.NET Core 2.1.0 Preview 2 is available for download and usage in your environment. Have a look at the [Known Issues](2.1.0-preview2-known-issues.md) document as there are a few things to be aware of before installing.
The .NET Core SDK 2.1 Preview includes .NET Core 2.1 Runtime Preview so downloading the runtime packages separately is not needed when installing the SDK. After installing the .NET Core SDK 2.1 Preview, the following command will show that you're running version `2.1.300-preview2-008530` of the tools.
Your feedback is important and appreciated. We've created an issue at [dotnet/core #1422](https://github.com/dotnet/core/issues/1422) for your questions and comments.
The [.NET Core Docker images](https://hub.docker.com/r/microsoft/dotnet/) have been updated for this release. Look for the 2.1 Preview 2 images.
## Azure AppServices
Details for running .NET Core 2.1 Preview 1 in Azure App Services can be seen in the [ASP.NET Core blog post](https://blogs.msdn.microsoft.com/webdev/2018/02/27/asp-net-core-2-1-0-preview1-using-asp-net-core-previews-on-azure-app-service/).
## Notable Additions in Preview 2
### Breaking API changes
Many APIs received updates from Preview 1 which are considered breaking changes. Please review the API diff to determine if any will impact existing projects build on 2.1.0 Preview 1.
### System.Security
| Area | Description | Details |
| ---- | ----------- | ------- |
| System.Security | Added CryptographicOperations class | CryptographicOperations.FixedTimeEquals takes a fixed amount of time to return for any two inputs of the same length, making it suitable for use in cryptographic verification to avoid contributing to timing side-channel information. CryptographicOperations.ZeroMemory is a memory clearing routine which cannot be optimized away via a write-without-subsequent-read optimization. |
| System.Security | Added static RandomNumberGenerator.Fill | The static RandomNumberGenerator.Fill will fill a Span with random values using the system-preferred CSPRNG, and does not require the caller to manage the lifetime of an IDisposable resource. |
| System.Security | Added support for RFC 3161 cryptographic timestamps | New API to request, read, validate, and create TimestampToken values as defined by RFC 3161. |
| System.Security | Unix EnvelopedCms | The EnvelopedCms class is now available on Linux and macOS. |
| System.Security | Added ECDiffieHellman | Elliptic-Curve Diffie-Hellman (ECDH) is now available on .NET Core via the ECDiffieHellman class family with the same surface area as .NET Framework 4.7. |
| System.Security | Added RSA-OAEP-SHA2 and RSA-PSS to Unix platforms | Starting with this release the instance provided by RSA.Create() on .NET Core can always encrypt or decrypt with OAEP using a SHA-2 digest, as well as generate or validate signatures using RSA-PSS. |
### Global Tools
Global tools let you install a tool from a NuGet feed into your local path. This makes in available in a similar manner to npm -g.
**dotnet --list-sdks**
`dotnet --list-sdks` provides a list of .NET Core SDKs installed on the machine
Many .NET Core SDKs may be installed on a given machine. The new `--list-sdks` switch lists installed SDKs along with the base path where they are installed. This new switch is present in the .NET Core host, which has a single copy on the machine. Thus, this switch works once the preview is installed, regardless of global.json or if the preview is uninstalled.
**dotnet --list-runtimes**
`dotnet --list-runtimes` provides a list of .NET Core Runtimes installed on the machine
Many .NET Core Runtimes may be installed on a given machine. The new `--list-runtimes` switch lists installed runtimes along with the base path where they are installed. This new switch is present in the .NET Core host, which has a single copy on the machine. Thus, this switch works once the preview is installed, regardless of global.json or if the preview is uninstalled.
