# apt install ufw
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
liblockfile-bin liblockfile1 lockfile-progs sendmail-base sensible-mda
Use 'apt autoremove' to remove them.
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 108 not upgraded.
Need to get 147 kB of archives.
After this operation, 849 kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 ufw all 0.36-6ubuntu1 [147 kB]
Fetched 147 kB in 1s (259 kB/s)
Preconfiguring packages ...
Selecting previously unselected package ufw.
(Reading database ... 100288 files and directories currently installed.)
Preparing to unpack .../ufw_0.36-6ubuntu1_all.deb ...
Unpacking ufw (0.36-6ubuntu1) ...
Setting up ufw (0.36-6ubuntu1) ...
Creating config file /etc/ufw/before.rules with new version
Creating config file /etc/ufw/before6.rules with new version
Creating config file /etc/ufw/after.rules with new version
Creating config file /etc/ufw/after6.rules with new version
Created symlink /etc/systemd/system/multi-user.target.wants/ufw.service → /lib/systemd/system/ufw.service.
Processing triggers for rsyslog (8.2001.0-1ubuntu1.3) ...
Processing triggers for systemd (245.4-4ubuntu3) ...
# ufw status
default rules in /etc/ufw/user.rules;
i've added one rule for aaPanel's port, then:
# sudo ufw enable
Command may disrupt existing ssh connections. Proceed with operation (y|n)? y
Firewall is active and enabled on system startup
then retest security check in aaPanel was good = problem solved;
then i've restarted SYS Firewall 2.7 in aaPanel. restarted normally.
but got this one again:
# sudo ufw status
and then retest security check in aaPanel was good = problem back;
Check whether the system firewall is enable（Checked: 8minutes ago, time: 99.29ms）