deprecated, the host where the master was previously running can be safely deleted.

Removing an etcd host

If an etcd host fails beyond restoration, remove it from the cluster.

Steps to be performed on all masters hosts

Procedure

Remove each other etcd host from the etcd cluster. Run the following command for each etcd node:

# etcdctl -C https://<surviving host IP address>:2379 \
  --ca-file=/etc/etcd/ca.crt     \
  --cert-file=/etc/etcd/peer.crt     \
  --key-file=/etc/etcd/peer.key member remove <failed member ID>

Restart the master API service on every master:
```
# systemctl restart atomic-openshift-master-api
```
Or, if using a single master cluster installation:
```
# systemctl restart atomic-openshift-master
```

Steps to be performed in the current etcd cluster

Procedure

Remove the failed host from the cluster:

# etcdctl2 cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
failed to check the health of member 8372784203e11288 on https://192.168.55.21:2379: Get https://192.168.55.21:2379/health: dial tcp 192.168.55.21:2379: getsockopt: connection refused
member 8372784203e11288 is unreachable: [https://192.168.55.21:2379] are all unreachable
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

# etcdctl2 member remove 8372784203e11288 (1)
Removed member 8372784203e11288 from cluster

# etcdctl2 cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

1	The `remove` command requires the etcd ID, not the hostname.

To ensure the etcd configuration does not use the failed host when the etcd service is restarted, modify the /etc/etcd/etcd.conf file on all remaining etcd hosts and remove the failed host in the value for the ETCD_INITIAL_CLUSTER variable:
```
# vi /etc/etcd/etcd.conf
```
For example:
```
ETCD_INITIAL_CLUSTER=master-0.example.com=https://192.168.55.8:2380,master-1.example.com=https://192.168.55.12:2380,master-2.example.com=https://192.168.55.13:2380
```
becomes:
```
ETCD_INITIAL_CLUSTER=master-0.example.com=https://192.168.55.8:2380,master-1.example.com=https://192.168.55.12:2380
```
Restarting the etcd services is not required, because the failed host is removed using etcdctl.
Modify the Ansible inventory file to reflect the current status of the cluster and to avoid issues when re-running a playbook:
```
[OSEv3:children]
masters
nodes
etcd

... [OUTPUT ABBREVIATED] ...

[etcd]
master-0.example.com
master-1.example.com
```
If you are using Flannel, modify the flanneld service configuration located at /etc/sysconfig/flanneld on every host and remove the etcd host:
```
FLANNEL_ETCD_ENDPOINTS=https://master-0.example.com:2379,https://master-1.example.com:2379,https://master-2.example.com:2379
```
Restart the flanneld service:
```
# systemctl restart flanneld.service
```

Creating a master host backup

OpenShift Container Platform files

The master instances run important services, such as the API, controllers. The /etc/origin/master directory stores many important files:

The configuration, the API, controllers, services, and more
Certificates generated by the installation
All cloud provider-related configuration
Keys and other authentication files, such as htpasswd if you use htpasswd
And more

You can customize OpenShift Container Platform services, such as increasing the log level or using proxies. The configuration files are stored in the /etc/sysconfig directory.

Because the masters are also unschedulable nodes, back up the entire /etc/origin directory.

Procedure

You must perform the following steps on each master node.

Create a backup of the master host configuration files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo cp -aR /etc/origin ${MYBACKUPDIR}/etc
$ sudo cp -aR /etc/sysconfig/atomic-* ${MYBACKUPDIR}/etc/sysconfig/

The configuration file is stored in the /etc/sysconfig/atomic-openshift-master-api, and /etc/sysconfig/atomic-openshift-master-controllers directories.

Other important files that need to be considered when planning a backup include:

File

Description

/etc/cni/*

Container Network Interface configuration (if used)

/etc/sysconfig/iptables

Where the iptables rules are stored

/etc/sysconfig/docker-storage-setup

The input file for container-storage-setup command

/etc/sysconfig/docker

The docker configuration file

/etc/sysconfig/docker-network

docker networking configuration (i.e. MTU)

/etc/sysconfig/docker-storage

docker storage configuration (generated by container-storage-setup)

/etc/dnsmasq.conf

Main configuration file for dnsmasq

/etc/dnsmasq.d/*

Different dnsmasq configuration files

/etc/sysconfig/flanneld

flannel configuration file (if used)

/etc/pki/ca-trust/source/anchors/

Certificates added to the system (i.e. for external registries)

Create a backup of those files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo mkdir -p ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors
$ sudo cp -aR /etc/sysconfig/{iptables,docker-*,flanneld} \
    ${MYBACKUPDIR}/etc/sysconfig/
$ sudo cp -aR /etc/dnsmasq* /etc/cni ${MYBACKUPDIR}/etc/
$ sudo cp -aR /etc/pki/ca-trust/source/anchors/* \
    ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors/

If a package is accidentally removed or you need to resore a file that is included in an rpm package, having a list of rhel packages installed on the system can be useful.

To create a list of the current rhel packages installed in the system:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}
$ rpm -qa | sort | sudo tee $MYBACKUPDIR/packages.txt

If you used the previous steps, the following files are present in the backup directory:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo find ${MYBACKUPDIR} -mindepth 1 -type f -printf '%P\n'
etc/sysconfig/atomic-openshift-master
etc/sysconfig/atomic-openshift-master-api
etc/sysconfig/atomic-openshift-master-controllers
etc/sysconfig/atomic-openshift-node
etc/sysconfig/flanneld
etc/sysconfig/iptables
etc/sysconfig/docker-network
etc/sysconfig/docker-storage
etc/sysconfig/docker-storage-setup
etc/sysconfig/docker-storage-setup.rpmnew
etc/origin/master/ca.crt
etc/origin/master/ca.key
etc/origin/master/ca.serial.txt
etc/origin/master/ca-bundle.crt
etc/origin/master/master.proxy-client.crt
etc/origin/master/master.proxy-client.key
etc/origin/master/service-signer.crt
etc/origin/master/service-signer.key
etc/origin/master/serviceaccounts.private.key
etc/origin/master/serviceaccounts.public.key
etc/origin/master/openshift-master.crt
etc/origin/master/openshift-master.key
etc/origin/master/openshift-master.kubeconfig
etc/origin/master/master.server.crt
etc/origin/master/master.server.key
etc/origin/master/master.kubelet-client.crt
etc/origin/master/master.kubelet-client.key
etc/origin/master/admin.crt
etc/origin/master/admin.key
etc/origin/master/admin.kubeconfig
etc/origin/master/etcd.server.crt
etc/origin/master/etcd.server.key
etc/origin/master/master.etcd-client.key
etc/origin/master/master.etcd-client.csr
etc/origin/master/master.etcd-client.crt
etc/origin/master/master.etcd-ca.crt
etc/origin/master/policy.json
etc/origin/master/scheduler.json
etc/origin/master/htpasswd
etc/origin/master/session-secrets.yaml
etc/origin/master/openshift-router.crt
etc/origin/master/openshift-router.key
etc/origin/master/registry.crt
etc/origin/master/registry.key
etc/origin/master/master-config.yaml
etc/origin/generated-configs/master-master-1.example.com/master.server.crt
...[OUTPUT OMITTED]...
etc/origin/cloudprovider/openstack.conf
etc/origin/node/system:node:master-0.example.com.crt
etc/origin/node/system:node:master-0.example.com.key
etc/origin/node/ca.crt
etc/origin/node/system:node:master-0.example.com.kubeconfig
etc/origin/node/server.crt
etc/origin/node/server.key
etc/origin/node/node-dnsmasq.conf
etc/origin/node/resolv.conf
etc/origin/node/node-config.yaml
etc/origin/node/flannel.etcd-client.key
etc/origin/node/flannel.etcd-client.csr
etc/origin/node/flannel.etcd-client.crt
etc/origin/node/flannel.etcd-ca.crt
etc/pki/ca-trust/source/anchors/openshift-ca.crt
etc/pki/ca-trust/source/anchors/registry-ca.crt
etc/dnsmasq.conf
etc/dnsmasq.d/origin-dns.conf
etc/dnsmasq.d/origin-upstream-dns.conf
etc/dnsmasq.d/node-dnsmasq.conf
packages.txt

If needed, you can compress the files to save space:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo tar -zcvf /backup/$(hostname)-$(date +%Y%m%d).tar.gz $MYBACKUPDIR
$ sudo rm -Rf ${MYBACKUPDIR}

The openshift-ansible-contrib script is not supported by Red Hat, but the reference architecture team performs testing to ensure the code operates as defined and is secure.

