Frequently Asked Questions

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Getting Started

Where do I get the latest version of e2fsprogs?

The latest version of e2fsprogs can be found at Soureforge or at

How do I build e2fsprogs?

The INSTALL file in the top of the source tree gives more detailed information, but e2fsprogs uses a standard configure script, so the standard "./configure; make" will build the e2fsprogs binaries. Note that if you wish to build the ELF shared libraries, you need to add the "--enable-elf-shlibs" option to the configure invocation.

How do I mount a fresh new storage device as ext4?

For example, if the new device has been detected as /dev/sdb1 (check "dmesg" output):

Using the newly installed e2fsprogs:

cd misc/
mke2fs -E test_fs /dev/sdb1
cd debugfs/
./debugfs -w /dev/sdb1
debugfs 1.40.5 (27-Jan-2008)
debugfs: set_super_value s_flags 4
debugfs: quit

blkid /dev/sdb1
/dev/sdb1: UUID="3aa983ef-0dcd-474d-a9d3-2660ff6ef3e7" TYPE="ext4dev"
mkdir /mnt/test
tune2fs -j /dev/sdb1
mount -t ext4dev /dev/sdb1 /mnt/test

Why do I get "EXT4-fs: sdb1: not marked OK to use with test code." in my dmesg?

This error arises from not executing the "mke2fs -E test_fs /dev/sdb1", which will label

How do I turned off the mballoc feature?

By default "mount" will enable mballoc feature when mounting. To turn it off:

mount -t ext4dev -o data=writeback,delalloc,extents,nomballoc /dev/sdb1 /mnt/test

How do I turned off the extent feature?

By default "mount" will enable extent feature when mounting. To turn it off:

mount -t ext4dev -o data=writeback,delalloc,noextents,mballoc /dev/sdb1 /mnt/test

CAUTION: Once extent feature has been turned on, it is not possible to mount it as ext3 anymore.

Why do I get "EXT4-fs: Unrecognized mount option "delalloc" or missing value"?

Please download the ext4 version from the git patchset, instead of using the kernel source.

What is mballoc feature? After I mounted a partition as mballoc, can I remount it as nomballoc?

Yes, it is possible, just dismount the partition first, and execute "mount" with the nomballoc feature.

Understanding how it works

What are the new features in Ext4 (vs Ext2/3)?

How do I test the features in Ext4?

What external tools are available for testing Ext4 FS?

How do I benchmark the performance of Ext4 as against other FS? What are the tools available?

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