Customizing the etcd unit

The etcd systemd unit can be customized by overriding the unit that ships with the default Flatcar Container Linux settings. Common use-cases for doing this are covered below.

Use client certificates

etcd supports client certificates as a way to provide secure communication between clients ↔ leader and internal traffic between etcd peers in the cluster. Configuring certificates for both scenarios is done through a Butane Config. Options provided here will augment the unit that ships with Flatcar Container Linux.

Please follow the instructions on how to create self-signed certificates and private keys.

Note that more etcd settings are needed for a proper configuration.

variant: flatcar
version: 1.0.0
systemd:
 units:
   - name: etcd-member.service
     enabled: true
     dropins:
       - name: 20-clct-etcd-member.conf
         contents: |
           [Service]
           ExecStart=
           ExecStart=/usr/lib/coreos/etcd-wrapper $ETCD_OPTS \
             --ca-file="/path/to/CA.pem" \
             --cert-file="/path/to/server.crt" \
             --key-file="/path/to/server.key" \
             --peer-ca-file="/path/to/CA.pem" \
             --peer-cert-file="/path/to/peers.crt" \
             --peer-key-file="/path/to/peers.key"           

storage:
  files:
    - path: /path/to/CA.pem
      mode: 0644
      contents:
        inline: |
          -----BEGIN CERTIFICATE-----
          MIIFNDCCAx6gAwIBAgIBATALBgkqhkiG9w0BAQUwLTEMMAoGA1UEBhMDVVNBMRAw
          ...snip...
          EtHaxYQRy72yZrte6Ypw57xPRB8sw1DIYjr821Lw05DrLuBYcbyclg==
          -----END CERTIFICATE-----          
    - path: /path/to/server.crt
      mode: 0644
      contents:
        inline: |
          -----BEGIN CERTIFICATE-----
          MIIFWTCCA0OgAwIBAgIBAjALBgkqhkiG9w0BAQUwLTEMMAoGA1UEBhMDVVNBMRAw
          DgYDVQQKEwdldGNkLWNhMQswCQYDVQQLEwJDQTAeFw0xNDA1MjEyMTQ0MjhaFw0y
          ...snip...
          rdmtCVLOyo2wz/UTzvo7UpuxRrnizBHpytE4u0KgifGp1OOKY+1Lx8XSH7jJIaZB
          a3m12FMs3AsSt7mzyZk+bH2WjZLrlUXyrvprI40=
          -----END CERTIFICATE-----          
    - path: /path/to/server.key
      mode: 0644
      contents:
        inline: |
          -----BEGIN RSA PRIVATE KEY-----
          Proc-Type: 4,ENCRYPTED
          DEK-Info: DES-EDE3-CBC,069abc493cd8bda6

          TBX9mCqvzNMWZN6YQKR2cFxYISFreNk5Q938s5YClnCWz3B6KfwCZtjMlbdqAakj
          ...snip...
          mgVh2LBerGMbsdsTQ268sDvHKTdD9MDAunZlQIgO2zotARY02MLV/Q5erASYdCxk
          -----END RSA PRIVATE KEY-----          
    - path: /path/to/peers.crt
      mode: 0644
      contents:
        inline: |
          -----BEGIN CERTIFICATE-----
          VQQLEwJDQTAeFw0xNDA1MjEyMTQ0MjhaFw0yMIIFWTCCA0OgAwIBAgIBAjALBgkq
          DgYDVQQKEwdldGNkLWNhMQswCQYDhkiG9w0BAQUwLTEMMAoGA1UEBhMDVVNBMRAw
          ...snip...
          BHpytE4u0KgifGp1OOKY+1Lx8XSH7jJIaZBrdmtCVLOyo2wz/UTzvo7UpuxRrniz
          St7mza3m12FMs3AsyZk+bH2WjZLrlUXyrvprI90=
          -----END CERTIFICATE-----          
    - path: /path/to/peers.key
      mode: 0644
      contents:
        inline: |
          -----BEGIN RSA PRIVATE KEY-----
          Proc-Type: 4,ENCRYPTED
          DEK-Info: DES-EDE3-CBC,069abc493cd8bda6

          SFreNk5Q938s5YTBX9mCqvzNMWZN6YQKR2cFxYIClnCWz3B6KfwCZtjMlbdqAakj
          ...snip...
          DvHKTdD9MDAunZlQIgO2zotmgVh2LBerGMbsdsTQ268sARY02MLV/Q5erASYdCxk
          -----END RSA PRIVATE KEY-----