Why does Pure-FTPd fail to restart when CallUploadScript is enabled?

Symptoms

If you enable the CallUploadScript directive in the Pure-FTPd configuration file and the pure-upload process is not running, Pure-FTPd fails to restart.

Description

Imunify360 requires CallUploadScript to scan files uploaded via FTP. However, if the pure-upload process is not running, when you try to restart Pure-FTPd, you see errors like these:

Cpanel::Exception::Services::StartError
Service Status
 pure-ftpd (/usr/sbin/pure-ftpd --daemonize -A -c50
-B -C8 -D -E -fftp -H -I15 -lextauth:/var/run/ftpd.sock -L10000:8 -m4
-p49152:65534 -s -S21 -U133:022 -u100 -i
-Oxferlog:/etc/apache2/logs/domlogs/ftpxferlog -o -k99 -Z -Y1
-JHIGH:MEDIUM:+TLSv1:!SSLv2:+SSLv3) running as root with PID 1983324
(process table check method)

Service Error
 (XID eet6t6) The “pureftpd” service failed to start.

Workaround

Disable CallUploadScript with these steps:

1. Create a local PureFTPd template file:

   cp -a /var/cpanel/conf/pureftpd/main /var/cpanel/conf/pureftpd/local

2. Disable the CallUploadScript option in the file:

   [root@server]# vi /var/cpanel/conf/pureftpd/local
   [root@server]# grep CallUploadScript /var/cpanel/conf/pureftpd/local
   CallUploadScript: 'no'

3. Rebuild the Pure-FTPd configuration file:

   /scripts/setupftpserver pure-ftpd --force

4. Verify that Pure-FTPd restarts:

   /scripts/restartsrv_pureftpd