RHEL as a Desktop

A GUI is often considered secondary in enterprise systems, because these systems primarily end up on servers. Although the distributors no longer have enterprise desktops (like the one SUSE temporarily had in its portfolio), many companies still install RHEL and its competitors on desktops to ensure a certain continuity in the employees' workplaces.

This explains why RHEL 7 comes with three different desktops. In the standard configuration, Gnome classic is used, which strongly resembles Gnome 2 in terms of look and feel. Alternatively, KDE4 and Gnome 3 are available with the Gnome shell. Most of the typical desktop tools already look prehistoric: Firefox 24 is unlikely to impress anyone; the count had already progressed to number 30 on the desktop of our lab machine.

An office suite such as Libre or OpenOffice is missing and needs to be installed manually. Additionally, the ancient 3.10 kernel that RHEL uses will soon lack support for current desktop hardware. Again, you can easily see that Red Hat is primarily targeting servers with RHEL. A Fedora installation is advisable anyway for everyday use, even if you can add new features to the old kernel via backports.

High-Availability Drama

At the very end of the RHEL 7 changelog, you'll find some remarks on the topic of high availability. It almost looks as if the manufacturer did not want to advertise this feature, although RHEL 7 has changed more in terms of high availability than it has for several major RHEL versions. As of RHEL 7, Red Hat joins the Pacemaker camp as the last manufacturer to adopt the de facto standard for cluster management on Linux.

Although SUSE has invested a large sum in promoting the development of Heartbeat 1 and 2 in the past 15 years, Red Hat preferred to go its own way: Red Hat carved an HA solution from the Piranha backup software that was later renamed Red Hat Cluster Suite (RHCS) [11]. When many companies agreed on a common standard for cluster communication in the scope of the Service Availability Forum (SAF), even the red hats had to join the group.

Red Hat developers wrote the first FLOSS implementation of AIS, the application interface specification. Novell picked up the ball at the time and instructed its own developer, Andrew Beekhof, to rebuild Heartbeat 2 so that it worked with what was then called the openAIS suite. Pacemaker was born [12].

Red Hat would not be Red Hat if it had not found a unique way to integrate Pacemaker. Corosync [13], as a successor to open AIS and Pacemaker, works perfectly in this combination. Red Hat decided, however, to recycle cman from the RHCS and add Pacemaker as its sidekick. If you have already successfully built a Pacemaker setup on other distributions, you need to relearn for Red Hat.

This is also true of modifying the cluster configuration. Pacemaker still internally uses an XML file that contains all the resources. SUSE contributed a tool for editing the XML file via plain text files years ago, crmsh [14], which translates between text and XML formats.

However, Red Hat did not want the CRM shell and began to work on PCS, which is the standard tool for cluster configuration in RHEL 7. Most tutorials on the net, however, still refer to the CRM shell, which is clearly superior to PCS in terms of its feature set. If you use RHEL 7 to implement high availability, you get Pacemaker, but in a flavor that tastes like Red Hat (Figure 6).

Figure 6: RHEL 7 is the first version of RHEL to come with Pacemaker – a Red Hat-style Pacemaker.

Conclusions

Red Hat Enterprise Linux 7 is a solid upgrade that will not disappoint the expectations of passionate Red Hat admins. Some innovations are really smart; the performance profiles offer up to 40 percent speed advantage over older versions of RHEL, according to the advertising blurb from the Red Hat marketing department.

The core of the operating system, Linux 3.10, is a typical Frankenstein kernel – as usual for enterprise systems  – that has been dragged kicking and screaming over a huge pile of patches to support the current state of the art, Linux 3.15. If you were thinking of installing RHEL 6, there is no reason not to go straight for RHEL 7. Whether or not the features warrant a dedicated update can only be clarified by individual analysis. In my case, however, there is no urgent, across-the-board reason to update RHEL 6 to the new version.