You can run the script on every master host with:

$ mkdir ~/git
$ cd ~/git
$ git clone https://github.com/openshift/openshift-ansible-contrib.git
$ cd openshift-ansible-contrib/reference-architecture/day2ops/scripts
$ ./backup_master_node.sh -h

Restoring a master host backup

After creating a backup of important master host files, if they become corrupted or accidentally removed, you can restore the files by copying the files back to master, ensuring they contain the proper content, and restarting the affected services.

Procedure

Restore the /etc/origin/master/master-config.yaml file:

# MYBACKUPDIR=*/backup/$(hostname)/$(date +%Y%m%d)*
# cp /etc/origin/master/master-config.yaml /etc/origin/master/master-config.yaml.old
# cp /backup/$(hostname)/$(date +%Y%m%d)/origin/master/master-config.yaml /etc/origin/master/master-config.yaml
# systemctl restart atomic-openshift-master-api
# systemctl restart atomic-openshift-master-controllers

Restarting the master services can lead to downtime. However, you can remove the master host from the highly available load balancer pool, then perform the restore operation. Once the service has been properly restored, you can add the master host back to the load balancer pool.

Perform a full reboot of the affected instance to restore the iptables configuration.

If you cannot restart OpenShift Container Platform because packages are missing, reinstall the packages.
1. Get the list of the current installed packages:
  $ rpm -qa | sort > /tmp/current_packages.txt
2. View the differences between the package lists:
  $ diff /tmp/current_packages.txt ${MYBACKUPDIR}/packages.txt > ansible-2.4.0.0-5.el7.noarch
3. Reinstall the missing packages:
  # yum reinstall -y <packages> (1)
  1 Replace <packages> with the packages that are different between the package lists.
Restore a system certificate by copying the certificate to the /etc/pki/ca-trust/source/anchors/ directory and execute the update-ca-trust:
```
$ MYBACKUPDIR=*/backup/$(hostname)/$(date +%Y%m%d)*
$ sudo cp ${MYBACKUPDIR}/external_certificates/my_company.crt /etc/pki/ca-trust/source/anchors/
$ sudo update-ca-trust
```
Always ensure the user ID and group ID are restored when the files are copied back, as well as the SELinux context.

Node host tasks

Deprecating a node host

The procedure is the same whether deprecating an infrastructure node or an application node.

Prerequisites

Ensure enough capacity is available to migrate the existing pods from the node set to be removed. Removing an infrastructure node is advised only when at least two more nodes will stay online after the infrastructure node is removed.

Procedure

List all available nodes to find the node to deprecate:

$ oc get nodes
NAME                  STATUS                     AGE       VERSION
ocp-infra-node-b7pl   Ready                      23h       v1.6.1+5115d708d7
ocp-infra-node-p5zj   Ready                      23h       v1.6.1+5115d708d7
ocp-infra-node-rghb   Ready                      23h       v1.6.1+5115d708d7
ocp-master-dgf8       Ready,SchedulingDisabled   23h       v1.6.1+5115d708d7
ocp-master-q1v2       Ready,SchedulingDisabled   23h       v1.6.1+5115d708d7
ocp-master-vq70       Ready,SchedulingDisabled   23h       v1.6.1+5115d708d7
ocp-node-020m         Ready                      23h       v1.6.1+5115d708d7
ocp-node-7t5p         Ready                      23h       v1.6.1+5115d708d7
ocp-node-n0dd         Ready                      23h       v1.6.1+5115d708d7

As an example, this topic deprecates the ocp-infra-node-b7pl infrastructure node.

Describe the node and its running services:

$ oc describe node ocp-infra-node-b7pl
Name:			ocp-infra-node-b7pl
Role:
Labels:			beta.kubernetes.io/arch=amd64
			beta.kubernetes.io/instance-type=n1-standard-2
			beta.kubernetes.io/os=linux
			failure-domain.beta.kubernetes.io/region=europe-west3
			failure-domain.beta.kubernetes.io/zone=europe-west3-c
			kubernetes.io/hostname=ocp-infra-node-b7pl
			role=infra
Annotations:		volumes.kubernetes.io/controller-managed-attach-detach=true
Taints:			<none>
CreationTimestamp:	Wed, 22 Nov 2017 09:36:36 -0500
Phase:
Conditions:
  ...
Addresses:		10.156.0.11,ocp-infra-node-b7pl
Capacity:
 cpu:		2
 memory:	7494480Ki
 pods:		20
Allocatable:
 cpu:		2
 memory:	7392080Ki
 pods:		20
System Info:
 Machine ID:			bc95ccf67d047f2ae42c67862c202e44
 System UUID:			9762CC3D-E23C-AB13-B8C5-FA16F0BCCE4C
 Boot ID:			ca8bf088-905d-4ec0-beec-8f89f4527ce4
 Kernel Version:		3.10.0-693.5.2.el7.x86_64
 OS Image:			Employee SKU
 Operating System:		linux
 Architecture:			amd64
 Container Runtime Version:	docker://1.12.6
 Kubelet Version:		v1.6.1+5115d708d7
 Kube-Proxy Version:		v1.6.1+5115d708d7
ExternalID:			437740049672994824
Non-terminated Pods:		(2 in total)
  Namespace			Name				CPU Requests	CPU Limits	Memory Requests	Memory Limits
  ---------			----				------------	----------	---------------	-------------
  default			docker-registry-1-5szjs		100m (5%)	0 (0%)		256Mi (3%)0 (0%)
  default			router-1-vzlzq			100m (5%)	0 (0%)		256Mi (3%)0 (0%)
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  CPU Requests	CPU Limits	Memory Requests	Memory Limits
  ------------	----------	---------------	-------------
  200m (10%)	0 (0%)		512Mi (7%)	0 (0%)
Events:		<none>

The output above shows that the node is running two pods: router-1-vzlzq and docker-registry-1-5szjs. Two more infrastructure nodes are available to migrate these two pods.

The cluster described above is a highly available cluster, this means both the router and docker-registry services are running on all infrastructure nodes.

Mark a node as unschedulable and evacuate all of its pods:

$ oc adm drain ocp-infra-node-b7pl --delete-local-data
node "ocp-infra-node-b7pl" cordoned
WARNING: Deleting pods with local storage: docker-registry-1-5szjs
pod "docker-registry-1-5szjs" evicted
pod "router-1-vzlzq" evicted
node "ocp-infra-node-b7pl" drained

If the pod has attached local storage (for example, EmptyDir), the --delete-local-data option must be provided. Generally, pods running in production should use the local storage only for temporary or cache files, but not for anything important or persistent. For regular storage, applications should use object storage or persistent volumes. In this case, the docker-registry pod’s local storage is empty, because the object storage is used instead to store the container images.

The above operation deletes existing pods running on the node. Then, new pods are created according to the replication controller.

