​
Appending the Certificate Authority of MITM Proxies

Put into each machine the PEM encoded certificate: 
machine:
  ...
  files:
    - content: |
        -----BEGIN CERTIFICATE-----
        ...
        -----END CERTIFICATE-----
      permissions: 0644
      path: /etc/ssl/certs/ca-certificates
      op: append

​
Configuring a Machine to Use the Proxy

To make use of a proxy: 
machine:
  env:
    http_proxy: <http proxy>
    https_proxy: <https proxy>
    no_proxy: <no proxy>
Additionally, configure the DNS nameservers, and NTP servers: 
machine:
  env:
  ...
  time:
    servers:
      - <server 1>
      - <server ...>
      - <server n>
  ...
  network:
    nameservers:
      - <ip 1>
      - <ip ...>
      - <ip n>
If a proxy is required before Talos machine configuration is applied, use kernel command line arguments: 
talos.environment=http_proxy=<http-proxy> talos.environment=https_proxy=<https-proxy>