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Ext4 is an improved FileSystem for Linux, introduced in kernel 2.6.28. Previous kernels had development implementation (i.e. experimental). For more information about Ext4, follow the links in the See Also section.

Compatibility:

Things you need to know

ext4 is a journaling file system, meaning it maintains a journal of operations not yet committed to disk, and is able to prevent some amount of data loss after a system crash or power failure. If an ext4 filesystem is determined "unclean" on boot (traces of remaining operations in the journal), the system will run fsck and attempt to repair the filesystem, and write uncommited blocks to the lost+found/ directory. At the very least, the filesystem will be restored to a working state.

File system check with fsck.ext4

As of systemd the old 'touch /forcefsck ' no longer works instead you have to edit /etc/default/grub and add a "fsck.mode=force" to your kernel command line (you may have other bits - just add it between the quote marks)

GRUB_CMDLINE_LINUX="fsck.mode=force"

Then do an update-grub and reboot.

Afterward remove the fsck bit and update-grub again.

(This really needs to be made easier -- worth a bug report.)

De-fragmenting

$ e4defrag /dev/sd?

Status

Ext4 in stretch, jessie, Squeeze, testing and Unstable

Ext4 in Lenny

FAQ

How to mount an Ext4 filesystem under Lenny

Lenny doesn't really/officially support Ext4 (because it's experimental in its kernel version). Still, you can try to mount an Ext4 filesystem in read-only mode... and see what you see !

tune2fs -E test_fs /dev/XXX
mount -t ext4dev -o ro /dev/XXX /mnt/ZZZ
How to convert Ext3 to Ext4

See the Ext4 HOWTO on the Ext4 Wiki of kernel.org.


See also


CategoryKernel | ?CategoryFileSystem | CategorySystemAdministration