In general, every application should be deployed with a deployment configuration, which creates pods using the replication controller.

oc adm drain will not delete any bare pods (pods that are neither mirror pods nor managed by ReplicationController, ReplicaSet, DaemonSet, StatefulSet, or a job). To do so, the --force option is required. Be aware that the bare pods will not be recreated on other nodes and data may be lost during this operation.

The example below shows the output of the replication controller of the registry:

$ oc describe rc/docker-registry-1
Name:		docker-registry-1
Namespace:	default
Selector:	deployment=docker-registry-1,deploymentconfig=docker-registry,docker-registry=default
Labels:		docker-registry=default
		openshift.io/deployment-config.name=docker-registry
Annotations: ...
Replicas:	3 current / 3 desired
Pods Status:	3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:		deployment=docker-registry-1
			deploymentconfig=docker-registry
			docker-registry=default
  Annotations:		openshift.io/deployment-config.latest-version=1
			openshift.io/deployment-config.name=docker-registry
			openshift.io/deployment.name=docker-registry-1
  Service Account:	registry
  Containers:
   registry:
    Image:	openshift3/ose-docker-registry:v3.6.173.0.49
    Port:	5000/TCP
    Requests:
      cpu:	100m
      memory:	256Mi
    Liveness:	http-get https://:5000/healthz delay=10s timeout=5s period=10s #success=1 #failure=3
    Readiness:	http-get https://:5000/healthz delay=0s timeout=5s period=10s #success=1 #failure=3
    Environment:
      REGISTRY_HTTP_ADDR:					:5000
      REGISTRY_HTTP_NET:					tcp
      REGISTRY_HTTP_SECRET:					tyGEnDZmc8dQfioP3WkNd5z+Xbdfy/JVXf/NLo3s/zE=
      REGISTRY_MIDDLEWARE_REPOSITORY_OPENSHIFT_ENFORCEQUOTA:	false
      REGISTRY_HTTP_TLS_KEY:					/etc/secrets/registry.key
      OPENSHIFT_DEFAULT_REGISTRY:				docker-registry.default.svc:5000
      REGISTRY_CONFIGURATION_PATH:				/etc/registry/config.yml
      REGISTRY_HTTP_TLS_CERTIFICATE:				/etc/secrets/registry.crt
    Mounts:
      /etc/registry from docker-config (rw)
      /etc/secrets from registry-certificates (rw)
      /registry from registry-storage (rw)
  Volumes:
   registry-storage:
    Type:	EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:
   registry-certificates:
    Type:	Secret (a volume populated by a Secret)
    SecretName:	registry-certificates
    Optional:	false
   docker-config:
    Type:	Secret (a volume populated by a Secret)
    SecretName:	registry-config
    Optional:	false
Events:
  FirstSeen	LastSeen	Count	From			SubObjectPath	Type		Reason		Message
  ---------	--------	-----	----			-------------	--------	------		-------
  49m		49m		1	replication-controller			Normal		SuccessfulCreate	Created pod: docker-registry-1-dprp5

The event at the bottom of the output displays information about new pod creation. So, when listing all pods:

$ oc get pods
NAME                       READY     STATUS    RESTARTS   AGE
docker-registry-1-dprp5    1/1       Running   0          52m
docker-registry-1-kr8jq    1/1       Running   0          1d
docker-registry-1-ncpl2    1/1       Running   0          1d
registry-console-1-g4nqg   1/1       Running   0          1d
router-1-2gshr             0/1       Pending   0          52m
router-1-85qm4             1/1       Running   0          1d
router-1-q5sr8             1/1       Running   0          1d

The docker-registry-1-5szjs and router-1-vzlzq pods that were running on the now deprecated node are no longer available. Instead, two new pods have been created: docker-registry-1-dprp5 and router-1-2gshr. As shown above, the new router pod is router-1-2gshr, but is in the Pending state. This is because every node can be running only on one single router and is bound to the ports 80 and 443 of the host.
When observing the newly created registry pod, the example below shows that the pod has been created on the ocp-infra-node-rghb node, which is different from the deprecating node:
```
$ oc describe pod docker-registry-1-dprp5
Name:			docker-registry-1-dprp5
Namespace:		default
Security Policy:	hostnetwork
Node:			ocp-infra-node-rghb/10.156.0.10
...
```
The only difference between deprecating the infrastructure and the application node is that once the infrastructure node is evacuated, and if there is no plan to replace that node, the services running on infrastructure nodes can be scaled down:
```
$ oc scale dc/router --replicas 2
deploymentconfig "router" scaled

$ oc scale dc/docker-registry --replicas 2
deploymentconfig "docker-registry" scaled
```

Now, every infrastructure node is running only one kind of each pod:

$ oc get pods
NAME                       READY     STATUS    RESTARTS   AGE
docker-registry-1-kr8jq    1/1       Running   0          1d
docker-registry-1-ncpl2    1/1       Running   0          1d
registry-console-1-g4nqg   1/1       Running   0          1d
router-1-85qm4             1/1       Running   0          1d
router-1-q5sr8             1/1       Running   0          1d

$ oc describe po/docker-registry-1-kr8jq | grep Node:
Node:			ocp-infra-node-p5zj/10.156.0.9

$ oc describe po/docker-registry-1-ncpl2 | grep Node:
Node:			ocp-infra-node-rghb/10.156.0.10

To provide a full highly available cluster, at least three infrastructure nodes should always be available.

To verify that the scheduling on the node is disabled:

$ oc get nodes
NAME                  STATUS                     AGE       VERSION
ocp-infra-node-b7pl   Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-infra-node-p5zj   Ready                      1d        v1.6.1+5115d708d7
ocp-infra-node-rghb   Ready                      1d        v1.6.1+5115d708d7
ocp-master-dgf8       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-master-q1v2       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-master-vq70       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-node-020m         Ready                      1d        v1.6.1+5115d708d7
ocp-node-7t5p         Ready                      1d        v1.6.1+5115d708d7
ocp-node-n0dd         Ready                      1d        v1.6.1+5115d708d7

And that the node does not contain any pods:

$ oc describe node ocp-infra-node-b7pl
Name:			ocp-infra-node-b7pl
Role:
Labels:			beta.kubernetes.io/arch=amd64
			beta.kubernetes.io/instance-type=n1-standard-2
			beta.kubernetes.io/os=linux
			failure-domain.beta.kubernetes.io/region=europe-west3
			failure-domain.beta.kubernetes.io/zone=europe-west3-c
			kubernetes.io/hostname=ocp-infra-node-b7pl
			role=infra
Annotations:		volumes.kubernetes.io/controller-managed-attach-detach=true
Taints:			<none>
CreationTimestamp:	Wed, 22 Nov 2017 09:36:36 -0500
Phase:
Conditions:
  ...
Addresses:		10.156.0.11,ocp-infra-node-b7pl
Capacity:
 cpu:		2
 memory:	7494480Ki
 pods:		20
Allocatable:
 cpu:		2
 memory:	7392080Ki
 pods:		20
System Info:
 Machine ID:			bc95ccf67d047f2ae42c67862c202e44
 System UUID:			9762CC3D-E23C-AB13-B8C5-FA16F0BCCE4C
 Boot ID:			ca8bf088-905d-4ec0-beec-8f89f4527ce4
 Kernel Version:		3.10.0-693.5.2.el7.x86_64
 OS Image:			Employee SKU
 Operating System:		linux
 Architecture:			amd64
 Container Runtime Version:	docker://1.12.6
 Kubelet Version:		v1.6.1+5115d708d7
 Kube-Proxy Version:		v1.6.1+5115d708d7
ExternalID:			437740049672994824
Non-terminated Pods:		(0 in total)
  Namespace			Name		CPU Requests	CPU Limits	Memory Requests	Memory Limits
  ---------			----		------------	----------	---------------	-------------
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  CPU Requests	CPU Limits	Memory Requests	Memory Limits
  ------------	----------	---------------	-------------
  0 (0%)	0 (0%)		0 (0%)		0 (0%)
Events:		<none>

