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I've been unable to successfully mount an ext4 formatted drive to any of my EC2 instances. All are running CentOS 5.6 (32 and 64-bit mix) all successfully yum upgraded from one of public RightScale AMIs (originally CentOS 5.4) with some of the Rightscale stuff edited/removed as needed.

The error is always when mounting:

# mount -t ext4 /dev/sdf /test
mount: unknown filesystem type 'ext4'

I've tried installing the latest e2fsprogs and e4fsprogs packages (also compiled from the latest e4fsprogs release) and tried 'mke2fs -t ext4' and 'mke4fs' with the same error every time when mounting. Formatting to ext2 will always mount just fine.

Is there a boot time option I need to change or something missing from the Kernel I can verify or change?

FYI: I installed a local CentOS 5.6 virtualbox instance and can mount an ext4 drive just fine using the same commands, so my assumption is it's something with EC2 or the RightScale image I used to upgrade to CentOS 5.6.

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migrated from Sep 4 '11 at 3:09

This question came from our site for professional and enthusiast programmers.

I believe you still need the ext4 module loaded in order for this to work:

sudo /sbin/modprobe ext4

Additionally, you can have this module loaded automatically by adding ext4 to /etc/modprobe.conf.

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I think I need to choose a custom Kernel when spinning up a new AMI, the one I'm using is not configured for ext4 :( – Richard Sep 2 '11 at 1:33
CentOS 6 has support for EXT4 built-in, if that helps. – SpacemanSpiff Sep 4 '11 at 4:59

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