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How to configure docker TLS certs

1. Generating the certs

Refer to the comment from BMitch 1, I wrote the shell script make-certs for generating the certs for both client and server sides.

curl -sSL -o make-certs https://raw.githubusercontent.com/cloudecho/util-script/master/cert/make-certs
chmod +x make-certs

Use the script to generate the certs.

Let's say the server dns name is echoyun.demo, and the server ip is 192.168.10.3

./make-certs -d3650 -J/CN=echoyun.demo -Sechoyun.demo -H192.168.10.3

2. Configuration of the client-side

cd echoyun.demo
mkdir -p ~/.docker/certs
sudo cp client-cert.pem ~/.docker/certs/cert.pem
sudo cp client-key.pem ~/.docker/certs/key.pem 
sudo cp ca.pem ~/.docker/certs/ca.pem 

Configure the envrionment variables by editing ~/.bash_profile or ~/.profile

export DOCKER_TLS_VERIFY="1"
export COMPOSE_TLS_VERSION=TLSv1_2
export DOCKER_HOST="tcp://echoyun.demo:2376"
configure /etc/hosts if need
192.168.10.3  echoyun.demo

3. Configuration of the server-side

Copy the three files to the server which the docker daemon is runing on

  • ca.pem
  • server-cert.pem
  • server-key.pem

and put them under a diretory e.g. /var/lib/docker/certs/

Then configure the docker daemon:

sudo mkdir -p /etc/systemd/system/docker.service.d

cat <<EOF | sudo tee /etc/systemd/system/docker.service.d/docker.conf 
[Service]
ExecStart=
ExecStart=/usr/bin/dockerd --containerd=/run/containerd/containerd.sock
EOF

cat <<EOF | sudo tee /etc/docker/daemon.json 
{
  "tls": true,
  "tlscacert": "/var/lib/docker/certs/ca.pem",
  "tlscert": "/var/lib/docker/certs/server-cert.pem",
  "tlskey": "/var/lib/docker/certs/server-key.pem",
  "hosts": ["fd://", "tcp://0.0.0.0:2376"]
} 
EOF

Remember to enable and start containerd if it hasn't been started:

sudo systemctl enable containerd
sudo systemctl start containerd
systemctl status containerd

Finally, restart docker daemon:

sudo systemctl daemon-reload
sudo systemctl restart docker
systemctl status docker

4. Testing on the client

$ docker info
... ...

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 15
 Server Version: 20.10.11
 ... ...

Reference

  1. https://stackoverflow.com/questions/38286564/docker-tls-verify-docker-host-and-docker-cert-path-on-ubuntu
  2. https://blog.cadena-it.com/linux-tips-how-to/configuring-ssl-requests-with-subjectaltname-with-openssl/

Last update: 2022-01-01
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