Remove the infrastructure instance from the backend section in the /etc/haproxy/haproxy.cfg configuration file:

backend router80
    balance source
    mode tcp
    server infra-1.example.com 192.168.55.12:80 check
    server infra-2.example.com 192.168.55.13:80 check

backend router443
    balance source
    mode tcp
    server infra-1.example.com 192.168.55.12:443 check
    server infra-2.example.com 192.168.55.13:443 check

Then, restart the haproxy service.
```
$ sudo systemctl restart haproxy
```

Remove the node from the cluster after all pods are evicted with command:

$ oc delete node ocp-infra-node-b7pl
node "ocp-infra-node-b7pl" deleted

$ oc get nodes
NAME                  STATUS                     AGE       VERSION
ocp-infra-node-p5zj   Ready                      1d        v1.6.1+5115d708d7
ocp-infra-node-rghb   Ready                      1d        v1.6.1+5115d708d7
ocp-master-dgf8       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-master-q1v2       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-master-vq70       Ready,SchedulingDisabled   1d        v1.6.1+5115d708d7
ocp-node-020m         Ready                      1d        v1.6.1+5115d708d7
ocp-node-7t5p         Ready                      1d        v1.6.1+5115d708d7
ocp-node-n0dd         Ready                      1d        v1.6.1+5115d708d7

For more information on evacuating and draining pods or nodes, see Node maintenance section.

Replacing a node host

In the event that a node would need to be added in place of the deprecated node, follow the Adding hosts to an existing cluster section.

Creating a node host backup

Creating a backup of a node host is a different use case from backing up a master host. Because master hosts contain many important files, creating a backup is highly recommended. However, the nature of nodes is that anything special is replicated over the nodes in case of failover, and they typically do not contain data that is necessary to run an environment. If a backup of a node contains something necessary to run an environment, then a creating a backup is recommended.

The backup process is to be performed before any change to the infrastructure, such as a system update, upgrade, or any other significant modification. Backups should be performed on a regular basis to ensure the most recent data is available if a failure occurs.

OpenShift Container Platform files

Node instances run applications in the form of pods, which are based on containers. The /etc/origin/ and /etc/origin/node directories house important files, such as:

The configuration of the node services
Certificates generated by the installation
Cloud provider-related configuration
Keys and other authentication files, such as the dnsmasq configuration

The OpenShift Container Platform services can be customized to increase the log level, use proxies, and more, and the configuration files are stored in the /etc/sysconfig directory.

Procedure

Create a backup of the node configuration files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo cp -aR /etc/origin ${MYBACKUPDIR}/etc
$ sudo cp -aR /etc/sysconfig/atomic-openshift-node ${MYBACKUPDIR}/etc/sysconfig/

OpenShift Container Platform uses specific files that must be taken into account when planning the backup policy, including:

File

Description

/etc/cni/*

Container Network Interface configuration (if used)

/etc/sysconfig/iptables

Where the iptables rules are stored

/etc/sysconfig/docker-storage-setup

The input file for container-storage-setup command

/etc/sysconfig/docker

The docker configuration file

/etc/sysconfig/docker-network

docker networking configuration (i.e. MTU)

/etc/sysconfig/docker-storage

docker storage configuration (generated by container-storage-setup)

/etc/dnsmasq.conf

Main configuration file for dnsmasq

/etc/dnsmasq.d/*

Different dnsmasq configuration files

/etc/sysconfig/flanneld

flannel configuration file (if used)

/etc/pki/ca-trust/source/anchors/

Certificates added to the system (i.e. for external registries)

To create those files:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}/etc/sysconfig
$ sudo mkdir -p ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors
$ sudo cp -aR /etc/sysconfig/{iptables,docker-*,flanneld} \
    ${MYBACKUPDIR}/etc/sysconfig/
$ sudo cp -aR /etc/dnsmasq* /etc/cni ${MYBACKUPDIR}/etc/
$ sudo cp -aR /etc/pki/ca-trust/source/anchors/* \
    ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors/

If a package is accidentally removed, or a file included in an rpm package should be restored, having a list of rhel packages installed on the system can be useful.

If using Red Hat Satellite features, such as content views or the facts store, provide a proper mechanism to reinstall the missing packages and a historical data of packages installed in the systems.

To create a list of the current rhel packages installed in the system:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo mkdir -p ${MYBACKUPDIR}
$ rpm -qa | sort | sudo tee $MYBACKUPDIR/packages.txt

The following files should now be present in the backup directory:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo find ${MYBACKUPDIR} -mindepth 1 -type f -printf '%P\n'
etc/sysconfig/atomic-openshift-node
etc/sysconfig/flanneld
etc/sysconfig/iptables
etc/sysconfig/docker-network
etc/sysconfig/docker-storage
etc/sysconfig/docker-storage-setup
etc/sysconfig/docker-storage-setup.rpmnew
etc/origin/node/system:node:app-node-0.example.com.crt
etc/origin/node/system:node:app-node-0.example.com.key
etc/origin/node/ca.crt
etc/origin/node/system:node:app-node-0.example.com.kubeconfig
etc/origin/node/server.crt
etc/origin/node/server.key
etc/origin/node/node-dnsmasq.conf
etc/origin/node/resolv.conf
etc/origin/node/node-config.yaml
etc/origin/node/flannel.etcd-client.key
etc/origin/node/flannel.etcd-client.csr
etc/origin/node/flannel.etcd-client.crt
etc/origin/node/flannel.etcd-ca.crt
etc/origin/cloudprovider/openstack.conf
etc/pki/ca-trust/source/anchors/openshift-ca.crt
etc/pki/ca-trust/source/anchors/registry-ca.crt
etc/dnsmasq.conf
etc/dnsmasq.d/origin-dns.conf
etc/dnsmasq.d/origin-upstream-dns.conf
etc/dnsmasq.d/node-dnsmasq.conf
packages.txt

If needed, the files can be compressed to save space:

$ MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
$ sudo tar -zcvf /backup/$(hostname)-$(date +%Y%m%d).tar.gz $MYBACKUPDIR
$ sudo rm -Rf ${MYBACKUPDIR}

To create any of these files from scratch, the openshift-ansible-contrib repository contains the backup_master_node.sh script, which performs the previous steps. The script creates a directory on the host running the script and copies all the files previously mentioned.

The openshift-ansible-contrib script is not supported by Red Hat, but the reference architecture team performs testing to ensure the code operates as defined and is secure.

The script can be executed on every master host with:

$ mkdir ~/git
$ cd ~/git
$ git clone https://github.com/openshift/openshift-ansible-contrib.git
$ cd openshift-ansible-contrib/reference-architecture/day2ops/scripts
$ ./backup_master_node.sh -h

Restoring a node host backup

After creating a backup of important node host files, if they become corrupted or accidentally removed, you can restore the file by copying back the file, ensuring it contains the proper content and restart the affected services.

Procedure

Restore the /etc/origin/node/node-config.yaml file:

# MYBACKUPDIR=/backup/$(hostname)/$(date +%Y%m%d)
# cp /etc/origin/node/node-config.yaml /etc/origin/node/node-config.yaml.old
# cp /backup/$(hostname)/$(date +%Y%m%d)/etc/origin/node/node-config.yaml /etc/origin/node/node-config.yaml
# systemctl restart atomic-openshift-node

Restarting the services can lead to downtime. See Node maintenance, for tips on how to ease the process.

