# Version

The `version` section configures how Atmos handles version management, including automatic update checking, version constraint enforcement, Atmos self-management, and Atmos-managed software versions.

## Configuration

**File:** `atmos.yaml`

```yaml
version:
  # Pin project to a specific Atmos version
  use: "1.199.0"

  # Automatic update checking
  check:
    enabled: true
    frequency: daily

  # Version constraint enforcement
  constraint:
    require: ">=1.100.0"
    enforcement: fatal
    message: "Please upgrade Atmos to use this configuration."

  # Managed software versions
  track: prod
  lock_file: versions.lock.yaml
  providers:
    dockerhub:
      kind: docker
      url: registry-1.docker.io
  defaults:
    update:
      strategy: patch
      cooldown: 14d
  groups:
    infrastructure:
      ecosystems: [toolchain, github/actions, oci]
      update:
        strategy: minor
  tracks:
    prod:
      dependencies:
        checkout:
          ecosystem: github/actions
          package: actions/checkout
          desired: v6
          update:
            pin: sha
  dependencies:
    opentofu:
      ecosystem: toolchain
      datasource: toolchain
      package: opentofu
      desired: "~1.10"
  files:
    - manager: github-actions
      paths:
        - .github/workflows/*.yaml
```

## Version Sections

| Section | Description |
|---------|-------------|
| [Use](/cli/configuration/version/use) | Pin project to a specific Atmos version |
| [Check](/cli/configuration/version/check) | Automatic version checking and update notifications |
| [Constraint](/cli/configuration/version/constraint) | Enforce Atmos version requirements for your configuration |
| [Managed Versions](/cli/configuration/version/managed-versions) | Manage software versions whether Atmos installs them locally or only tracks and renders them into files |
| [Providers](/cli/configuration/version/providers) | Configure version lookup backends such as GitHub, Docker Hub, OCI registries, and ECR |
| [Defaults](/cli/configuration/version/defaults) | Set shared update policy, include/exclude rules, prerelease handling, and labels |
| [Groups](/cli/configuration/version/groups) | Batch related version updates under shared policies |
| [Dependencies](/cli/configuration/version/dependencies) | Define the base catalog of software versions Atmos tracks |
| [Tracks](/cli/configuration/version/tracks) | Override catalog entries per environment or release lane |
| [Files](/cli/configuration/version/files) | Configure file managers that render locked versions into project files |
| [Lock File](/cli/configuration/version/lock-file) | Configure and understand `versions.lock.yaml` |

## Environment Variables

- **`ATMOS_USE_VERSION`**
  Specify which version of Atmos to use. Env var equivalent of 
  `--use-version`
   flag.
- **`ATMOS_VERSION_USE`**
  Internal env var set by the 
  `--use-version`
   flag. Highest precedence in version resolution.
- **`ATMOS_VERSION`**
  Convenience alias matching 
  `tfenv`
  /
  `goenv`
   conventions. Lower precedence than 
  `ATMOS_VERSION_USE`
  .
- **`ATMOS_VERSION_CHECK_ENABLED`**
  Enable or disable automatic version checking.
- **`ATMOS_VERSION_ENFORCEMENT`**
  Override version constraint enforcement level: 
  `fatal`
  , 
  `warn`
  , or 
  `silent`
  .

## See Also

- [CLI Configuration](/cli/configuration) — Overview of CLI configuration
- [`atmos version`](/cli/commands/version/usage) — Display version and check for updates
- [`atmos version track`](/cli/commands/version/track) — Manage external version tracks and locks
- [Atmos Version Management](/howto/atmos-version-management) — How-to guide with profiles