Why is it that so many people still use kernel 2.4? Isn't 2.6 better? Why do so many distros come with v2.4 standard? And, for that matter, what happened to 2.5? Did it suck?

2.4.x is proven to be reliable and many corporations depend on it for customized programming, code and applications.

2.5.x is development only. All odd numbers are development packages, all even numbers are production or proven to be stable releases. 2.5.x led up to the 2.6.x release, as 2.3.x led up to the release of 2.4.x

2.6.x is not necessarily better, it just supports more hardware and has more features, not necessarily used by the masses. Hardware is costly in a data center, you don't necessarily update your hardware cause there's a new kernel out to support it.

In my recent experience, 2 reasons to have a 2.6.X kernel: SATA and Wireless
Reasons to have a 2.4.X kernel: 0

In addition, the other real differences are in the threading. since kernel 2.2 the threaded processes support has improved with each stable version.

Unfortunately, while a lot of commercial and corporate use does require the 2.4 kernel, most distros that the end user want do default to the 2.6 kernel. This means that the mutlimedia tools, including dvd playback, that most people want is killed if they need a commercial application.
[ Borland's Kylix will not install on a 2.6 kernel system, so to use the development tool you need to have the 2.4 kernel. ]

Most commercial use of Linux is servers and development environments, where the multimedia stuff is not needed on the systems.

Let's not forget that kernel 2.6 brings vast improvements on kernel scheduling and memory use -- not just hardware. For these reasons, it's vastly superior when running multi-threaded applications or servers with multiple processes.

Oh yeah -- it's not that simple when comparing RHEL3 (kernel 2.4) since they have their own code + backports.

DVD playback works with a 2.4 kernel.

Some distributions still come with 2.4 because developers of them understand that they may be used on older systems where 2.6 is way too heavy.

Has there really been fresh releases with 2.4 still?
I'd thought that most of the 2.4 distros were simply delivered before 2.6 had been tested enough.

Look at kernel.org It seems that 2.4 is still actively maintained. 2.2 is listed, but has no recent activity.

Debian still defaults to kernel 2.4.27

I don't know at what point something is considered "unmaintained"

I believe they did make it official that 2.2 was no longer going to be maintained, probably the reason there's no activity on it.

They don't want to do the work that it takes to convert to 2.6. It's the same with alot of software. Look how many still ship Apache 1.x when the current version is 2.2.3, two whole series ahead. To quote their site "This version of Apache is a major release and the start of a new stable branch, and represents the best available version of Apache HTTP Server."

Consider you'll have to recompile glibc, add TLS, switch over to NPTL, (which can not be done on a live system, learned this the hard way) likely replace the accounting tools to handle the new accounting format, change a ton of scripts that assume 2.4-isms, make sure .ko modules are handled instead of .o modules, add in /sys, /config, and friends, rework things such as NFS to take advantage of new features, etc. Then there's the breakage: several programs have to be recompiled, others replaced, and so on. The two kernel versions require different GCC versions to compile (4.x will not compile 2.4's) so you'd have to change over compilers as well. Not to mention that the kernel headers are radically different for 2.6 and thus a bunch of stuff that used them will break. I went thru this, so I know the headache firsthand. Some are trying to add it in slowly, with mutations such as the /lib/tls stuff, LD_* environmental variables to fake kernel versions, and other hacks that IMO just make the system more complex and less robust. Since you can build kernels how you want, I don't think saying 2.4 is small or better for lesser systems really holds true. In fact, my 2.6 kernels are actually smaller in bytes than the 2.4 series for the same hardware.


But 2.6 is way better and I would not go back for any reason. I used to be a supporter of standing with 2.4, but when I really saw all the improvements in 2.6, I changed my mind. That's one of the greatest things about linux: you can build a 2.0 system if that's what floats your boat. Or 2.4 or whatever.


The latest is the greatest, that's my

Not as well as with the 2.6 kernel. the udev utilitity that works with raw block devices such as dvd drives requires the 2.6 kernel.

I've used both kernels with a dvd, and the 2.6 is about a thousand% better with all multimedia [ desktop and end user entertainment ] than the 2.4 series.

Reason to use the 2.4 kernel:
to be able to use that $1,500.00+ commercial program you bought for commercial use.
[ to make money ] You know, the one that won't run on anything but a 2.4 kernel.