Perform a full reboot of the affected instance to restore the iptables configuration.

If you cannot restart OpenShift Container Platform because packages are missing, reinstall the packages.
1. Get the list of the current installed packages:
  $ rpm -qa | sort > /tmp/current_packages.txt
2. View the differences between the package lists:
  $ diff /tmp/current_packages.txt ${MYBACKUPDIR}/packages.txt > ansible-2.4.0.0-5.el7.noarch
3. Reinstall the missing packages:
  # yum reinstall -y <packages> (1)
  1 Replace <packages> with the packages that are different between the package lists.
Restore a system certificate by copying the certificate to the /etc/pki/ca-trust/source/anchors/ directory and execute the update-ca-trust:
```
$ MYBACKUPDIR=*/backup/$(hostname)/$(date +%Y%m%d)*
$ sudo cp ${MYBACKUPDIR}/etc/pki/ca-trust/source/anchors/my_company.crt /etc/pki/ca-trust/source/anchors/
$ sudo update-ca-trust
```
Always ensure proper user ID and group ID are restored when the files are copied back, as well as the SELinux context.

Node maintenance and next steps

See Managing nodes or Managing pods topics for various node management options. These include:

A node can reserve a portion of its resources to be used by specific components. These include the kubelet, kube-proxy, Docker, or other remaining system components such as sshd and NetworkManager. See the Allocating node resources section in the Cluster Administrator guide for more information.

etcd tasks

etcd backup

etcd is the key value store for all object definitions, as well as the persistent master state. Other components watch for changes, then bring themselves into the desired state.

OpenShift Container Platform versions prior to 3.5 use etcd version 2 (v2), while 3.5 and later use version 3 (v3). The data model between the two versions of etcd is different. etcd v3 can use both the v2 and v3 data models, whereas etcd v2 can only use the v2 data model. In an etcd v3 server, the v2 and v3 data stores exist in parallel and are independent.

For both v2 and v3 operations, you can use the ETCDCTL_API environment variable to use the proper API:

$ etcdctl -v
etcdctl version: 3.2.5
API version: 2
$ ETCDCTL_API=3 etcdctl version
etcdctl version: 3.2.5
API version: 3.2

See Migrating etcd Data (v2 to v3) section for information about how to migrate to v3.

The etcd backup process is composed of two different procedures:

Configuration backup: Including the required etcd configuration and certificates
Data backup: Including both v2 and v3 data model.

You can perform the data backup process on any host that has connectivity to the etcd cluster, where the proper certificates are provided, and where the etcdctl tool is installed.

The backup files must be copied to an external system, ideally outside the OpenShift Container Platform environment, and then encrypted.

Note that the etcd backup still has all the references to current storage volumes. When you restore etcd, OpenShift Container Platform starts launching the previous pods on nodes and reattaching the same storage. This process is no different than the process of when you remove a node from the cluster and add a new one back in its place. Anything attached to that node is reattached to the pods on whatever nodes they are rescheduled to.

Backing up etcd

When you back up etcd, you must back up both the etcd configuration files and the etcd data.

Backing up etcd configuration files

Procedure

For each etcd member of the cluster, back up the etcd configuration.

$ ssh master-0
# mkdir -p /backup/etcd-config-$(date +%Y%m%d)/
# cp -R /etc/etcd/ /backup/etcd-config-$(date +%Y%m%d)/

The certificates and configuration files on each etcd cluster member are unique.

Backing up etcd data

Prerequisites

The OpenShift Container Platform installer creates aliases to avoid typing all the flags named etcdctl2 for etcd v2 tasks and etcdctl3 for etcd v3 tasks.

However, the etcdctl3 alias does not provide the full endpoint list to the etcdctl command, so the --endpoints option with all the endpoints must be provided.

Before backing up etcd:

etcdctl binaries should be available or, in containerized installations, the rhel7/etcd container should be available
Ensure connectivity with the etcd cluster (port 2379/tcp)
Ensure the proper certificates to connect to the etcd cluster

Procedure

Back up the etcd data:

If you use the v2 API, take the following actions:

Stop all etcd services:
```
# systemctl stop etcd.service
```

Create the etcd data backup and copy the etcd db file:

# mkdir -p /backup/etcd-$(date +%Y%m%d)
# etcdctl2 backup \
    --data-dir /var/lib/etcd \
    --backup-dir /backup/etcd-$(date +%Y%m%d)
# cp /var/lib/etcd/member/snap/db /backup/etcd-$(date +%Y%m%d)

Start all etcd services:
```
# systemctl start etcd.service
```

If you use the v3 API, run the following commands:

Because clusters upgraded from previous versions of OpenShift Container Platform might contain v2 data stores, back up both v2 and v3 datastores.
1. Back up etcd v3 data:
  # systemctl show etcd --property=ActiveState,SubState # mkdir -p /backup/etcd-$(date +%Y%m%d) # etcdctl3 snapshot save */backup/etcd-$(date +%Y%m%d)*/db Snapshot saved at /backup/etcd-<date>/db
2. Back up etcd v2 data:
  # systemctl stop etcd.service # etcdctl2 backup \ --data-dir /var/lib/etcd \ --backup-dir /backup/etcd-$(date +%Y%m%d) # cp /var/lib/etcd/member/snap/db /backup/etcd-$(date +%Y%m%d) # systemctl start etcd.service
  The etcdctl snapshot save command requires the etcd service to be running.
  
  In these commands, a /backup/etcd-<date>/ directory is created, where <date> represents the current date, which must be an external NFS share, S3 bucket, or any external storage location.
  
  In the case of an all-in-one cluster, the etcd data directory is located in the /var/lib/origin/openshift.local.etcd directory.

Restoring etcd

The restore procedure for etcd configuration files replaces the appropriate files, then restarts the service.

If an etcd host has become corrupted and the /etc/etcd/etcd.conf file is lost, restore it using:

$ ssh master-0
# cp /backup/yesterday/master-0-files/etcd.conf /etc/etcd/etcd.conf
# restorecon -Rv /etc/etcd/etcd.conf
# systemctl restart etcd.service

In this example, the backup file is stored in the /backup/yesterday/master-0-files/etcd.conf path where it can be used as an external NFS share, S3 bucket, or other storage solution.

Restoring etcd v2 & v3 data

The following process restores healthy data files and starts the etcd cluster as a single node, then adds the rest of the nodes if an etcd cluster is required.

Procedure

Stop all etcd services:
```
# systemctl stop etcd.service
```
To ensure the proper backup is restored, delete the etcd directories:
- To back up the current etcd data before you delete the directory, run the following command:
  # mv /var/lib/etcd /var/lib/etcd.old # mkdir /var/lib/etcd # chown -R etcd.etcd /var/lib/etcd/ # restorecon -Rv /var/lib/etcd/
- Or, to delete the directory and the etcd, data, run the following command:
  # rm -Rf /var/lib/etcd/*
  In an all-in-one cluster, the etcd data directory is located in the /var/lib/origin/openshift.local.etcd directory.

Restore a healthy backup data file to each of the etcd nodes. Perform this step on all etcd hosts, including master hosts collocated with etcd.

# cp -R /backup/etcd-xxx/* /var/lib/etcd/
# mv /var/lib/etcd/db /var/lib/etcd/member/snap/db
# chcon -R --reference /backup/etcd-xxx/* /var/lib/etcd/
# chown -R etcd:etcd /var/lib/etcd/R

Run the etcd service on each host, forcing a new cluster.

