Why was UFW removed automatically?

Question

I noticed that the package UFW had been removed from a server, but do not recall having manually removed it. Looking at the logs at /var/log/apt/history.log, I noticed this entry:

Start-Date: 2024-06-24  18:56:55
Commandline: apt-get install -y iptables-persistent
Requested-By: ealfonso (1000)
Install: iptables-persistent:amd64 (1.0.20), netfilter-persistent:amd64 (1.0.20, automatic)
Remove: ufw:amd64 (0.36.2-1)
End-Date: 2024-06-24  18:57:06

I did request iptables-persistent to be installed. Does the log above indicate that the UFW removal was triggered by installing iptables-persistent?

From the iptables-persistent package description there doesn't appear to be a direct conflict with UFW, and according to this answer, UFW can be compatible with iptables-persistent.

Answer 1

If you run apt show ufw, you’ll see:

[…]
Breaks: iptables-persistent, netfilter-persistent
[…]

So ufw can’t be installed at the same time as either iptables-persistent or netfilter-persistent, and this is enforced by apt. The reasoning is given in ufw’s changelog:

Breaks with iptables-persistent and netfilter-persistent. When ufw is installed, it is not enabled by default, so it doesn't interfere with other firewall software (until it is enabled). In contrast, iptables-persistent and netfilter-persistent install enabled, which interferes with ufw. Add a breaks on these to avoid them being co-installed with ufw (and causing problems for users).