Updating to ext4
Ext3 was mostly about adding journaling to Ext2, but Ext4 modifies important data structures of the filesystem such as the ones destined to store the file data. If the inode count is too low, no file can be created on the filesystem even though there is still space left on it.
The result is a filesystem with an improved design, better performance, reliability, and features. Because it is not possible to change either the bytes-per-inode ratio or the inode count after the filesystem is created, uses by default a rather low ratio of one inode every 16384 bytes (16 Ki B) to avoid this situation.
Otherwise, you risk being unable to decrypt files on filesystem A if filesystem B is unmounted.
Alternatively, you can use the E4rat is a preload application designed for the ext4 filesystem.
In a directory tree marked for encryption, file contents, filenames, and symbolic link targets are all encrypted. See also Quarkslab's blog entry with a write-up of the feature, an overview of the implementation state, and practical test results with kernel 4.1.After a few minutes (depending on the size of your partitions and the amount of data on them), everything will go back to normal and you’ll be able to log in again. You should get a message indicating the operation was successful.If you are upgrading from 8.04 LTS to 10.04 LTS, you will need to install grub2 as soon as possible, as grub1 is not Ext4-aware.It ensures that file system metadata is correctly written and ordered on disk, even when write caches lose power.This goes with a performance cost especially for applications that use fsync heavily or create and delete many small files.
However, for partitions with size in the hundreds or thousands of GB and average file size in the megabyte range, this usually results in a much too large inode number because the number of files created never reaches the number of inodes.