--- layout: "docs" page_title: "Commands: Connect Proxy" sidebar_current: "docs-commands-connect-envoy" description: > The connect proxy subcommand is used to run the built-in mTLS proxy for Connect. --- # Consul Connect Envoy Command: `consul connect envoy` The connect Envoy command is used to generate a bootstrap configuration for [Envoy proxy](https://envoyproxy.io) for use with [Consul Connect](/docs/connect/). The default behaviour is to generate the necessary bootstrap configuration for Envoy based on the environment variables and options provided and by taking to the local Consul agent. It `exec`s an external Envoy binary with that configuration leaving the Envoy process running in the foreground. An error is returned on operating systems other than linux or macOS since Envoy does not build for other platforms currently. If the `-bootstrap` option is specified, the bootstrap config is generated in the same way and then printed to stdout. This allows it to be redirected to a file and used with `envoy -c bootstrap.json`. This works on all operating systems allowing configuration to be generated on a host that Envoy doesn't build on but then used in a virtualized environment that can run Envoy. ## Usage Usage: `consul connect envoy [options] [-- pass-through options]` #### API Options The standard API options are used to connect to the local agent to discover the proxy configuration needed. - `-grpc-addr=` - Address of the Consul agent with `grpc` port. This can be an IP address or DNS address, but it must include the port. This can also be specified via the CONSUL_GRPC_ADDR environment variable. In Consul 1.3 and later, the default value is http://127.0.0.1:8502, and https can optionally be used instead. The scheme can also be set to HTTPS by setting the environment variable CONSUL_HTTP_SSL=true. This may be a unix domain socket using `unix:///path/to/socket` if the [agent is configured to listen](/docs/agent/options.html#addresses) that way. -> **Note:** gRPC uses the same TLS settings as the HTTPS API. If HTTPS is enabled then gRPC will require HTTPS as well. <%= partial "docs/commands/http_api_options_client" %> #### Envoy Options * `-sidecar-for` - The _ID_ (not name if they differ) of the service instance this proxy will represent. The target service doesn't need to exist on the local agent yet but a [sidecar proxy registration](/docs/connect/proxies.html#sidecar-proxy-fields) with `proxy.destination_service_id` equal to the passed value must be present. If multiple proxy registrations targeting the same local service instance are present the command will error and `-proxy-id` should be used instead. * `-proxy-id` - The [proxy service](/docs/connect/proxies.html#proxy-service-definitions) ID on the local agent. This must already be present on the local agent. -> **Note:** If ACLs are enabled, a token granting `service:write` for the _target_ service (configured in `proxy.destination_service_name`) must be passed using the `-token` option or `CONSUL_HTTP_TOKEN` environment variable. This token authorizes the proxy to obtain TLS certificates representing the target service. * `-envoy-binary` - The full path to a specific Envoy binary to exec. By default the current `$PATH` is searched for `envoy`. * `-admin-bind` - The `host:port` to bind Envoy's admin HTTP API. Default is `localhost:19000`. Envoy requires that this be enabled. The host part must be resolvable DNS name or IP address. * `-bootstrap` - If present, the command will simply output the generated bootstrap config to stdout in JSON protobuf form. This can be directed to a file and used to start Envoy with `envoy -c bootstrap.json`. ~> **Security Note:** If ACLs are enabled the bootstrap JSON will contain the ACL token from `-token` or the environment and so should be handled as a secret. This token grants the identity of any service it has `service:write` permission for and so can be used to access any upstream service that that service is allowed to access by [Connect intentions](/docs/connect/intentions.html). * `-- [pass-through options]` - Any options given after a double dash are passed directly through to the `envoy` invocation. See [Envoy's documentation](https://www.envoyproxy.io/docs) for more details. The command always specifies `--config-file` and `--v2-config-only` and by default passes `--disable-hot-restart` see [hot restart](#hot-restart). ## Examples Assume a local service instance is registratered on the local agent with a sidecar proxy (using the [sidecar service registration](/docs/connect/proxies/sidecar-service.html) helper) as below. ```hcl service { name = "web" port = 8080 connect { sidecar_service {} } } ``` The sidecar Envoy process can be started with. ```text $ consul connect envoy -sidecar-for web ``` This example assumes that the correct [environment variables](#api-options) are used to set the local agent connection information and ACL token, or that the agent is using all-default configuration. To pass additional arguments directly to Envoy, for example output logging level, you can use: ```text $ consul connect envoy -sidecar-for web -- -l debug ``` To run multiple different proxy instances on the same host, you will need to use `-admin-bind` on all but one to ensure they don't attempt to bind to the same port as in the following example. ```text $ consul connect envoy -sidecar-for db -admin-bind localhost:19001 ``` ## Exec Security Details The command needs to pass the bootstrap config through to Envoy. Envoy currently only supports passing this as a file path or passing a whole string on the command line with `--config-yaml`. Since the bootstrap needs to contain the ACL token to authorize the proxy, this secret needs careful handling. Passing a secret via command option is unacceptable as on many unix systems these are readable to any user on the host for example via `/proc` or via a setuid process like `ps`. Creating a temporary file is more secure in that it can only be read by the current user but risks leaving secret material on disk for an unbounded length of time and in a location that is opaque to the operator. To work around these issues, the command currently creates a temporary file and immediately unlinks it so it can't be read by any other process that doesn't already have the file descriptor. It then writes the bootstrap JSON, and unsets the CLOEXEC bit on the file handle so that it remains available to the Envoy process after exec. Finally it `exec`s Envoy with `--config-file /dev/fd/X` where `X` is the the file descriptor number of the temp file. This ensures that Envoy can read the file without any other normal user process being able to (assuming they don't have privileged access to /proc). Once the Envoy process stops, there is no longer any reference to the file to clean up. ## Envoy Hot Restart Envoy supports hot restart which requires simple external coordination. By default, this command will add `--disable-hot-restart` when it runs Envoy. The reason for this default behavior is to make it easy to test and run local demonstrations with multiple Envoy instances outside of cgroups or network namespaces. To use hot restart, Envoy needs to be started with either the `--restart-epoch` option. If this command detects that option in the pass-through flags it will _not_ add `--disable-hot-restart` allowing hot restart to work normally. The only difference to note over running Envoy directly is that `--restart-epoch` must be explicitly set to `0` for the initial launch of the Envoy instance to avoid disabling hot restart entirely. The official `hot-restarter.py` always sets this option so should work as recommended.