quota change in Linux kernels from 2.4 on.

Tested on Scientific Linux 6.1

Quota changes break Webmin/Virtualmin. "man convertquota" says it best:

convertquota converts old quota files quota.user and quota.group to files aquota.user and aquota.group in new format currently used by 2.4.0-ac? and newer or by SuSE or Red Hat Linux 2.4 kernels on filesystem.

   New  file  format  allows  using  quotas for 32-bit uids / gids, setting quotas for
   root, accounting used space in bytes (and so allowing use of  quotas  in  ReiserFS)
   and  it is also architecture independent. This format introduces Radix Tree (a sim-
   ple form of tree structure) to quota file.

There appears no way to make it work with webmin/virtualmin, so restoring virtualmin domains fail. And no, you can't convert from new to old.

virtualmin restore domain output:
"Restore failed : setquota: Cannot open quotafile /home/quota.user: No such file or directory setquota: Not all specified mountpoints are using quota. "

And yes, virtualmin's check disk quota works fine.