Installation guide

Chapter 1. Introduction 3
Red Hat Update Agent — The Red Hat Update Agent is the Red Hat Network client application
(up2date) that allows users to retrieve and install new or updated packages for the client system
on which the application is run.
•
Traceback — A traceback is a detailed description of "what went wrong" that is useful for trou-
bleshooting the RHN Proxy Server. Tracebacks are automatically generated when a critical error
occurs and are mailed to the individual(s) designated in the RHN Proxy Server’s configuration file.
For more detailed explanations of these terms and others, refer to the Red Hat Network Reference
Guide available at http://www.redhat.com/docs/.
1.4. How it Works
The Red Hat Update Agent on the client systems does not directly contact a Red Hat Network Server.
Instead, the client (or clients) connects to an RHN Proxy Server that connects to the Red Hat Network
Servers or to a RHN Satellite Server. Thus, the client systems do not need direct access to the Internet.
They need access only to the RHN Proxy Server.
Important
Red Hat strongly recommends that clients connected to RHN Proxy Server be running the latest
update of Red Hat Enterprise Linux to ensure proper connectivity.
By default, a client is authenticated directly by Red Hat Network Servers. Using an RHN Proxy Server,
authentication works similarly except that the RHN Proxy Server provides route information as well.
After a successful authentication, the Red Hat Network Server informs the RHN Proxy Server that it
is permitted to execute a specific action for the client. The RHN Proxy Server downloads all of the
updated packages (if they are not already present in its cache) and delivers them to the client system.
Requests from the Red Hat Update Agent on the client systems are still authenticated on the server
side, but package delivery is significantly faster since the packages are cached in the HTTP Proxy
Caching Server or the RHN Proxy Server (for local packages); the RHN Proxy Server and client
system are connected via the LAN and are limited only by the speed of the local network.
Authentication is done in the following order:
1. The client performs a login action at the beginning of a client session. This login is passed
through one or more RHN Proxy Servers until it reaches a Red Hat Network Server.
2. The Red Hat Network Server attempts to authenticate the client. If authentication is successful,
the server then passes back a session token via the chain of RHN Proxy Servers. This token,
which has a signature and expiration, contains user information, including subscribe-to chan-
nels, username, etc.
3. Each RHN Proxy Server caches this token on its local file system in /var/cache/rhn/.
Caching reduces some of the overhead of authenticating with Red Hat Network Servers and
greatly improves the performance of Red Hat Network.
4. This session token is passed back to the client machine and is used in subsequent actions on Red
Hat Network.
From the client’s point of view, there is no difference between an RHN Proxy Server and a Red
Hat Network Server. From the Red Hat Network Server’s point of view, an RHN Proxy Server is a
special type of RHN client. Clients are thus not affected by the route a request takes to reach a Red