systemd

Useful Debian systemd commands

 systemctl [start|stop] apache2

 systemctl status
 systemctl status  apache2 
 
 systemctl edit apache2 # will edit the override file with nano

 systemctl restart postgrey

See the journal

 journalctl -u mariadb
 journalctl -u apache2

bind / dns

 systemctl reload bind9

and iptables

To clear all iptables entries, first stop fail2ban, then clear, then restart fail2ban

 iptables --policy INPUT   ACCEPT;
 iptables --policy OUTPUT  ACCEPT;
 iptables --policy FORWARD ACCEPT;

 iptables -Z; # zero counters
 iptables -F; # flush (delete) rules
 iptables -X; # delete all extra chains