In the Webmin Users module, click on Disk Quotas next to the name of the user that you want to restrict.

Set the Can edit module configuration? field to No, so that the user cannot change the commands used for setting and getting quotas.

To restrict the filesystems on which quotas can be assigned, change the Filesystems this user can edit field to Selected and choose them from the list below.

Set the Can enable and disable quotas? field to No, unless the user is responsible for all user and group quotas on the allowed filesystems—otherwise he will be able to turn off quotas for users that he is not allowed to edit.

Change the Can configure quotas for new users? field to No, so that he cannot change the quotas that are assigned to users created in the Users and Groups module. Only if the Webmin user is allowed to edit all quotas on a filesystem should this be left set to Yes.

If you do not want this Webmin user to change grace times, set the Can edit user grace times? and Can edit group grace times? fields to No.

To stop the user from handing out massive disk quotas, set the Maximum grantable block quota and Maximum grantable file quota fields to the maximum blocks and files that can be granted to any one user, respectively. There is nothing, however, to stop him granting quotas to multiple users that add up to more than these limits.

To restrict the UNIX users whose quotas can be edited, change the Users this user can edit quotas for field from All users to one of the other options. The most useful is Users with UID in range, which restricts access to those users whose UIDs lie within the minimum and maximum numbers entered into the fields next to it. It is usually a bad idea to allow the editing of the root user's quotas, as setting it too low may prevent the system from creating important PID, mail, and lock files. You can prevent this by selecting All except users and entering root into the field next to it, assuming that you want to allow the editing of every other user. To stop the Webmin user editing any user quotas at all, select the Only users option and enter nothing into the field next to it.

Similarly, you can limit the groups whose quotas can be edited by changing the Groups this user can edit quotas for field. Naturally, this only has an effect on filesystems that have group quotas enabled.

When done, click the Save button to have the restrictions applied immediately.