Overview of the 2.4 kernel

Filesystems

 

Some important features have been added to the 2.4 kernel in this field:

  • The virtual filesystem (VFS) layer has been rewritten to use only one cache now, instead of the separate write and read caches that 2.2 had.
  • The maximum file size has been pushed to an amazing 16 terbaytes now, which again improves the chances of Linux in the big iron market.
  • LIkewise, support for raw input-output has been added to the kernel, which allows certain applications (mainly databases) to read and write directly to disk bypassing the kernel, and therefore providing its own cache mechanisms.
  • Logical volume management has been added to the kernel, thus allowing users to combine multiple physical disks into a single logical disk.
  • Although no journaling filesystem has been added to the new kernel, there is a good chance that ReiserFS will be included in the 2.4.1 kernel according to the comments that I could read on the linux-kernel list. Also, SGI is about to release its own port to Linux of the XFS filesystem, and IBM is working on a port of JFS. Meanwhile, Stephen Tweedie is directing the efforts to release ext3, the journaling version most closely related to the current ext2 filesystem.

Hardware issues

 

Yet another subssytem that has been overhauled. In this case, the new improvements brought into the 2.4 kernel add some needed features for home users such as support for USB devices, together with a better scalability for enterprise uses. The following is a short list of some of these features:

  • Ctrl+Alt+Delete now performs a cold reboot instead of the traditional warm reboot. This was needed for hardware compatibility, but if you like the old type of reboot you can still enjoy it simply by adding a reboot=warm line to your lilo.conf file. Likewise, some systems may also need you to add a reboot=bios to allow reboots via BIOS.
  • Due to the use of devfs, you should now say goodbye to the old cua* devices. Instead of those, you should use the ttyS* syntax now.
  • Support for USB devices has been added to the kernel, although it only seems to work flawlessly with low-bandwidth devices such as keyboards and mice. USB modems and printers, on the other hand, may require a little bit more work to function properly.
  • The 2.4 kernel also allows to use more devices simultaneously than the 2.2 kernel ever did. Basically, you can add as many devices now as your system resources are able to take, while this was not the case before. Of course, this will benefit mainly the enterprise users.

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