# Prerequisites for OpenSSL Dynamic Engine with AWS CloudHSM Client SDK 3 For information about platform support, see [AWS CloudHSM Client SDK 3 supported platforms](sdk3-support.md). Before you can use the AWS CloudHSM dynamic engine for OpenSSL with Client SDK 3, you need the AWS CloudHSM client. The client is a daemon that establishes end-to-end encrypted communication with the HSMs in your cluster, and the OpenSSL engine communicates locally with the client. To install and configure the AWS CloudHSM client, see [Install the client (Linux)](cmu-install-and-configure-client-linux.md). Then use the following command to start it. ------ #### [ Amazon Linux ] ``` $ sudo start cloudhsm-client ``` ------ #### [ Amazon Linux 2 ] ``` $ sudo systemctl start cloudhsm-client ``` ------ #### [ CentOS 6 ] ``` $ sudo systemctl start cloudhsm-client ``` ------ #### [ CentOS 7 ] ``` $ sudo systemctl start cloudhsm-client ``` ------ #### [ RHEL 6 ] ``` $ sudo systemctl start cloudhsm-client ``` ------ #### [ RHEL 7 ] ``` $ sudo systemctl start cloudhsm-client ``` ------ #### [ Ubuntu 16.04 LTS ] ``` $ sudo systemctl start cloudhsm-client ``` ------