## 2011-08-01

### Review: CentOS 6.0

 Main Screen
Red Hat Enterprise Linux (RHEL) 6.0 was released a little less than 9 months ago, while RHEL derivative Scientific Linux 6.0 "Carbon" was released a little less than 5 months ago. Yet, it took 8 months after the release of RHEL 6.0 for CentOS 6.0 to be released. Two weeks after that, the CentOS 6.0 live medium was released, so I'm trying it out and reviewing it now.

So what is CentOS? Well, before I say that, it's important to know that RHEL is the flagship product of Red Hat; it's an OS meant for business and server environments, and its price is almost entirely for technical support, which can be purchased at different levels. It isn't available for home users for free; that's where Fedora and CentOS come in. Fedora is basically like RHEL's upstream, in that every few Fedora releases, a new version of RHEL based on that Fedora version is released; for example, Fedora Core 6 formed the basis of RHEL 5, while a combination of Fedora 12 and 13 formed the basis of RHEL 6. CentOS, on the other hand, is RHEL's clone; it is 100% identical to RHEL, except that all Red Hat branding is replaced by CentOS branding, and all references to Red Hat and RHEL are replaced by references to a more generic "upstream" or "Enterprise Linux", due to Red Hat's policies regarding its logo and name. Replacing the branding and rebuilding the packages is not trivial, and as far as I can tell, this release was particularly problematic, which is why it took a full 8 months (as opposed to the typical 1-3 months) after the corresponding RHEL release for the new CentOS version to be released.
Unfortunately, this unprecedented delay irritated some of the more vocal members of the Linux community, and as Scientific Linux 6.0 "Carbon" was released many months before CentOS 6.0 (while typically the newest Scientific Linux version is released after the corresponding CentOS version), former users of CentOS started switching to Scientific Linux. Well, CentOS 6.0 is finally here, so hopefully those disgruntled users are happy.

I tested CentOS on a live USB made with MultiSystem. I did not test the installation because I did that with Scientific Linux, and I don't see any reason why the installation should be any different; this is the same reason why I don't test the installation for every Ubuntu derivative I try out. Follow the jump to see what it's like. Also note that I originally wanted to do a direct comparison between Scientific Linux and CentOS, but I got impatient in waiting for the CentOS 6.0 live CD to be released, so I went ahead and tested Scientific Linux 6.0 "Carbon" by itself. Therefore, this article will make frequent references and comparisons to Scientific Linux. Finally, as was the case with the Scientific Linux review, though CentOS is really targeted at enterprise users and servers, I'm going to be reviewing it from the perspective of a home desktop user. Why? Well, Microsoft Windows 2000, the first home version of Microsoft Windows to be based on Microsoft Windows NT, which was previously just for servers and enterprise users, was very well-received among home users despite it targeting enterprise and server use. I'm reviewing CentOS from that same perspective.

After rebooting and getting past the boot menu, I was greeted by a scrolling wall of text. While this wasn't bad per se, it would have been nice to see a boot splash like Scientific Linux. A short while after that, I was taken to the GDM screen, where I was eventually logged in automatically. That took me to the GNOME 2.28 desktop, which was identical to that of Scientific Linux, save for the replacement of the logo with that of CentOS. There really isn't much else for me to report there, so I won't dwell on it further.

 Mozilla Firefox + GNOME Terminal
As in Scientific Linux, Mozilla Firefox 3.6 is the default browser in CentOS. Unlike Scientific Linux, CentOS did not have multimedia codecs included, as I was unable to watch YouTube and Hulu. I found and followed some simple instructions to use the terminal to get Adobe Flash and other codecs, and that worked and happened quickly. After that, I was able to watch YouTube and Hulu fine; furthermore, CentOS properly recognized my laptop's sound card and volume keyboard shortcuts out-of-the-box, which was good.

The default application selection, otherwise identical to that of Scientific Linux, was fairly sparse, so I went to the package manager PackageKit to get some software; I decided to install OpenOffice.org (unfortunately, CentOS isn't quite new enough to have LibreOffice available in the repositories by default). That took a little time to happen, but afterwards, I got a nice dialog box asking me if I wanted to run any of the installed programs; it could use a little work, because it offered to run secondary nonexecutable packages, but it was still a nice touch.

After this, I decided to install Skype and the Google Talk browser plugin. Getting, installing, and using both RPM packages was, as in Scientific Linux, a cinch; both recognized my webcam and mic properly out-of-the-box. It was just a matter of downloading the RPMs from the respective websites and opening them with the package installers as suggested by Mozilla Firefox.

 Nautilus + PackageKit
Nautilus behaves the same in CentOS as in Scientific Linux, in that when a shortcut on the desktop or in the "Places" menu is clicked, it opens that folder in spatial mode, whereas if the "File Browser" is opened from the "Applications" menu, it opens to the home folder in browser mode. I think I know why this is: when the shortcut is clicked, it's only supposed to show the contents of that folder, but when "File Browser" is clicked, it should be able to browse the contents of any folder. That said, I still feel that this is inconsistent behavior, and while I would definitely prefer that Nautilus open in browser mode everywhere, I would at least like to see consistency.

Desktop effects weren't even present in CentOS; I mean, there wasn't even the small dialog to enable the desktop cube or the wobbly windows. That window is present in both Fedora and Scientific Linux, so I found its absence from CentOS strange. Of course, it is available in the package manager, but I suppose CentOS is really trying to push itself as a no-nonsense enterprise OS.
CentOS never once felt slow or sluggish, and the numbers bore that assertion out; at idle, CentOS used just 220 MB of RAM, while with Mozilla Firefox open with 11 tabs open, CentOS used just 370 MB of RAM.
I tried suspending the laptop in CentOS, but it didn't work. Once again, I won't blame CentOS, but this time I have a little more insight as to why it didn't work: for suspending to work, it needed to read a certain file present in the desktop folder,  and for whatever reason, that file didn't exist in the live session, so the suspending process got hung up there, so I needed to force a cold reboot. Anyway, that's where my time with CentOS ended.

So what's the deal? CentOS is outwardly identical to Scientific Linux except for four things: branding, lack of boot splash, lack of multimedia codecs included out-of-the-box, and lack of compositing/desktop effects out-of-the-box. The first of course is not an issue at all, while the second, third, and fourth are minor issues than can be fixed easily. However, I've also discussed the differences between CentOS and Scientific Linux with a friend ($friend) who is much more knowledgeable about these things than myself, and$friend said that while CentOS simply changes the branding of all RHEL packages, thus ensuring 100% compatibility with RHEL, Scientific Linux seems to completely reverse-engineer all RHEL packages. This means that while compatibility with RHEL is possible 99% of the time, it isn't fully guaranteed like it is with CentOS; furthermore, somehow the scientific packages (which Scientific Linux is supposed to be known for) get messed up, which means that scientific software ironically works better in CentOS than in Scientific Linux. Thus, if you are truly concerned about 100% compatibility with RHEL and being able to take advantage of exactly the same updates as RHEL, use CentOS. Otherwise, while I can recommend CentOS for newbies who want a rock-solid stable OS with 10 years of support and no gimmicks, I see no reason to use it over Scientific Linux, which has all those same nice features plus a few extra goodies to make it more palatable for home users.
You can get CentOS here.