'dd' failure at launch of fstransform about fstransform

[cosmos72]

Hi @rswarthout
the error you posted

17:45:36 dd: failed to truncate to 32635174780927 bytes in output file '/virtual_0/.fstransform.loop.308145': File too large

indicates that the initial file system type (ext4) does not support creating the huge sparse file
(32.6 TB, as large as the device itself) needed by fstransform.

Wikipedia (https://en.wikipedia.org/wiki/Ext4#Features) says that maximum file size supported by ext4 is 16 TiB = 17.6 TB,
so it matches your issue.

While this problem is in theory relatively easy to workaround in fstransform (by splitting the huge sparse file into multiple files, and using dmsetup instead of mount -t loop to create a single block device on top of them), it would require some development.

In summary, there is currently no way to convert an ext4 file system larger than 16 TiB with fstransform. Sorry.

[rswarthout]

@cosmos72 Thank you for getting back to me on this. I will proceed with doing a copy of the data to another volume.