By default, the Ampere A1-based ARM64 VMs from Oracle Cloud with Ubuntu 24.04 come with some unwanted defaults for a K3s Kubernetes setup.

## Changes

These were the changes made to each instance:

1.  Remove iptables rules
    

```sh
# Apply live
sudo iptables -D FORWARD -j REJECT --reject-with icmp-host-prohibited 2>/dev/null
sudo iptables-legacy -D FORWARD -j REJECT --reject-with icmp-host-prohibited 2>/dev/null

# Persist changes
sudo vim /etc/iptables/rules.v4

# COMMENT OUT OR DELETE:
# -A INPUT -j REJECT --reject-with icmp-host-prohibited
# COMMENT OUT OR DELETE:
# -A FORWARD -j REJECT --reject-with icmp-host-prohibited
```

2. Increase limits via sysctl

```sh
# Apply live
sudo sysctl fs.inotify.max_user_watches=524288
sudo sysctl fs.inotify.max_user_instances=512

# Persist changes
echo "fs.inotify.max_user_watches=524288" | sudo tee -a /etc/sysctl.d/99-kubernetes.conf
echo "fs.inotify.max_user_instances=512" | sudo tee -a /etc/sysctl.d/99-kubernetes.conf
sudo sysctl --system
```

3.  Use legacy iptables backend
    

```sh
update-alternatives --set iptables /usr/sbin/iptables-legacy
update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy
```

## Additional notes

*   Do NOT run Docker alongside K3s.
    
*   Do NOT use `ufw` / `firewalld` or any other firewall.