For example, if you use max-users=50, there will be up to 52 ncftpd processes running at any one time; one for each user, a logger process and a main process. There could also be other processes created by NcFTPd if you enable the on-the-fly TAR feature.
The number of users to use for max-users varies for each site, but you shouldn't use a number higher than your system could handle. I.e., if your system can't handle 1000 active processes, don't set max-users to 1000 :-)
Examples:
