public Instance withOs(String os) {
        setOs(os);
        return this;
    }
<p>
The instance's operating system.
</p>

@param os
       The instance's operating system.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-opsworks/src/main/java/com/amazonaws/services/opsworks/model/Instance.java