## 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.

#### 26 comments:

1. CentOS really is NOT a desktop version of RHEL as you say. It is NOT really comparable to Fedora. Instead it is a "free as in money" version of RHEL (full stop). It is really meant to be an Enterprise class server OS that "can be used" as a desktop version, but usually by those using it on their servers.

2. The Live DVD of CentOS 6 has the special effects you were craving plus many many more applications including kde ones. On my Thinkpad T61 it runs perfectly and is very stable with support to 2016 and beyond.

3. I also tried CentOS 6.0 and was amazed. It is so much different (positively) from CentOS 5.x!

4. Except for a few nits, CentOS6 and Scientific Linux 6 should be identical. They have been in my testing (for server use). Why anyone would choose CentOS over SL after the repeated delays in updates (for both versions 5 and 6) in the last couple of years is a complete mystery to me. Scientific Linux is also free, is updated more frequently, and is supported by CERN and Fermi National Lab. No contest.

5. Can you explain what you mean by the statement that "Scientific Linux seems to completely reverse-engineer all RHEL packages"? I was under the impression the SL team did pretty much the same as the CentOS team while adding some extras - strip out the branding in other words and add a few fonts and a lightweight window manager. Nowhere else have I come across the assertion that the SL crew completely reverse-engineer all RH packages.

6. I hate to say bad things about your friend, but he's wrong about SL "reverse-engineer"ing the RHEL packages.
Unless a package has to be changed for branding reasons, we make no change whatsoever to our RHEL's source rpm's. We don't even unpack them.
I should know, I'm the person who does it.

7. Not to be the bearer of bad news, but the world ENDS on December 21st, 2012. So this and all other distros have until then to be supported.

8. pv and other readers, what free distro do you guys use to run cadence (if rhel is not an option)?

9. @Anonymous 1: I never said it was a desktop version of RHEL. In fact, I said most of what you said, which is that Fedora is like the desktop version of RHEL, while CentOS is the free clone of RHEL and is really meant for enterprise use; the only thing is there is that here, I'm personally reviewing its abilities as a home desktop distribution. You may want to read the first few paragraphs of the review again.
@MIchael J King: I appreciate the clarification, and I do realize that standard support lasts for 6 years (with extended support for an additional 3, which all in all makes for an effective 9-10 years of support as I said, unless CentOS doesn't get the same extended support as RHEL), but I still don't understand why if Scientific Linux could include such goodies in the *live CD*, why CentOS couldn't do the same in its *live CD*.
@DarkDuck: I read your review, and it was certainly interesting. I've never tried CentOS 5.X; in fact, this is my first time trying CentOS, so for me, my only comparisons are Scientific Linux, Fedora, and Fedora derivatives.
@Anonymous 2: I thought CentOS was pretty good about keeping up with RHEL for version 5 while Scientific Linux came out a little later for that release, but there's no question that the delay for version 6 has angered a lot of CentOS users and has at the same time helped the Scientific Linux community as that distribution's release was slightly more timely.
@Gerard Lally: If I remember what $friend said correctly, basically, the CentOS developers just unpack packages, rebrand them, and then repack them, but the Scientific Linux developers build all the RPMs from scratch for some reason. I don't know how true this is, but I can only assume$friend is telling the truth because $friend does heavily use RHEL, CentOS, and Fedora, and even develops packages for Fedora and CentOS in spare time. @Troy Dawson: I greatly appreciate the clarification. That basically negates my previous comment then. Hehheh. I'm going to be having a chat with$friend pretty soon then....
@Joy Ro: I can't tell if you're trolling or if you're trying to be humorous, but in any case, huh?
@somethingquarky: I'm not entirely sure what Cadence is. Could other commenters please enlighten us on this?
Thanks for the comments!

10. @[all]: I just talked with $friend, and$friend confirmed that Scientific Linux does indeed do the same thing as CentOS for basic packages ($friend wasn't clear with me on this before), but not for scientific packages, though I'd appreciate it if someone could check up on that and let me know. Also,$friend admits having never tried Scientific Linux before (exclusively using RHEL, Fedora, and CentOS) and that Scientific Linux 6.0 may be better than \$friend previously thought. Once again, thanks for the comments!

11. CentOS has better hardware support than Scientific Linux. On my desktop computer, CentOS has sound but SL does not, because my sound chip is unsupported by Red Hat.

Incidentally, it is incorrect to say RHEL is only a server distro: if you go to their products listing, you'll find separate listings for the server and desktop versions.

12. @Anonymous: That's interesting that Scientific Linux doesn't support the sound card, but CentOS does. Also, I didn't [mean to] say that RHEL is only for servers; I also said it was for enterprise use (though I should have specifically said enterprise *desktop* use, to be totally clear). Thanks for the comment!

13. I like centos 6 64bit alot it's more stable then mint, but cant figure out why there is som many KDE in cento when using gnome deleting KDE isnøt so good because you need alot of the KDE stuff

14. I like centos 6 64bit alot it's more stable then mint, but cant figure out why there is som many KDE things in centos when using gnome deleting KDE isn't so good because you need alot of the KDE stuff.

