Introduction

This project contains the build-automation for creating LVM-enabled Enterprise Linux 9 AMIs for use in AWS envrionments. Testing and support will be given to RHEL 9 and CentOS 9-stream. Other EL9-derivatives should also work. However, there are currently no plans by the project-owners to specifically verify compatibility with other RHEL9-adjacent distributions.

Purpose

The DISA STIGs specify that root/operating-system drive must have a specific, minimum set of partitions present. Because re-partitioning the root drive is not practical once a system – particularly one that is cloud-hosted – is booted, this project was undertaken to ensure that VM templates (primarily Amazon Machine Images) would be available to create virtual machines (primarily EC2s) that would have the STIG-mandated partitioning-scheme "from birth".

As of the RHEL 9 v1r1 STIG release, the following minimum set of partitions are required:

• /home (per: V-257843/RHEL-09-231010)
• /tmp (per: V-257844/RHEL-09-231015)
• /var (per: V-257845/RHEL-09-231020)
• /var/log (per: V-257846RHEL-09-231025)
• /var/log/audit (per: V-257847/RHEL-09-231030)
• /var/tmp (per: V-257848 /RHEL-09-231035)

The images published by this project owner to AWS – in the commercial and GovCloud partitions – have a filesystem layout that looks like:

# df -PH
Filesystem                    Size  Used Avail Use% Mounted on
devtmpfs                      4.2M     0  4.2M   0% /dev
tmpfs                         4.1G     0  4.1G   0% /dev/shm
tmpfs                         1.7G  9.0M  1.7G   1% /run
/dev/mapper/RootVG-rootVol    4.3G  1.7G  2.7G  38% /
tmpfs                         4.1G     0  4.1G   0% /tmp
/dev/mapper/RootVG-homeVol    1.1G   42M  1.1G   4% /home
/dev/nvme0n1p3                508M  231M  277M  46% /boot
/dev/mapper/RootVG-varVol     2.2G  232M  2.0G  11% /var
/dev/nvme0n1p2                256M  7.4M  249M   3% /boot/efi
/dev/mapper/RootVG-logVol     2.2G   68M  2.1G   4% /var/log
/dev/mapper/RootVG-varTmpVol  2.2G   50M  2.1G   3% /var/tmp
/dev/mapper/RootVG-auditVol   6.8G   82M  6.7G   2% /var/log/audit
tmpfs                         819M     0  819M   0% /run/user/1000

Users of this automation can customize both which partitions to make on the root disk as well as what size and filesystem-type to make them. Consult the DiskSetup.sh utility's help pages for guidance.

Further Security Notes

Additionally, the system-images produced by this automation allows the following system-security features to be enabled:

• FIPS 140-2 mode
• SELinux – set to either Enforcing (preferred) or Permissive
• UEFI support (to support system-owner's further ability to enable SecureBoot and other Trusted-Computing capabilities)

This capability is offered as some organizations' security-auditors not only require that some or all of these features be enabled, but that they be enabled "from birth" (i.e., a configuraton-reboot to activate them is not sufficient).

As of the writing of this guide:

• FIPS mode is enabled (verify with fips-mode-setup --check)
• SELinux is set to Enforcing (verify with getenforce)
• UEFI is available (verify with echo $( [[ -d /sys/firmware/efi/ ]] )$? or dmesg | grep -i EFI)

Lastly, host-based firewall capabilities are enabled via the firewalld service. The images published by this project's owners only enable two services: sshd and dhcpv6-client. All other services and ports are blocked by default. These settings may be validated using firewall-cmd --list-all.

Software Loadout and Updates

The Red Hat images published by this project's owners make use of the @core RPM package-group plus select utilities to cloud-enable the resulting images (e.g. cloud-init and CSP-tooling like Amazon's SSM Agent and AWS CLI).

The Red Hat images published by this project's owners make use of the official Red Hat repositories managed by Red Hat on behalf of the CSP. If these repositories will not be suitable to the image-user, it will be necessary for the image-user to create their own images. The OSpackages.sh script accepts arguments that allow the configuration of custom repositories and RPMs (the script requires custom repositories be configured by site repository-RPMs)

CSP Enablement

The image build-automation also includes the option to bake in CSP-specific tooling.

Note: As of this writing, the only CSP-enablement included in this project has been for AWS. If enablement for other CSPs is desired, it is recommended that users of this project contribute suitable automation and documentation.

AWS Enablement

AWS-enablement is provided through the AWSutils.sh script. This script can install:

• AWS CLI v2: See the AWS CLI Getting Started page for default, AWS-managed locations for the AWS CLI v2 installers
• AWS CloudFormation bootstrapper (cfn-bootstrap): See "CloudFormation helper scripts reference" for default, AWS-managed locations for the cfn-bootstrap Python modules
• AWS SSM Agent: See the AWS Systems Manager document's Quick Installation Commands section for default, AWS-managed locations for the Amazon SSM Agent RPM

This scriipt can also enable arbitrary systemd services. Typically, this will just be the amazon-ssm-agent service.

Invoke the ./AWSutils.sh with either the -h or --help for the list of flags necessary to specify the above installation-options.