* **Config Files Require an Extension:** As part of supporting the [HCL](https://github.com/hashicorp/hcl#syntax) format for Consul's config files, an `.hcl` or `.json` extension is required for all config files loaded by Consul, even when using the [`-config-file`](https://www.consul.io/docs/agent/options.html#_config_file) argument to specify a file directly. [GH-3480]
* **Deprecated Options Have Been Removed:** All of Consul's previously deprecated command line flags and config options have been removed, so these will need to be mapped to their equivalents before upgrading. [GH-3480]
<details><summary>Detailed List of Deprecated Options and their Equivalents</summary>
<details><summary>Detailed List of Removed Options and their Equivalents</summary>
| Option | Supported Equivalent |
| -------- | -------------------- |
| Removed Option | Equivalent |
| -------------- | ---------- |
| `-atlas` | None, Atlas is no longer supported. |
| `-atlas-token`| None, Atlas is no longer supported. |
| `-atlas-join` | None, Atlas is no longer supported. |