Having trouble with updates that i cant instal, hope i can get it fixed------------

15. @Michael: It's great that you're finding it to be so stable, but I'm confused — is there too much KDE stuff in CentOS or not enough? Thanks for the comment!

16. I've used CentOS for about three years. I think your review was pretty accurate, except the bit about Scientific Linux being reverse engineered. SL and CentOS are almost the same, except the SL team is less shy about adding a few applications and doing some of their own customisations. And, originally at least, the two distributions were aimed at different "markets." CentOS is a RHEL clone, intended for the Enterprise, and Scientific Linux was created by government agencies (CERN and Fermi Lab) who wanted a solid OS for their work.

I do want to make one comment about release dates -- and you already partially mentioned this -- but it should be noted that RHEL 4.9, 5.6 and 6.0 all came out close to the same time. Scientific Linux, since they release updates between releases, held off on getting 5.6 and 4.9 done while they worked on 6.0. CentOS went the opposite direction. They released 4.9, 5.6, then 6.0. So, if you put all three releases together, and take into account the overall finishing dates for the three releases together, the time was about the same -- just in a different order. Before 6.0, CentOS almost always came out just a bit before SL. For some reason there seems to be a bit of historical revisionism going on here -- with the claim being made that SL was always out faster.

17. @Rob Centros: If you noticed a little bit above your comments, I retracted that statement about Scientific Linux reverse engineering RPM packages (which was actually a statement made by one of my friends who uses RHEL/CentOS/Fedora regularly but has never used Scientific Linux). Also, you make a very good point about the release dates. It's definitely something worth noting and shows that CentOS could be more committed to releasing stable products when ready as opposed to new products as soon as possible, but it seems like enough people were impatient with CentOS to move to Scientific Linux due to the release date disparities. Thanks for the comment!

18. Interesting article. From my perspective, I use Centos 6 because it seems more adaptable to my Virtual Box installation. I never did figure out the proper way to add Guest Additions and USB extensions in Scientific but it took me less than 5 minutes to install it in Centos. Maybe Centos just has a better community but after 20 minutes I gave up on SL.

19. I swear I'm not trying to troll, but your review doesn't really provide much insight into CentOS (or other operating systems for that matter). Much of the appeal in running RHEL and CentOS is in the server management, security, and stability. Running Firefox, displaying Flash, or installing word processors are not really insightful for the true power user. Things like, compilation flags and comprehensive/non-intrusive security features are way more important. I guess, the UI counts for something, but simply seeing how it "feels" is pretty much crap. I have a install of CentOS 5.6 running and its great. Its been through hell and back, the Xserver files are totally corrupt and drivers splattered, but it behaves beautifully as a server (I just use the command line to do everything most of the time). You need to test the actual features of each operating system.

What you'll find is most flavors of Linux are basically the same. Its the packages and the key features (like security) that actually take time to configure. Its these that make a good distribution noteworthy.

20. @Mark: That's interesting — I never would have guessed that something that should be so easy as installing guest additions in VirtualBox would be that easy in CentOS but would be insanely difficult in Scientific Linux.
@Anonymous: I don't dispute that my review didn't provide much insight into the positive aspects of CentOS as a server/enterprise OS, but I thought I made it pretty clear that I wouldn't do so because I don't own or manage servers, so desktop usage would be far more relevant to me than server usage. When I do these reviews, I try to evaluate how well the distributions fit my needs, and if they do, how well they meet their own stated goals. Should I have explicitly said, in addition to all that, "if you're looking for a review of CentOS with respect to its server/enterprise capabilities, please look elsewhere"? Anyway, if you read my reviews of some distributions like Kongoni, you'll see that getting some programs to work is a lot harder in some distributions than in others, and this is a function of the features of the distribution itself. If that doesn't constitute a review of desktop Linux, I don't know what does. Furthermore, I do agree that many distributions have become more similar, but as that happens, it's the little things that matter more. For example, although Fusion and Fuduntu are basically identical Fedora derivatives, I would use Fuduntu over Fusion because the former is and feels less bloated, while the latter showed random (and seemingly inconsequential) kernel panics. I hope that clears a few things up.
Thanks for the comments!

21. I hate that Centos 6 doesn't play ball with my laptop and it's wifi. Yes it's the kernal, but is it really a big deal to upgrade the kernal to the latest one? I took the bull by the horns and did so myself. It works great, I've got my wifi, and I've had no issues whatsoever.

22. @DAZZA: Well, that's the beauty of free software — if you don't like how something is done by default, you can usually change it to make it work in exactly the way you want it. Thanks for the comment!

23. @PV Yup true. At the moment I've not had any stability issues so far. Still seems to run fast as well.

24. @Anonymous: Well, it's great that it's worked for you, and hopefully that'll continue. Thanks for the comment!

25. hi i had downloaded centos and is OK. Maybe more suitable for office and corporate enviroment. [obviously] but for me could be very interesting a review of Solus OS a new distro in the block base on debian. Thanks!

1. @Anonymous: I was actually thinking of reviewing that soon. Thanks for the comment!