You can mount ext2 as ext4 filesytem (just read...)

So - this is tough to even explain.

Imagine all of your build scripts and SOP simply read
# mkfs /dev/VolumeGroup/Volume

and then you add the following entry to /etc/fstab
/dev/VolumeGroup/Volume /directory ext4 defaults 1 2

then when you run
# mount -a

Everything is cool. Except .. it's not.

That mkfs command created an ext2 filesystem - the crappy part is when mount command is run, even though fstab is expecting ext4, it doesn't care and mounts it anyhow. So, now we have a filesystem with no Journal and added ext4 features.

Worse yet - there is no "supported" upgrade path to ext4. However, you can add a Journal to make it ext3.
# tune2fs -j /dev/VolumeGroup/Volume

Comments

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