Archive for July, 2008

Release Found: Red Hat® Enterprise Linux® 3, Update 4

Symptom:
After doing a complete update to Red Hat Enterprise Linux 3 Update 4, any further attempts to run up2date result in the following error:

# up2date --dry-run
Traceback (most recent call last):
  File "/usr/sbin/up2date", line 1174, in ?
    sys.exit(main() or 0)
  File "/usr/sbin/up2date", line 668, in main
    up2dateAuth.updateLoginInfo()
  File "up2dateAuth.py", line 151, in updateLoginInfo
  File "up2dateAuth.py", line 105, in login
  File "up2dateAuth.py", line 49, in maybeUpdateVersion
  File "/usr/share/rhn/up2date_client/up2dateUtils.py", line 228,
    in getVersion
    release, version = getOSVersionAndRelease()
  File "/usr/share/rhn/up2date_client/up2dateUtils.py", line 221,
    in getOSVersionAndRelease
    raise up2dateErrors.RpmError(
up2date_client.up2dateErrors.RpmError: RPM error.  The message was:
Could not determine what version of Red Hat Linux you are running.
If you get this error, try running

                rpm --rebuilddb

» Read more

In his entry XMLRPC vs REST vs SOAP vs CIM vs RMI vs Message Bus vs … Lots of RPC Options, Michael DeHaan opens his experience with RPC protocols and pours it out on the page.

This is based on not only a few apps like Cobbler and Func, but also past work where I’ve touched almost all of these first hand — I always seem to get stuck working on the backend server components wherever I go. This is by design — I like it there.

Michael then goes down a list of RPC protocols, noting positives (+) and negatives (-) about each based on his time working with remote procedure calling. He is the founder and lead developer for Cobbler, a next generation Linux provisioning server, and a Func hacker, a “secure (and) scriptable remote control framework and API.”

(Edited to clarify that Michael is a hacker in the Func collective, not a presumptive leader.)

What’s the word in open source news this week? Here’s the roundup.

• The Free Software Foundation listed a much-linked-to list of 5 reasons to avoid iPhone 3G, which led to articles like “Does open source have a new villain?” And along with a lot of customers, Lifehacker’s Gina Trapani sat on the fence between Freedom and iPhoneLove.
• First Radiohead joined the pay-what-you-wish club with the release of In Rainbows. Now they’re inviting you to play with their latest video.
• Event: OSCON is happening in Portland next week. Visit the Fedora booth.
• John Halamka, one of the keynote speakers at last month’s Red Hat Summit, wrote an interesting post about open source medical records.
• Not open source, but still interesting: Five ways technology will change the Beijing Olympics

Release Found: Red Hat Enterprise Linux 4 Update 2 and later

In order to setup device-mapper-multipathing an updated system with the package device-mapper-multipath is recommended.

This functionality does not exist in releases of Red Hat Enterprise Linux 4 prior to Update 2.

To set up device-mapper multipathing, edit the /etc/multipath.conf file. Comment out the following lines at the top of the file:

devnode_blacklist {
        devnode "*"
}

For example:

# devnode_blacklist {
#        devnode "*"
# }

» Read more

It’s been a good few weeks for stories and information about JBoss Rules and Drools, the open source project upstream of the JBoss subscription offering. Here is a quick summary of the recent stories. Post a comment if you know of any others we all should pay attention to.

• Pierre Fricke, JBoss product manager, writes about Daiwa Securities America Improves Performance and Reduces Costs with JBoss Enterprise Portal Platform. The Red Hat press release says, “In addition to the (JBoss) Portal Platform, Daiwa also uses the JBoss Rules framework to embed alerts into portal applications.”
• Two articles on Drools were published in Red Hat Magazine, Introduction to Drools: Rules fall from your eyes and JBoss Drools meets Hibernate. Both pieces are a good introduction to working with Drools.
• Drools continues to grow its library of widgets for the Guv’nor, which is the web tool and rules repository of Drools, formerly known just as the “Drools BRMS.” This new widget, rolodex, adds a flipping slideshow of photos pulled using Google Web Toolkit.
• A beta implementation of WordNet for Drools is being talked up by project lead Mark Proctor; they are seeking comments from users/testers in the Drools mailing list.
• Mark Proctor also writes, “We often get asked about Drools scalability in complex apps, so I thought I would link to this posting just done, where someone has Drools scaling to 900K facts on a 64bit JVM with reasonable performance.”
• More tools and features are being included in Drools all the time, such as adding Smooks as a data loader.

