How to Build, Manage, and Recover an etcd Cluster with TLS on CentOS

Preface

Previously I was not familiar with etcd, so I decided to learn it and recorded the process to help others.

Environment

Three virtual machines running CentOS 7.7 with etcd version 3.4.16 and self‑signed certificates:

IP: 10.211.55.50, Hostname: etcd1

IP: 10.211.55.51, Hostname: etcd2

IP: 10.211.55.52, Hostname: etcd3

1. Cluster Setup

Deploy etcd on the VMs using static configuration, specifying each node in the configuration.

Download, extract, and move etcd binaries to

/usr/local/bin/

and set permissions.

<code># Download address: https://github.com/etcd-io/etcd/releases
wget https://github.com/coreos/etcd/releases/download/v3.4.16/etcd-v3.4.16-linux-amd64.tar.gz
 tar -zxvf etcd-v3.4.16-linux-amd64.tar.gz
cd etcd*
mv etcdctl etcd /usr/local/bin
chmod +x /usr/local/bin/etcd*</code>

Prepare certificate files (

ca-config.json

,

etcd-ca-csr.json

,

etcd-csr.json

).

<code># ca-config.json etcd-ca-csr.json etcd-csr.json
cat ca-config.json
{
  "signing": {
    "default": {"expiry": "876000h"},
    "profiles": {"kubernetes": {"usages": ["signing","key encipherment","server auth","client auth"],"expiry": "876000h"}}
  }
}

cat etcd-ca-csr.json
{
  "CN": "etcd",
  "key": {"algo": "rsa","size": 2048},
  "names": [{"C": "CN","ST": "Shenzhen","L": "Shenzhen","O": "etcd","OU": "Etcd Security"}]
}

cat etcd-csr.json
{
  "CN": "etcd",
  "hosts": ["127.0.0.1","10.211.55.50","10.211.55.51","10.211.55.52"],
  "key": {"algo": "rsa","size": 2048},
  "names": [{"C": "CN","ST": "Shenzhen","L": "Shenzhen","O": "etcd","OU": "Etcd Security"}]
}</code>

Generate the etcd CA certificate.

<code>cfssl gencert -initca etcd-ca-csr.json | cfssljson -bare etcd-ca
# List generated files
ls -al</code>

Generate the etcd server certificate.

<code>cfssl gencert -ca=etcd-ca.pem -ca-key=etcd-ca-key.pem -config=ca-config.json -profile=kubernetes etcd-csr.json | cfssljson -bare etcd
# List generated files
ls -al</code>

Copy certificates to the etcd SSL directory and distribute to other nodes.

<code>mkdir -pv /etc/etcd/ssl && cp etcd*.pem /etc/etcd/ssl
scp -r /etc/etcd root@etcd2:/etc/etcd
scp -r /etc/etcd root@etcd3:/etc/etcd</code>

Create a systemd service file for etcd (modify IP and name per node).

<code>[Unit]
Description=Etcd Server
After=network.target network-online.target
Wants=network-online.target
Documentation=https://github.com/coreos
[Service]
Type=notify
WorkingDirectory=/var/lib/etcd/
EnvironmentFile=-/etc/etcd/etcd.conf
ExecStart=/usr/local/bin/etcd \
  --name=etcd1 \
  --cert-file=/etc/etcd/ssl/etcd.pem \
  --key-file=/etc/etcd/ssl/etcd-key.pem \
  --peer-cert-file=/etc/etcd/ssl/etcd.pem \
  --peer-key-file=/etc/etcd/ssl/etcd-key.pem \
  --trusted-ca-file=/etc/etcd/ssl/etcd-ca.pem \
  --peer-trusted-ca-file=/etc/etcd/ssl/etcd-ca.pem \
  --initial-advertise-peer-urls=https://10.211.55.50:2380 \
  --listen-peer-urls=https://10.211.55.50:2380 \
  --listen-client-urls=https://10.211.55.50:2379,http://127.0.0.1:2379 \
  --advertise-client-urls=https://10.211.55.50:2379 \
  --initial-cluster-token=etcd-cluster-0 \
  --initial-cluster=etcd1=https://10.211.55.50:2380,etcd2=https://10.211.55.51:2380,etcd3=https://10.211.55.52:2380 \
  --initial-cluster-state=new \
  --data-dir=/var/lib/etcd
Restart=on-failure
RestartSec=5
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target</code>

Start etcd on all three nodes.