This creates a custom file for the etcd service, which overwrites the execution command adding the --force-new-cluster option:

# mkdir -p /etc/systemd/system/etcd.service.d/
# echo "[Service]" > /etc/systemd/system/etcd.service.d/temp.conf
# echo "ExecStart=" >> /etc/systemd/system/etcd.service.d/temp.conf
# sed -n '/ExecStart/s/"$/ --force-new-cluster"/p' \
    /usr/lib/systemd/system/etcd.service \
    >> /etc/systemd/system/etcd.service.d/temp.conf

# systemctl daemon-reload
# systemctl restart etcd

Check for error messages:
```
$ journalctl -fu etcd.service
```

Check for health status:

# etcdctl2 cluster-health
member 5ee217d17301 is healthy: got healthy result from https://192.168.55.8:2379
cluster is healthy

Restart the etcd service in cluster mode:

# rm -f /etc/systemd/system/etcd.service.d/temp.conf
# systemctl daemon-reload
# systemctl restart etcd

Check for health status and member list:

# etcdctl2 cluster-health
member 5ee217d17301 is healthy: got healthy result from https://192.168.55.8:2379
cluster is healthy

# etcdctl2 member list
5ee217d17301: name=master-0.example.com peerURLs=http://localhost:2380 clientURLs=https://192.168.55.8:2379 isLeader=true

After the first instance is running, you can restore the rest of your etcd servers.

Fix the `peerURLS` parameter

After restoring the data and creating a new cluster, the peerURLs parameter shows localhost instead of the IP where etcd is listening for peer communication:

# etcdctl2 member list
5ee217d17301: name=master-0.example.com peerURLs=http://*localhost*:2380 clientURLs=https://192.168.55.8:2379 isLeader=true

Procedure

Get the member ID using etcdctl member list:
```
`etcdctl member list`
```
Get the IP where etcd listens for peer communication:
```
$ ss -l4n | grep 2380
```

Update the member information with that IP:

# etcdctl2 member update 5ee217d17301 https://192.168.55.8:2380
Updated member with ID 5ee217d17301 in cluster

To verify, check that the IP is in the member list:

$ etcdctl2 member list
5ee217d17301: name=master-0.example.com peerURLs=https://*192.168.55.8*:2380 clientURLs=https://192.168.55.8:2379 isLeader=true

Restoring etcd for v3

The restore procedure for v3 data is similar to the restore procedure for the v2 data.

Snapshot integrity may be optionally verified at restore time. If the snapshot is taken with etcdctl snapshot save, it will have an integrity hash that is checked by etcdctl snapshot restore. If the snapshot is copied from the data directory, there is no integrity hash and it will only restore by using --skip-hash-check.

The procedure to restore only the v3 data must be performed on a single etcd host. You can then add the rest of the nodes to the cluster.

Procedure

Stop all etcd services:
```
# systemctl stop etcd.service
```
Clear all old data, because etcdctl recreates it in the node where the restore procedure is going to be performed:
```
# rm -Rf /var/lib/etcd
```

Run the snapshot restore command, substituting the values from the /etc/etcd/etcd.conf file:

# etcdctl3 snapshot restore /backup/etcd-xxxxxx/backup.db \
  --data-dir /var/lib/etcd \
  --name master-0.example.com \
  --initial-cluster "master-0.example.com=https://192.168.55.8:2380" \ --initial-cluster-token "etcd-cluster-1" \
  --initial-advertise-peer-urls https://192.168.55.8:2380

2017-10-03 08:55:32.440779 I | mvcc: restore compact to 1041269
2017-10-03 08:55:32.468244 I | etcdserver/membership: added member 40bef1f6c79b3163 [https://192.168.55.8:2380] to cluster 26841ebcf610583c

Restore permissions and selinux context to the restored files:

# chown -R etcd.etcd /var/lib/etcd/
# restorecon -Rv /var/lib/etcd

Start the etcd service:
```
# systemctl start etcd
```
Check for any error messages:
```
$ journalctl -fu etcd.service
```

Replacing an etcd host

To replace an etcd host, scale up the etcd cluster and then remove the host. This process ensures that you keep quorum if you lose an etcd host during the replacement procedure.

The etcd cluster must maintain a quorum during the replacement operation. This means that at least one host must be in operation at all times.

If the host replacement operation occurs while the etcd cluster maintains a quorum, cluster operations are usually not affected. If a large amount of etcd data must replicate, some operations might slow down.

Before you start any procedure involving the etcd cluster, you must have a backup of the etcd data and configuration files so that you can restore the cluster if the procedure fails.

Scaling etcd

You can scale the etcd cluster vertically by adding more resources to the etcd hosts or horizontally by adding more etcd hosts.

Due to the voting system etcd uses, the cluster must always contain an odd number of members.

Having a cluster with an odd number of etcd hosts can account for fault tolerance. Having an odd number of etcd hosts does not change the number needed for a quorum but increases the tolerance for failure. For example, with a cluster of three members, quorum is two, which leaves a failure tolerance of one. This ensures the cluster continues to operate if two of the members are healthy.

Having an in-production cluster of three etcd hosts is recommended.

The new host requires a fresh Red Hat Enterprise Linux version 7 dedicated host. The etcd storage should be located on an SSD disk to achieve maximum performance and on a dedicated disk mounted in /var/lib/etcd.

Prerequisites

Before you add a new etcd host, perform a backup of both etcd configuration and data to prevent data loss.

Check the current etcd cluster status to avoid adding new hosts to an unhealthy cluster.

If you use the v2 etcd api, run this command:

# etcdctl --cert-file=/etc/etcd/peer.crt \
          --key-file=/etc/etcd/peer.key \
          --ca-file=/etc/etcd/ca.crt \
          --peers="https://*master-0.example.com*:2379,\
          https://*master-1.example.com*:2379,\
          https://*master-2.example.com*:2379"\
          cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

If you use the v3 etcd api, run this command:

# ETCDCTL_API=3 etcdctl --cert="/etc/etcd/peer.crt" \
          --key=/etc/etcd/peer.key \
          --cacert="/etc/etcd/ca.crt" \
          --endpoints="https://*master-0.example.com*:2379,\
            https://*master-1.example.com*:2379,\
            https://*master-2.example.com*:2379"
            endpoint health
https://master-0.example.com:2379 is healthy: successfully committed proposal: took = 5.011358ms
https://master-1.example.com:2379 is healthy: successfully committed proposal: took = 1.305173ms
https://master-2.example.com:2379 is healthy: successfully committed proposal: took = 1.388772ms

Before running the scaleup playbook, ensure the new host is registered to the proper Red Hat software channels:

# subscription-manager register \
    --username=*<username>* --password=*<password>*
# subscription-manager attach --pool=*<poolid>*
# subscription-manager repos --disable="*"
# subscription-manager repos \
    --enable=rhel-7-server-rpms \
    --enable=rhel-7-server-extras-rpms

etcd is hosted in the rhel-7-server-extras-rpms software channel.

Upgrade etcd and iptables on the current etcd nodes:
```
# yum update etcd iptables-services
```
Back up the /etc/etcd configuration for the etcd hosts.
If the new etcd members will also be OpenShift Container Platform nodes, add the desired number of hosts to the cluster.
The rest of this procedure assumes you added one host, but if you add multiple hosts, perform all steps on each host.

Adding a new etcd host using Ansible

Procedure

In the Ansible inventory file, create a new group named [new_etcd] and add the new host. Then, add the new_etcd group as a child of the [OSEv3] group:

[OSEv3:children]
masters
nodes
etcd
new_etcd (1)

... [OUTPUT ABBREVIATED] ...

