To give multiple users shared, secure access to the same data, you can set a volume to read-only access. Run the following command to set a volume to read-only access: $ cinder readonly-mode-update VOLUME BOOLEAN VOLUME is the ID of the target volume and BOOLEAN is a flag that enables read-only or read/write access to the volume. The following values for BOOLEAN are valid: true. Sets the read-only flag in the volume. When you attach the volume to an instance, the instance checks for this flag to determine whether to restrict volume access to read-only. false. Sets the volume to read/write access.