public String getOs() {
        return this.os;
    }
<p>
The instance's operating system, which must be set to one of the following.
</p>
<ul>
<li>
<p>
A supported Linux operating system: An Amazon Linux version, such as <code>Amazon Linux 2</code>,
<code>Amazon Linux 2018.03</code>, <code>Amazon Linux 2017.09</code>, <code>Amazon Linux 2017.03</code>,
<code>Amazon Linux 2016.09</code>, <code>Amazon Linux 2016.03</code>, <code>Amazon Linux 2015.09</code>, or
<code>Amazon Linux 2015.03</code>.
</p>
</li>
<li>
<p>
A supported Ubuntu operating system, such as <code>Ubuntu 18.04 LTS</code>, <code>Ubuntu 16.04 LTS</code>,
<code>Ubuntu 14.04 LTS</code>, or <code>Ubuntu 12.04 LTS</code>.
</p>
</li>
<li>
<p>
<code>CentOS Linux 7</code>
</p>
</li>
<li>
<p>
<code>Red Hat Enterprise Linux 7</code>
</p>
</li>
<li>
<p>
A supported Windows operating system, such as <code>Microsoft Windows Server 2012 R2 Base</code>,
<code>Microsoft Windows Server 2012 R2 with SQL Server Express</code>,
<code>Microsoft Windows Server 2012 R2 with SQL Server Standard</code>, or
<code>Microsoft Windows Server 2012 R2 with SQL Server Web</code>.
</p>
</li>
<li>
<p>
A custom AMI: <code>Custom</code>.
</p>
</li>
</ul>
<p>
Not all operating systems are supported with all versions of Chef. For more information about the supported
operating systems, see <a
href="https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-os.html">OpsWorks Stacks Operating
Systems</a>.
</p>
<p>
The default option is the current Amazon Linux version. If you set this parameter to <code>Custom</code>, you
must use the <a>CreateInstance</a> action's AmiId parameter to specify the custom AMI that you want to use. Block
device mappings are not supported if the value is <code>Custom</code>. For more information about how to use
custom AMIs with OpsWorks Stacks, see <a
href="https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-custom-ami.html">Using Custom
AMIs</a>.
</p>

@return The instance's operating system, which must be set to one of the following.</p>
        <ul>
        <li>
        <p>
        A supported Linux operating system: An Amazon Linux version, such as <code>Amazon Linux 2</code>,
        <code>Amazon Linux 2018.03</code>, <code>Amazon Linux 2017.09</code>, <code>Amazon Linux 2017.03</code>,
        <code>Amazon Linux 2016.09</code>, <code>Amazon Linux 2016.03</code>, <code>Amazon Linux 2015.09</code>,
        or <code>Amazon Linux 2015.03</code>.
        </p>
        </li>
        <li>
        <p>
        A supported Ubuntu operating system, such as <code>Ubuntu 18.04 LTS</code>, <code>Ubuntu 16.04 LTS</code>, <code>Ubuntu 14.04 LTS</code>, or <code>Ubuntu 12.04 LTS</code>.
        </p>
        </li>
        <li>
        <p>
        <code>CentOS Linux 7</code>
        </p>
        </li>
        <li>
        <p>
        <code>Red Hat Enterprise Linux 7</code>
        </p>
        </li>
        <li>
        <p>
        A supported Windows operating system, such as <code>Microsoft Windows Server 2012 R2 Base</code>,
        <code>Microsoft Windows Server 2012 R2 with SQL Server Express</code>,
        <code>Microsoft Windows Server 2012 R2 with SQL Server Standard</code>, or
        <code>Microsoft Windows Server 2012 R2 with SQL Server Web</code>.
        </p>
        </li>
        <li>
        <p>
        A custom AMI: <code>Custom</code>.
        </p>
        </li>
        </ul>
        <p>
        Not all operating systems are supported with all versions of Chef. For more information about the
        supported operating systems, see <a
        href="https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-os.html">OpsWorks Stacks
        Operating Systems</a>.
        </p>
        <p>
        The default option is the current Amazon Linux version. If you set this parameter to <code>Custom</code>,
        you must use the <a>CreateInstance</a> action's AmiId parameter to specify the custom AMI that you want
        to use. Block device mappings are not supported if the value is <code>Custom</code>. For more information
        about how to use custom AMIs with OpsWorks Stacks, see <a
        href="https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-custom-ami.html">Using
        Custom AMIs</a>.
aws-java-sdk-opsworks/src/main/java/com/amazonaws/services/opsworks/model/CreateInstanceRequest.java