[etcd]
master-0.example.com
master-1.example.com
master-2.example.com

[new_etcd] (1)
etcd0.example.com (1)

1	Add these lines.

From the host that installed OpenShift Container Platform and hosts the Ansible inventory file, run the etcd scaleup playbook:
```
$ ansible-playbook  /usr/share/ansible/openshift-ansible/playbooks/byo/openshift-etcd/scaleup.yml
```

After the playbook runs, modify the inventory file to reflect the current status by moving the new etcd host from the [new_etcd] group to the [etcd] group:

[OSEv3:children]
masters
nodes
etcd
new_etcd

... [OUTPUT ABBREVIATED] ...

[etcd]
master-0.example.com
master-1.example.com
master-2.example.com
etcd0.example.com

If you use Flannel, modify the flanneld service configuration on every OpenShift Container Platform host, located at /etc/sysconfig/flanneld, to include the new etcd host:
```
FLANNEL_ETCD_ENDPOINTS=https://master-0.example.com:2379,https://master-1.example.com:2379,https://master-2.example.com:2379,https://etcd0.example.com:2379
```
Restart the flanneld service:
```
# systemctl restart flanneld.service
```

Manually adding a new etcd host

Procedure

Modify the current etcd cluster

To create the etcd certificates, run the openssl command, replacing the values with those from your environment.

Create some environment variables:

export NEW_ETCD_HOSTNAME="*etcd0.example.com*"
export NEW_ETCD_IP="192.168.55.21"

export CN=$NEW_ETCD_HOSTNAME
export SAN="IP:${NEW_ETCD_IP}, DNS:${NEW_ETCD_HOSTNAME}"
export PREFIX="/etc/etcd/generated_certs/etcd-$CN/"
export OPENSSLCFG="/etc/etcd/ca/openssl.cnf"

The custom openssl extensions used as etcd_v3_ca_* include the $SAN environment variable as subjectAltName. See /etc/etcd/ca/openssl.cnf for more information.

Create the directory to store the configuration and certificates:
```
# mkdir -p ${PREFIX}
```

Create the server certificate request and sign it: (server.csr and server.crt)

# openssl req -new -config ${OPENSSLCFG} \
    -keyout ${PREFIX}server.key  \
    -out ${PREFIX}server.csr \
    -reqexts etcd_v3_req -batch -nodes \
    -subj /CN=$CN

# openssl ca -name etcd_ca -config ${OPENSSLCFG} \
    -out ${PREFIX}server.crt \
    -in ${PREFIX}server.csr \
    -extensions etcd_v3_ca_server -batch

Create the peer certificate request and sign it: (peer.csr and peer.crt)

# openssl req -new -config ${OPENSSLCFG} \
    -keyout ${PREFIX}peer.key \
    -out ${PREFIX}peer.csr \
    -reqexts etcd_v3_req -batch -nodes \
    -subj /CN=$CN

# openssl ca -name etcd_ca -config ${OPENSSLCFG} \
  -out ${PREFIX}peer.crt \
  -in ${PREFIX}peer.csr \
  -extensions etcd_v3_ca_peer -batch

Copy the current etcd configuration and ca.crt files from the current node as examples to modify later:
```
# cp /etc/etcd/etcd.conf ${PREFIX}
# cp /etc/etcd/ca.crt ${PREFIX}
```
While still on the surviving etcd host, add the new host to the cluster. To add additional etcd members to the cluster, you must first adjust the default localhost peer in the peerURLs value for the first member:
1. Get the member ID for the first member using the member list command:
  # etcdctl --cert-file=/etc/etcd/peer.crt \ --key-file=/etc/etcd/peer.key \ --ca-file=/etc/etcd/ca.crt \ --peers="https://172.18.1.18:2379,https://172.18.9.202:2379,https://172.18.0.75:2379" \ (1) member list
  1 Ensure that you specify the URLs of only active etcd members in the --peers parameter value.
2. Obtain the IP address where etcd listens for cluster peers:
  $ ss -l4n | grep 2380
3. Update the value of peerURLs using the etcdctl member update command by passing the member ID and IP address obtained from the previous steps:
  # etcdctl --cert-file=/etc/etcd/peer.crt \ --key-file=/etc/etcd/peer.key \ --ca-file=/etc/etcd/ca.crt \ --peers="https://172.18.1.18:2379,https://172.18.9.202:2379,https://172.18.0.75:2379" \ member update 511b7fb6cc0001 https://172.18.1.18:2380
4. Re-run the member list command and ensure the peer URLs no longer include localhost.

Add the new host to the etcd cluster. Note that the new host is not yet configured, so the status stays as unstarted until the you configure the new host.

You must add each member and bring it online one at a time. When you add each additional member to the cluster, you must adjust the peerURLs list for the current peers. The peerURLs list grows by one for each member added. The etcdctl member add command outputs the values that you must set in the etcd.conf file as you add each member, as described in the following instructions.

# etcdctl -C https://${CURRENT_ETCD_HOST}:2379 \
  --ca-file=/etc/etcd/ca.crt     \
  --cert-file=/etc/etcd/peer.crt     \
  --key-file=/etc/etcd/peer.key member add ${NEW_ETCD_HOSTNAME} https://${NEW_ETCD_IP}:2380 (1)

Added member named 10.3.9.222 with ID 4e1db163a21d7651 to cluster

ETCD_NAME="<NEW_ETCD_HOSTNAME>"
ETCD_INITIAL_CLUSTER="<NEW_ETCD_HOSTNAME>=https://<NEW_HOST_IP>:2380,<CLUSTERMEMBER1_NAME>=https:/<CLUSTERMEMBER2_IP>:2380,<CLUSTERMEMBER2_NAME>=https:/<CLUSTERMEMBER2_IP>:2380,<CLUSTERMEMBER3_NAME>=https:/<CLUSTERMEMBER3_IP>:2380"
ETCD_INITIAL_CLUSTER_STATE="existing"

1	In this line, `10.3.9.222` is a label for the etcd member. You can specify the host name, IP address, or a simple name.

Update the sample ${PREFIX}/etcd.conf file.
1. Replace the following values with the values generated in the previous step:
  - ETCD_NAME
  - ETCD_INITIAL_CLUSTER
  - ETCD_INITIAL_CLUSTER_STATE
2. Modify the following variables with the new host IP from the output of the previous step. You can use ${NEW_ETCD_IP} as the value.
  ETCD_LISTEN_PEER_URLS ETCD_LISTEN_CLIENT_URLS ETCD_INITIAL_ADVERTISE_PEER_URLS ETCD_ADVERTISE_CLIENT_URLS
3. If you previously used the member system as an etcd node, you must overwrite the current values in the /etc/etcd/etcd.conf file.
4. Check the file for syntax errors or missing IP addresses, otherwise the etcd service might fail:
  # vi ${PREFIX}/etcd.conf
On the node that hosts the installation files, update the [etcd] hosts group in the /etc/ansible/hosts inventory file. Remove the old etcd hosts and add the new ones.

Create a tgz file that contains the certificates, the sample configuration file, and the ca and copy it to the new host:

# tar -czvf /etc/etcd/generated_certs/${CN}.tgz -C ${PREFIX} .
# scp /etc/etcd/generated_certs/${CN}.tgz ${CN}:/tmp/

Modify the new etcd host

Install iptables-services to provide iptables utilities to open the required ports for etcd:
```
# yum install -y iptables-services
```
Create the OS_FIREWALL_ALLOW firewall rules to allow etcd to communicate:
- Port 2379/tcp for clients
- Port 2380/tcp for peer communication
  # systemctl enable iptables.service --now # iptables -N OS_FIREWALL_ALLOW # iptables -t filter -I INPUT -j OS_FIREWALL_ALLOW # iptables -A OS_FIREWALL_ALLOW -p tcp -m state --state NEW -m tcp --dport 2379 -j ACCEPT # iptables -A OS_FIREWALL_ALLOW -p tcp -m state --state NEW -m tcp --dport 2380 -j ACCEPT # iptables-save | tee /etc/sysconfig/iptables
  In this example, a new chain OS_FIREWALL_ALLOW is created, which is the standard naming the OpenShift Container Platform installer uses for firewall rules.
  
