Chapter 1. About Red Hat Update Infrastructure 4

The following figure depicts a high-level view of how the various Red Hat Update Infrastructure 4 components interact.

Figure 1.1. Red Hat Update Infrastructure 4 overview

Install the RHUA and CDS nodes on separate x86_64 servers (bare metal or virtual machines). Ensure all the servers and networks that connect to RHUI can access the Red Hat Subscription Management service.

There is one RHUA per RHUI installation, though in many cloud environments there will be one RHUI installation per region or data center, for example, Amazon’s EC2 cloud comprises several regions. In every region, there is a separate RHUI set up with its own RHUA node.

The RHUA allows you to perform the following tasks:

RHUI uses two main configuration files: /etc/rhui/rhui-tools.conf and /etc/rhui/rhui-subscription-sync.conf.

The /etc/rhui/rhui-tools.conf configuration file contains general options used by the RHUA, such as the default file locations for certificates, and default configuration parameters for the Red Hat CDN synchronization. This file normally does not require editing.

The Red Hat Update Infrastructure Management Tool generates the /etc/rhui/rhui-subscription-sync.conf configuration file based on user-inputted values. It contains all the information that drives the running of a RHUA in a particular region. An example configuration includes the destination on the RHUA to download packages.

The RHUA employs several services to synchronize, organize, and distribute content for easy delivery.

The CDS nodes provide the repositories that clients connect to for the updated content. There can be as few as one CDS. Because RHUI provides a load-balancer with failover capabilities, we recommended that you use multiple CDS nodes.

The CDS nodes host content to end-user RHEL systems. While there is no required number of systems, the CDS works in a round-robin style load-balanced fashion (A, B, C, A, B, C) to deliver content to end-user systems. The CDS uses HTTP to host content to end-user systems via httpd-based yum repositories.

During configuration, you specify the CDS directory where packages are synchronized. Similar to the RHUA, the only requirement is that you mount the directory on the CDS. It is up to the cloud provider to determine the best course of action when allocating the necessary devices. The Red Hat Update Infrastructure Management Tool configuration RPM linked the package directory with the NGINX configuration to serve it.

Currently, RHUI supports the following shared storage solutions:

If these default values are used, the /export directory on the RHUA and the /var/lib/rhui/remote_share directory on each CDS are identical.

The expected usage is that you use one shared network file system on the RHUA and all CDS nodes, for example, NFS. It is possible the cloud provider will use some form of shared storage that the RHUA writes packages to and each CDS reads from.

The only nonstandard logic that takes place on each CDS is the entitlement certificate checking. This checking ensures that the client making requests on the yum repositories is authorized by the cloud provider to access those repositories. The check ensures the following conditions:

If the CA verification fails, the client sees an SSL error. See the CDS node’s NGINX logs under /var/log/nginx/ for more information.

[root@cds01 ~]# ls -1 /var/log/nginx/
access.log
error.log
gunicorn-auth.log
gunicorn-content_manager.log
gunicorn-mirror.log
ssl-access.log----

If more than one CDS is used, a load-balancing solution must be in place to spread client HTTPS requests across all servers. RHUI ships with HAProxy, but it is up to you to choose what load-balancing solution (for example, the one from the cloud provider) to use during the installation. If HAProxy is used, you must also decide how many nodes to bring in.

Clients are not configured to go directly to a CDS; their repository files are configured to point to HAProxy, the RHUI load-balancer. HAProxy is a TCP/HTTP reverse proxy particularly suited for high-availability environments. HAProxy performs the following tasks:

The exact configuration depends on the particular load-balancer software you use. See the following configuration, taken from a typical HAProxy setup, to understand how you should configure your load-balancer:

[root@rhui4proxy ~]# cat /etc/haproxy/haproxy.cfg
# This file managed by Puppet
global
  chroot  /var/lib/haproxy
  daemon
  group  haproxy
  log  10.10.153.149 local0
  maxconn  4000
  pidfile  /run/haproxy.pid
  stats  socket /var/lib/haproxy/stats
  user  haproxy

defaults
  log  global
  maxconn  8000
  option  redispatch
  retries  3
  stats  enable
  timeout  http-request 10s
  timeout  queue 1m
  timeout  connect 10s
  timeout  client 1m
  timeout  server 1m
  timeout  check 10s

listen https00
  bind 10.10.153.149:443
  balance roundrobin
  option tcplog
  option tcp-check
    server cds01.example.com cds01.example.com:443 check
    server cds02.example.com cds02.example.com:443 check

Keep in mind that when clients fail to connect, it is important to review the nginx logs on the CDS under /var/log/nginx/ to ensure that any request reached the CDS. If requests do not reach the CDS, issues such as DNS or general network connectivity may be at fault.

A repository is a storage location for software packages (RPMs). RHEL uses yum commands to search a repository, download, install, and configure the RPMs. The RPMs contain all the dependencies needed to run an application. RPMs also download updates for software in your repositories.

RHEL uses core technologies such as control groups (cgroups) for resource management, namespaces for process isolation, and SELinux for security, enabling secure multiple tenancy, and reducing the potential for security exploits. These technologies enable rapid application deployment, simpler testing, maintenance, and troubleshooting while improving security.

Content, as it relates to RHUI, is the software (such as RPMs) that you download from the Red Hat CDN for use on the RHUA and the CDS nodes. The RPMs provide the files necessary to run specific applications and tools. Clients are granted access by a set of SSL content certificates and keys provided by an rpm package, which also provides a set of generated yum repository files.