Ext4 is the normal evolution of the most used Linux filesystem: Ext3. The evolution of Ext3 from Ext2 had add just 1 new important feature: journalization. But ext4 is a result of hardly improved Ext3 and is coming with better performance, modified data structures, reliability and new features like bigger filesystem/file sizes, subdirectory scalability, extents, multiblock allocation, delayed allocation, journal checksumming, online defragmentation, persistent preallocation.

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I think, everyone from Linux industry, knows about kexec (fast rebooting … actually not rebooting just switching kernels) or Pannus (live kernel patching, but right now the project is dead) and their use. The Linux community started very earlier to think at a method to switch or patch a live kernel, but this things should work only on a very good kernel with very good memory and process isolation … but this was achieved some time ago, we have a very good and mature Linux kernel (in my opinion was perfect from 2.4.2x) what can run for years without a reboot (my record is 4 years on a system with kernel 2.6.8 and this kernel is far to be perfect). This days I found a tool what is a gold mine for system administrators : KSplice.

Yes, is possible and is very easy. Ext2 differ from Ext3 only on few things: Journalling is one of them and can be added very easy to an Ext2 system. First, just look to the features of a Ext2 filesystem:

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By default, a Linux, is waiting direct input of a person / sysadmin when is crashing with kernel panic/oops. Obviously is very important to know or to see directly the dumped screen, but sometimes in production environments is better just to reboot itself without any intervention and debug the problem with the system online. Off course for debugging and seeing the dump you will need to install and configure kdump, but that is another story (I will probably write about that soon).

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If you reached this page is possible to know what a core dump is, but I will explain again (in a very short version) for the new “kids” on the Linux who also is possible to reach this page … it sounds like a paradox … whatever:

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