General help

To expand on the previous reply:

Download a CSV file of students

1. Go to Site administration ▸ Users ▸ Bulk user actions.
2. Under New filter click Show more....
3. Find Course role:
   1. Change any role to Student.
      
      
   2. At the end of the list click Add filter.
4. Under Users in list in Users select All filtered then click Add to selection.
   
   
5. At the bottom of the page in With selected users... select Download and click Go.
6. In Export users as leave this as Comma separated values (.csv) and click Download and save the file.
   

Add the new username in the CSV file

1. Open the downloaded file in a spreadsheet program, e.g. Excel.
2. Change the first row of the username column to oldusername.
3. Insert a new column, e.g. column B, and enter username in the first row. This column will contain the new username.
   
4. In row 2 of this column enter the new username using a formula. If the email address is in column D in LibreOffice Calc this would be =LEFT(D2, SEARCH("@", D2) - 1), it may be the same in Excel.
   
   
5. Copy and paste this formula into the remaining rows.
6. Save the file. This must be saved as in CSV format (not .xlsx, .ods, etc.).
   

Upload the updated CSV file

1. Go to Site administration ▸ Users ▸ Upload users.
2. Select the updated CSV file and click Upload users.
   
3. On the Upload users preview page under Settings:
   1. change Upload type to Update existing users only,
   2. change Allow renames to Yes.
      
      
4. Click Upload users.
5. The Upload users results page should show the username change as expected.