  If the environment is hosted in an IaaS environment, modify the security groups for the instance to allow incoming traffic to those ports as well.
Install etcd:
```
# yum install -y etcd
```
Ensure version etcd-2.3.7-4.el7.x86_64 or greater is installed,
Ensure the etcd service is not running:
```
# systemctl disable etcd --now
```

Remove any etcd configuration and data:

# rm -Rf /etc/etcd/*
# rm -Rf /var/lib/etcd/*

Extract the certificates and configuration files:

# tar xzvf /tmp/etcd0.example.com.tgz -C /etc/etcd/

Modify the file ownership permissions:

# chown -R etcd:etcd /etc/etcd/*
# chown -R etcd:etcd /var/lib/etcd/

Start etcd on the new host:
```
# systemctl enable etcd --now
```

Verify that the host is part of the cluster and the current cluster health:

If you use the v2 etcd api, run the following command:

# etcdctl --cert-file=/etc/etcd/peer.crt \
          --key-file=/etc/etcd/peer.key \
          --ca-file=/etc/etcd/ca.crt \
          --peers="https://*master-0.example.com*:2379,\
          https://*master-1.example.com*:2379,\
          https://*master-2.example.com*:2379,\
          https://*etcd0.example.com*:2379"\
          cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
member 8b8904727bf526a5 is healthy: got healthy result from https://192.168.55.21:2379
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

If you use the v3 etcd api, run the following command:

# ETCDCTL_API=3 etcdctl --cert="/etc/etcd/peer.crt" \
          --key=/etc/etcd/peer.key \
          --cacert="/etc/etcd/ca.crt" \
          --endpoints="https://*master-0.example.com*:2379,\
            https://*master-1.example.com*:2379,\
            https://*master-2.example.com*:2379,\
            https://*etcd0.example.com*:2379"\
            endpoint health
https://master-0.example.com:2379 is healthy: successfully committed proposal: took = 5.011358ms
https://master-1.example.com:2379 is healthy: successfully committed proposal: took = 1.305173ms
https://master-2.example.com:2379 is healthy: successfully committed proposal: took = 1.388772ms
https://etcd0.example.com:2379 is healthy: successfully committed proposal: took = 1.498829ms

Modify each OpenShift Container Platform master

Modify the master configuration in the etcClientInfo section of the /etc/origin/master/master-config.yaml file on every master. Add the new etcd host to the list of the etcd servers OpenShift Container Platform uses to store the data, and remove any failed etcd hosts:

etcdClientInfo:
  ca: master.etcd-ca.crt
  certFile: master.etcd-client.crt
  keyFile: master.etcd-client.key
  urls:
    - https://master-0.example.com:2379
    - https://master-1.example.com:2379
    - https://master-2.example.com:2379
    - https://etcd0.example.com:2379

Restart the master API service:
- On every master:
  # systemctl restart atomic-openshift-master-api
- Or, on a single master cluster installation:
  # systemctl restart atomic-openshift-master
  The number of etcd nodes must be odd, so you must add at least two hosts.
If you use Flannel, modify the flanneld service configuration located at /etc/sysconfig/flanneld on every OpenShift Container Platform host to include the new etcd host:
```
FLANNEL_ETCD_ENDPOINTS=https://master-0.example.com:2379,https://master-1.example.com:2379,https://master-2.example.com:2379,https://etcd0.example.com:2379
```
Restart the flanneld service:
```
# systemctl restart flanneld.service
```

Removing an etcd host

If an etcd host fails beyond restoration, remove it from the cluster.

Steps to be performed on all masters hosts

Procedure

Remove each other etcd host from the etcd cluster. Run the following command for each etcd node:

# etcdctl -C https://<surviving host IP address>:2379 \
  --ca-file=/etc/etcd/ca.crt     \
  --cert-file=/etc/etcd/peer.crt     \
  --key-file=/etc/etcd/peer.key member remove <failed member ID>

Restart the master API service on every master:
```
# systemctl restart atomic-openshift-master-api
```
Or, if using a single master cluster installation:
```
# systemctl restart atomic-openshift-master
```

Steps to be performed in the current etcd cluster

Procedure

Remove the failed host from the cluster:

# etcdctl2 cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
failed to check the health of member 8372784203e11288 on https://192.168.55.21:2379: Get https://192.168.55.21:2379/health: dial tcp 192.168.55.21:2379: getsockopt: connection refused
member 8372784203e11288 is unreachable: [https://192.168.55.21:2379] are all unreachable
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

# etcdctl2 member remove 8372784203e11288 (1)
Removed member 8372784203e11288 from cluster

# etcdctl2 cluster-health
member 5ee217d19001 is healthy: got healthy result from https://192.168.55.12:2379
member 2a529ba1840722c0 is healthy: got healthy result from https://192.168.55.8:2379
member ed4f0efd277d7599 is healthy: got healthy result from https://192.168.55.13:2379
cluster is healthy

1	The `remove` command requires the etcd ID, not the hostname.

To ensure the etcd configuration does not use the failed host when the etcd service is restarted, modify the /etc/etcd/etcd.conf file on all remaining etcd hosts and remove the failed host in the value for the ETCD_INITIAL_CLUSTER variable:
```
# vi /etc/etcd/etcd.conf
```
For example:
```
ETCD_INITIAL_CLUSTER=master-0.example.com=https://192.168.55.8:2380,master-1.example.com=https://192.168.55.12:2380,master-2.example.com=https://192.168.55.13:2380
```
becomes:
```
ETCD_INITIAL_CLUSTER=master-0.example.com=https://192.168.55.8:2380,master-1.example.com=https://192.168.55.12:2380
```
Restarting the etcd services is not required, because the failed host is removed using etcdctl.
Modify the Ansible inventory file to reflect the current status of the cluster and to avoid issues when re-running a playbook:
```
[OSEv3:children]
masters
nodes
etcd

... [OUTPUT ABBREVIATED] ...

[etcd]
master-0.example.com
master-1.example.com
```
If you are using Flannel, modify the flanneld service configuration located at /etc/sysconfig/flanneld on every host and remove the etcd host:
```
FLANNEL_ETCD_ENDPOINTS=https://master-0.example.com:2379,https://master-1.example.com:2379,https://master-2.example.com:2379
```
Restart the flanneld service:
```
# systemctl restart flanneld.service
```

Adding a host to the cluster

Master host tasks

Deprecating a master host

Creating a master host backup

Procedure

Backing up etcd

Backing up etcd configuration files

Procedure

Backing up etcd data

Prerequisites

Procedure

Deprecating a master host

Procedure

Removing an etcd host

Procedure

Procedure

Creating a master host backup

Procedure

Restoring a master host backup

Procedure

Node host tasks

Deprecating a node host

Prerequisites

Procedure

Replacing a node host

Creating a node host backup

Procedure

Restoring a node host backup

Procedure

Node maintenance and next steps

etcd tasks

etcd backup

Backing up etcd

Backing up etcd configuration files

Procedure

Backing up etcd data

Prerequisites

Procedure

Restoring etcd

Restoring etcd v2 & v3 data

Procedure

Fix the peerURLS parameter

Procedure

Restoring etcd for v3

Procedure

Replacing an etcd host

Scaling etcd

Prerequisites

Adding a new etcd host using Ansible

Procedure

Manually adding a new etcd host

Procedure

Modify the current etcd cluster

Modify the new etcd host

Modify each OpenShift Container Platform master

Removing an etcd host

Procedure

Procedure

Fix the `peerURLS` parameter