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Randomly getting stuck on boot after enabling UFW

ms flag
Karsten

I tried to diagnose this problem for a few weeks from now, tried everything I could do (except disabling ufw) but to no avail.

System: Kubuntu 21.04 with kubuntu-ppa/backports

What I tried to do: Enable UFW through sudo ufw enable

What happened: Whenever I enabled UFW, the system may get stuck when booting / rebooting. There is no indication where the system got stuck. Entered tty on boot, found systemd-hostnamed loaded but failed to activate. Reason was timeout.

What I tried to do:

  1. Disable networkmanager-wait-online.service

  2. Disable NetworkManager's connectivity check

  3. Attempting to start and save UFW rules with the dispatcher script from https://help.ubuntu.com/community/IptablesHowTo#Solution_.233_iptables-persistent

Error messages: https://imgur.com/K5FWGAK

Now this is frustrating, because I did set WatchdogSec=1min and DefaultStartTimeout=10s and DefaultStopTimeout=10s, none of it seemed to affect service timeout during boot.

It seems that UFW is conflicting with NetworkManager / systemd-hostnamed / DNS service. Of course, disabling ufw solves the problem, but not an option. This never happened to me on Ubuntu with the same set of applications installed, so I doubt it is VPN or other network services affecting this.

Edit #1: sudo ufw status verbose output:

karsten@karsten-kbt-pc:~ (・∀・)> sudo ufw status verbose
[sudo] password for karsten: 
Status: active
Logging: on (low)
Default: reject (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
80/tcp                     ALLOW IN    Anywhere                  
443                        ALLOW IN    Anywhere                  
53                         ALLOW IN    Anywhere                  
6881                       ALLOW IN    Anywhere                  
8881/udp                   ALLOW IN    Anywhere                  
1401/tcp                   ALLOW IN    Anywhere                  
1194:1197/udp              ALLOW IN    Anywhere                  
1300:1303/udp              ALLOW IN    Anywhere                  
1400/udp                   ALLOW IN    Anywhere                  
51820                      ALLOW IN    Anywhere                  
80/tcp (v6)                ALLOW IN    Anywhere (v6)             
443 (v6)                   ALLOW IN    Anywhere (v6)             
53 (v6)                    ALLOW IN    Anywhere (v6)             
6881 (v6)                  ALLOW IN    Anywhere (v6)             
8881/udp (v6)              ALLOW IN    Anywhere (v6)             
1401/tcp (v6)              ALLOW IN    Anywhere (v6)             
1194:1197/udp (v6)         ALLOW IN    Anywhere (v6)             
1300:1303/udp (v6)         ALLOW IN    Anywhere (v6)             
1400/udp (v6)              ALLOW IN    Anywhere (v6)             
51820 (v6)                 ALLOW IN    Anywhere (v6)
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ufw
in flag
matigo
Two questions for you: (1) is IPv6 enabled in UFW? (2) what is the outgoing policy for the system?
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ms flag
Karsten
@matigo 1) Yes, rules for ipv6 enabled 2)Allow outgoing reject incoming by default
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in flag
matigo
Weird. Could you [edit] your question to include the output of `sudo ufw status verbose`? This will show the complete list of rules that the "uncomplicated" firewall is using, and it may reveal something.
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ms flag
Karsten
@matigo included the output. This happened even without any rules and was why I added rules.
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in flag
matigo
Hmm ... the only difference I can see with your rules and the ones I have on servers is the incoming value is set to `reject` (as you also stated in a comment), whereas the default is generally `deny`. I don't *think* that should make a difference, though
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ms flag
Karsten
@matigo it is set to `reject` with plasma-firewall, I don't know if `deny` will make a difference though.
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