It is recommended that a resizing procedure be tested before performing it on a filesystem that contains critical data. It is also strongly recommended that data backups are created and verified before resizing filesystems. To assist the reader in becoming familiar with the resizing procedure, the rest of this article describes a scenario in which un-partitioned disk space is used to test logical volume and ext3 filesystem resizing.

In this test procedure, first we create a new partition (/dev/hda2) using un-partitioned disk space. A new volume group (TestVG) and logical volume (TestLV) are then created using a physical volume created on the partition. An ext3 filesystem is then created on the logical volume, it is checked, and then mounted. A new physical volume (/dev/hda3) using the rest of the un-partioned disk space is then created and added to the volume group and logical volume. Finally, the filesystem on the logical volume is resized, and the integrity of the filesystem is checked. » Read more

Remember Barton George? If you kept up with our Summit posts, then you’re familiar with Sun’s Linux guy, who was all over Boston blogging, podcasting, and interviewing. He’s back home now, but still putting together podcasts from his trip. Catch the two newest ones: Talking with Zmanda’s CEO, Chander Kant and Chattin’ with The Linux Foundation’s Executive Director, Jim “Led” Zemlin.

Also just in from the Red Hat News blog: One of our legal counsel penned a reader’s guide to the Firestar settlement. Totally worth reading if you’re at all interested in IP, licensing, and–in particular–the defensibility of the GPL.

The Red Hat Enterprise Linux 5 Installation Number is a 16-character hexadecimal text string used during the installation process. The installation number enables a user to install the full set of supported packages included with the subscription. For a limited set of Red Hat Enterprise Linux subscribers, the installation number is also used to activate subscriptions for additional Red Hat products and services. It replaces the Subscription Number from earlier versions of Red Hat Enterprise Linux.

Why use an installation number?

The Red Hat Enterprise Linux 5 installation trees and ISO images, in addition to the core operating system, contain a number of optional components. The Installation Number entered by the user during the installation process guides the Installer to include the correct components that match the user’s Red Hat Enterprise Linux Subscription. With certain types of Subscriptions it is also used to activate the Subscription in Red Hat Network. When registering the system to Red Hat Network (RHN), the Installation number is used to automatically subscribe the system to the right child channels. Finally it can be used by the customer to verify compliance to the subscription and might be requested by Red Hat Support when reporting an incident. » Read more

Jaroslaw is a JBoss QA Engineer based in Poland, and recently published an introduction to Drools that he kindly shared with us. This second piece covers Drools (or JBoss Rules), the open source business rules engine… in this case combining it with Hibernate.

This article is presented here in its entirety (with a trackback). The original can be found on Jaroslaw’s site. This article is also available in German and Polish.

Justification:

Drools evaluates facts which are present in the working memory. But could it also reason over data stored in a relational database? This feature would extend Drools’ range of applicability and since this is an often asked question in the mailing list, it’s worth to know the answer which sounds: “of course Drools can!”

Abstract:

Hibernate, one of the most favorite ORM tools, allows to handle data stored in a relational database. This article will describe how one can access a Hibernate session from inside the rule engine. I will use PostgreSQL as a data source. Besides that I will create two classes, Game and Player, having a many-to-many relationship. » Read more

One of our long-time writers introduced us to Jaroslaw, a JBoss QA Engineer based in Poland, and mentioned that he’d been working on some documentation we might find interesting. And, boy, do we! This first piece de-mystifies the complex world of rules engines. Whether you call it Drools, or JBoss Rules, or JBoss Drools… you still might want to know what it does and how it functions in your technical environment. (Not to mention that it’s just all kinds of logical and interesting–if you like brainteaser word puzzles or abstract math questions, this qualifies as pleasure reading.)

This article is presented here in its entirety (with a trackback). The original can be found on Jaroslaw’s site. This article is also available in German and Polish.

Justification:

Either you’re a developer, architect or a business analyst, it’s worth to get familiar at least with the first chapter of this article. It contains an introduction into the world of rule engines, which increase the readability of certain applications and make them easier to manage and to maintain. It applies to apps that take decisions, which depend on events or a state of some objects.

Abstract:

This article contains an introduction to rule engines, a description of an installation of Eclipse IDE and a guide how to configure Eclipse with the Drools Workbench plug-in. » Read more