ubuntu 9.04 upgrade ext3 to ext4 question about "Group Descriptor Checksum invalid" from fsck

[Lucio M Nicolosi]

On Mon, Apr 27, 2009 at 9:54 PM, Paul Johnson <pauljohn32 at gmail.com> wrote:
> I followed these instructions (after upgrading Ubuntu)
>
> http://blog.taragana.com/index.php/archive/upgrade-ubuntu-810-to-ubuntu-904-and-ext3-to-ext4/
>
>  to boot from the DVD and then run the commands to change a partition
> from ext3 to ext4.   I'm curious to know what the errors mean "Group
> descriptor X checksum is invalid" hundreds of times.
>
> What do these things mean? Did I guess wrong when I said y to fix?
>
> $ sudo /sbin/tune2fs -O extents,uninit_bg,dir_index /dev/sda5
> tune2fs 1.41.4 (27-Jan-2009)
>
> Please run e2fsck on the filesystem.
>
> $ sudo /sbin/e2fsck -fD /dev/sda5
> e2fsck 1.41.4 (27-Jan-2009)
> Group descriptor 0 checksum is invalid.  Fix<y>? yes
>
[]
>
> Group descriptor 226 checksum is invalid.  Fix<y>? yes

> --
> Paul E. Johnson

Are you sure you want to use ext4 right now?

from:

https://wiki.ubuntu.com/JauntyJackalope/ReleaseNotes#line-145

"Lock-ups when deleting files from ext4 filesystems

In some cases, deleting files from an ext4 filesystem is reported to
cause soft lock-ups in the kernel (330824). Investigation of this
problem is ongoing, and it is expected that a fix for this problem
will be made available as a post-release update. To avoid this
problem, users may wish to install using the default ext3 filesystem
and convert their filesystem to ext4 (as documented on the ext4 wiki)
once a fix is available.

Switching to ext4 requires manually updating grub

If you choose to upgrade your / or /boot filesystem in place from ext2
or ext3 to ext4 (as documented on the ext4 wiki), then you must also
use the grub-install command after upgrading to Ubuntu 9.04 to
reinstall your boot loader. If you do not do this, then the version of
GRUB installed in your boot sector will not be able to read the kernel
from the ext4 filesystem and your system will fail to boot.

Possible data-loss problems resizing ext4

The resize2fs tool may cause data loss when growing or shrinking ext4
filesystems off-line. See this mail from the upstream maintainer for
more details. Unfortunately we became aware of this too late to fix it
in Ubuntu 9.04. If you wish to resize an ext4 filesystem using the
tools in Ubuntu 9.04, you may be able to work around these problems by
first disabling the flex_bg and uninit_bg features (do not attempt
this on a mounted filesystem!):

tune2fs -O ^flex_bg,^uninit_bg /dev/DEVICE_NAME
e2fsck /dev/DEVICE_NAME

However, we still strongly recommend taking significantly more care
with backups than usual before attempting to resize an ext4
filesystem."


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L M Nicolosi, Eng.
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