Wednesday Apr 17, 2013

How the Oracle Linux Update Channels are Structured

Beer Taps by Jamie C2009, on Flickr
"Beer Taps" by Jamie C2009 (CC BY 2.0).

Oracle Linux distribution releases are identified by a major version like "Oracle Linux 6" or "Oracle Linux 5", followed by an update release number, e.g. "Oracle Linux 6 Update 3" or "Oracle Linux 6.3" in short. Every Oracle Linux distribution release is freely available as ISO installation images from the Oracle Software Delivery Cloud (formerly known as E-Delivery), as well as individual RPM packages, broken up by update releases. These are published via "channels" (or "yum repositories") from the Unbreakable Linux Network (ULN) and our public yum repository

Security patches and critical bug fixes (errata) for individual packages that are being released in between update releases are published immediately via the corresponding _latest yum repositories and ULN channels at the same time. If you want to ensure that your system is always up to date and fully patched, make sure to have it subscribed to the _latest channel (e.g. ol6_latest). And you don't even need to purchase a support subscription for that, if you use the public yum repositories!

Update releases of a major distribution version are primarily "checkpoints", an accumulation of all patches that have been published since the last update release has been made available. They help to reduce lengthy patch/update procedures that would have to be performed if you would always have to start a new installation from the very first release of a new major version. Update releases within a major version are binary compatible. An application that was installed and tested on Oracle Linux 6.1 will still run on Oracle Linux 6.4.

In addition to the _latest channel, ULN also provides so-called _patch channels, one per update release (e.g. ol6_u4_x86_64_patch for Oracle Linux 6.4 on x86_64). These _patch channels contain all RPM updates that have been published after a new update release (e.g. 6.4) has been released. They are kept up to date with each new update package that is made available. So they allow you to keep a certain update level of the distribution up to date without risking rolling forward to a new update release version automatically (which is what happens when your system is subscribed to the _latest repository).

However, one thing to keep in mind is that these channels actually stop receiving updates once a new update release (e.g. 6.4) has been made available. At this point you need to "go with the flow" and plan your update to the next update release (and its associated _patch channel), if you don't want to risk running an un-patched system.

I'd like to give you an alternative explanation of this channel structure, using software development and source code version control as an analogy. In revision control terms, you could consider the _latest channel the "trunk" of the distribution, a stream of packages that is always up to date and also rolls forward the distribution's update version in regular intervals. The _base channels could be considered "tags" or "snapshots" of the _latest package stream. They represent the state of a major distribution version (e.g. Oracle Linux 6) at a certain point in time, identified by a minor version number (e.g. 6.3). They are being packaged and released in the form of an ISO image as well. The _patch channels could be considered "branches" that are branched off a certain tag and are being kept up to date with the "trunk" until a new update release has been tagged.

I hope this explanation helps understanding the various channels and their purposes!

- Lenz Grimmer

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Wednesday Jun 15, 2011

Pimp my Ride - Installing Additional Packages on Oracle Linux

Lee Cannon: Wings Wheels 2010
"Wings Wheels 2010" by Lee Cannon (CC BY-SA 2.0).

Oracle Linux already ships with an impressive amount of software packages which can be downloaded from our public Yum server.

For example, adding the external package repository for Oracle Linux 6.1 is a trivial task:

  1. Download and copy the appropriate yum configuration file in place, by running the following command as root:
    # wget -O /etc/yum.repos.d/public-yum-ol6.repo \
      http://public-yum.oracle.com/public-yum-ol6.repo
  2. Now edit the file using your favorite text editor and enable the appropriate repository ([ol6_u1_base] in our case) by changing the value of the enabled variable from 0 to 1.
  3. Now you can run yum list all to get a full list of all available packages. You can install them by running yum install <packagename>
However, being a distribution with a focus on the enterprise and data center, the package selection is limited to this scope. If you are looking for additional packages, you would have to either compile them from source or download pre-built binaries from an external package repository.

Enter EPEL, the "Extra Packages for Enterprise Linux" repository. According to their extensive FAQ, EPEL "is a volunteer-based community effort from the Fedora project to create a repository of high-quality add-on packages that complement the Fedora-based Red Hat Enterprise Linux (RHEL) and its compatible spinoffs, such as CentOS and Scientific Linux.".

Oracle Linux is based on RHEL, too, and is 100% userland-compatible with it. Therefore any package available from EPEL will install and run just fine, giving you access to a large pool of additional software. However, please keep in mind that this software is not covered by any Oracle Linux Support agreement you may have!

You can add and enable the EPEL repository by performing the following steps (as the root user):

  1. Download and install the repository package which includes the appropriate repository information for your version of Oracle Linux:
    rpm -Uvh http://download.fedora.redhat.com/pub/epel/6/x86_64/epel-release-6-5.noarch.rpm
  2. The repository is automatically enabled, which you can verify by running yum repolist.
  3. To get a listing of all the additional packages you now have access to, run yum list available | grep epel | less.
  4. Now simply run yum install <packagename> to install any of the additional packages (over 4800 for Oracle Linux 6, last time I counted!).
Enjoy!

See more articles about Oracle Linux at the Oracle Linux Blog!

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