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====== docker ======
Connect to Container as root
<code>
$ docker exec -u 0 -it FW_pgAdmin4 /bin/ash
</code>

PostgreSQL DEV refresh
<code>
docker exec -it dev-container_devcontainer_db_1 /bin/bash
</code>

View filesystem
<code>
docker image save fueltracker_app >image.tgz
</code>

===== SSL/TLS connection =====

==== Generate a CA, server, and client certificate/key pair ====

1. Create a working directory

mkdir -p ~/.docker/tls && cd ~/.docker/tls

2. Generate the CA private key

openssl genrsa -aes256 -out ca-key.pem 4096

3. Generate the CA certificate

openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem

You'll be prompted for a passphrase and subject info (Country, CN, etc.).

4. Generate the server private key

openssl genrsa -out server-key.pem 4096

5. Generate the server CSR (Certificate Signing Request)

openssl req -subj "/CN=<your-server-hostname-or-IP>" -sha256 -new -key server-key.pem -out server.csr

Replace <your-server-hostname-or-IP> with your Docker host's hostname or IP (e.g., mydockerhost or 192.168.1.10).

6. Create a SANs (Subject Alternative Names) extension file

echo subjectAltName = DNS:<hostname>,IP:<IP>,IP:127.0.0.1 > extfile.cnf
  echo extendedKeyUsage = serverAuth >> extfile.cnf

Add all hostnames/IPs clients will use to reach the server.

7. Sign the server certificate with the CA

openssl x509 -req -days 365 -sha256 \
    -in server.csr -CA ca.pem -CAkey ca-key.pem \
    -CAcreateserial -out server-cert.pem -extfile extfile.cnf

8. Generate the client private key

openssl genrsa -out key.pem 4096

9. Generate the client CSR

openssl req -subj '/CN=client' -new -key key.pem -out client.csr

10. Create a client extension file

echo extendedKeyUsage = clientAuth > extfile-client.cnf

11. Sign the client certificate with the CA

openssl x509 -req -days 365 -sha256 \
    -in client.csr -CA ca.pem -CAkey ca-key.pem \
    -CAcreateserial -out cert.pem -extfile extfile-client.cnf

12. Clean up CSRs and extension files, lock down permissions

rm -f client.csr server.csr extfile.cnf extfile-client.cnf
  chmod 0400 ca-key.pem key.pem server-key.pem
  chmod 0444 ca.pem server-cert.pem cert.pem

After this you'll have:

┌──────────────────────────────────┬───────────────────────────────────────────────────┐
  │               File               │                      Purpose                      │
  ├──────────────────────────────────┼───────────────────────────────────────────────────┤
  │ ca.pem                           │ CA certificate (needed by both server and client) │
  ├──────────────────────────────────┼───────────────────────────────────────────────────┤
  │ server-cert.pem / server-key.pem │ Server certificate and key                        │
  ├──────────────────────────────────┼───────────────────────────────────────────────────┤
  │ cert.pem / key.pem               │ Client certificate and key                        │
  └──────────────────────────────────┴───────────────────────────────────────────────────┘

==== Configure /etc/docker/daemon.json with "tls": true, "tlscacert", "tlscert", and "tlskey" ====

1. Copy server certs to a permanent location

sudo mkdir -p /etc/docker/certs
  sudo cp ~/.docker/tls/ca.pem /etc/docker/certs/
  sudo cp ~/.docker/tls/server-cert.pem /etc/docker/certs/
  sudo cp ~/.docker/tls/server-key.pem /etc/docker/certs/
  sudo chmod 0444 /etc/docker/certs/ca.pem /etc/docker/certs/server-cert.pem
  sudo chmod 0400 /etc/docker/certs/server-key.pem

2. Create or edit /etc/docker/daemon.json

sudo tee /etc/docker/daemon.json > /dev/null <<EOF
  {
    "tls": true,
    "tlsverify": true,
    "tlscacert": "/etc/docker/certs/ca.pem",
    "tlscert": "/etc/docker/certs/server-cert.pem",
    "tlskey": "/etc/docker/certs/server-key.pem",
    "hosts": ["unix:///var/run/docker.sock", "tcp://0.0.0.0:2376"]
  }
  EOF

- "tls": true — enables TLS but allows unauthenticated clients
  - "tlsverify": true — enforces mutual TLS (clients must present a valid cert)
  - Port 2376 is the standard TLS Docker port (2375 is unencrypted)

3. Handle the hosts conflict with systemd (WSL/Linux)

If Docker is managed by systemd, the -H flag in the service file conflicts with hosts in daemon.json. Override it:

sudo mkdir -p /etc/systemd/system/docker.service.d
  sudo tee /etc/systemd/system/docker.service.d/override.conf > /dev/null <<EOF
  [Service]
  ExecStart=
  ExecStart=/usr/bin/dockerd
  EOF

4. Reload and restart Docker

sudo systemctl daemon-reload
  sudo systemctl restart docker

5. Verify Docker is listening on port 2376

sudo ss -tlnp | grep 2376

You should see dockerd bound to 0.0.0.0:2376. That confirms TLS is active and the daemon is accepting remote connections.

===== References =====
Docker Exec Command With Examples - https://devconnected.com/docker-exec-command-with-examples/

Exploring Docker container's file system - https://stackoverflow.com/questions/20813486/exploring-docker-containers-file-system
{{tag>[Docker]}}

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