<code>systemctl daemon-reload && systemctl enable etcd && systemctl start etcd</code>

Check cluster status:

<code># List members
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.52:2379 member list -w table
# Verify leader and write a key
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 put foo4 bar4
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 get foo4</code>

2. Member Changes

Remove a Member

Because of limited resources, we first simulate member removal.

<code># Get member IDs
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 endpoint status -w table
# Remove etcd3 (ID ca2cb14b2acc776)
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379 member remove ca2cb14b2acc776
# Verify remaining members
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379 endpoint status -w table</code>

Add a Member

Add a new node by first using

etcdctl

then updating the service file.

<code># Add member etcd3
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379 member add etcd3 --peer-urls="https://10.211.55.52:2380"
# Update etcd.service on the new node
[Unit]
Description=Etcd Server
...
ExecStart=/usr/local/bin/etcd \
  --name=etcd3 \
  --cert-file=/etc/etcd/ssl/etcd.pem \
  --key-file=/etc/etcd/ssl/etcd-key.pem \
  --peer-cert-file=/etc/etcd/ssl/etcd.pem \
  --peer-key-file=/etc/etcd/ssl/etcd-key.pem \
  --trusted-ca-file=/etc/etcd/ssl/etcd-ca.pem \
  --peer-trusted-ca-file=/etc/etcd/ssl/etcd-ca.pem \
  --initial-advertise-peer-urls=https://10.211.55.52:2380 \
  --listen-peer-urls=https://10.211.55.52:2380 \
  --listen-client-urls=https://10.211.55.52:2379,http://127.0.0.1:2379 \
  --advertise-client-urls=https://10.211.55.52:2379 \
  --initial-cluster-token=etcd-cluster-0 \
  --initial-cluster=etcd1=https://10.211.55.50:2380,etcd2=https://10.211.55.51:2380,etcd3=https://10.211.55.52:2380 \
  --initial-cluster-state=existing \
  --data-dir=/var/lib/etcd
# Start the new member
systemctl start etcd && systemctl status etcd
# Verify cluster status
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 endpoint status -w table</code>

3. Data Backup

Perform a manual snapshot for testing purposes.

<code># Write a test key
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 put xiyangxixi boys
# Create snapshot
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379 snapshot save snapshot-xiyangxixi.db</code>

4. Cluster Data Recovery

Restore the cluster from the same snapshot file on each node.

<code># On etcd1
etcdctl snapshot restore /root/snapshot-xiyangxixi.db \
  --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem \
  --name etcd1 \
  --initial-advertise-peer-urls=https://10.211.55.50:2380 \
  --initial-cluster-token=etcd-cluster-1 \
  --initial-cluster=etcd1=https://10.211.55.50:2380,etcd2=https://10.211.55.51:2380,etcd3=https://10.211.55.52:2380
# Repeat on etcd2 and etcd3 with appropriate --name and --initial-advertise-peer-urls
# Reload systemd and start etcd on each node
systemctl daemon-reload && systemctl start etcd
# Verify restored data
etcdctl --cacert /etc/etcd/ssl/etcd-ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem --endpoints=https://10.211.55.50:2379,https://10.211.55.51:2379,https://10.211.55.52:2379 get xiyangxixi</code>

References

https://etcd.io/docs/v3.4/op-guide/hardware/

https://etcd.io/docs/v3.4/op-guide/recovery/

https://etcd.io/docs/v3.4/op-guide/clustering/