You can add arguments to the end of the docker run command. docker run codercom/code-server --disable-file-downloads for example.

I do not believe systemd will read that coder.env file, will it? You probably have to set the environment variable in the service configuration file. For example:

[Service]
Environment=CS_DISABLE_FILE_DOWNLOADS=true

Except, I misread, you are starting Coder with systemd, not code-server, right? I think environment variables set on coderd will not propagate to the workspace agent.

How are you starting code-server? Are you using the module? If so, I am not sure there is a way to configure this. The module will have to be modified to support the flag.

But if you are not using the module and launching code-server yourself, you can just add the flag. For example:

resource "coder_agent" "main" {
  arch           = data.coder_provisioner.me.arch
  os             = "linux"
  startup_script = <<-EOT
    set -e
    curl -fsSL https://code-server.dev/install.sh | sh -s -- --method=standalone --prefix=/tmp/code-server
    /tmp/code-server/bin/code-server --auth none --port 13337 --disable-file-downloads >/tmp/code-server.log 2>&1 &
  EOT

Also note that this flag is for code-server only, it does not affect VS Code desktop.