ufw remains disabled after a reboot using Ubuntu Server 16.04

My server uses ufw to set up a simple firewall. I noticed however that the ufw firewall remained disabled after a reboot: ufw status reported "disabled" always.

I checked the following:

• The /etc/ufw/ufw.conf file contained ENABLED=yes.

• The service was correctly registered with systemctl, and looking in the /var/log/syslog file I could see the line "Starting Uncomplicated firewall", which proved it was at least started

• A very odd thing was that even though the firewall was saying it was disabled the system log still showed audit log lines.

• iptables -L showed that indeed all of the usual configuration was gone.

Solution 1:

The cause of this problem was that the service netfilter-persistent (also called iptables-persistent on other distributions) was enabled on the system, and this ran after ufw was disabled. This overwrote the ipfilter configuration from ufw.

I disabled netfilter-persistent:

$ sudo systemctl disable netfilter-persistent

and after that booting properly enabled ufw.