secure ftp with vsftp without remote shell login

[Johan Mares]

SL5.0 webserver, I created a user for every 'customer' with no shell 
login (sbin/nologin). The users home = /var/www/html/name-of-site/htdocs.
In vsftpd.conf I made sure that they cannot leave their home dir (chroot 
jail). Some 'customers' want to use secure ftp, but then I have to give 
them shell login.
Is there a possibility to let users choose wether they want to use FTP 
or SFTP without giving them remote shell login ?

thanx,
Johan Mares

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VLIZ
Flanders Marine Institute