And check that the group permissions of the folder allow "group" to read/write to /var/www. If you wish for the user to retain their home directory then just add it as a secondary group. If the user is specifically just to upload data to /var/www then you make make www-data their only group and make /var/www their home directory so FTP will automatically open there by default.
Assuming you aren't familiar with Linux command line, Webmin is probably the easiest way to do all this. "Users & Groups" (for the settings related to the user) and "File Manager" (for setting/checking file permissions - click the folder in the right pane and click Info button) are the modules you'll need to use.
Also remember that you'll need to use SFTP not just FTP.
Make the user a member of www-data group
And check that the group permissions of the folder allow "group" to read/write to /var/www. If you wish for the user to retain their home directory then just add it as a secondary group. If the user is specifically just to upload data to /var/www then you make make www-data their only group and make /var/www their home directory so FTP will automatically open there by default.
Assuming you aren't familiar with Linux command line, Webmin is probably the easiest way to do all this. "Users & Groups" (for the settings related to the user) and "File Manager" (for setting/checking file permissions - click the folder in the right pane and click Info button) are the modules you'll need to use.
Also remember that you'll need to use SFTP not just FTP.