Raspberry Pi OS

Disable WiFi and Bluetooth
1. Through boot configuration
2. Through rfkill
Swap
Run containers
1. Kernel containerization features
2. Firewall settings
Store files on the SD even when the overlay file system is active
Further readings
Sources

Disable WiFi and Bluetooth

Through boot configuration

Disable one or both in the all section of /boot/config.txt:

[all]
dtoverlay=disable-wifi
dtoverlay=disable-bt

Through rfkill

block one or both:

rfkill block wifi
rfkill block bluetooth

check they are correctly soft-blocked:
```
rfkill list
```

Swap

Disable the swap file.

sudo systemctl disable --now 'dphys-swapfile'

Run containers

enable the kernel's containerization feature
disable swap
if kubernetes is involved, set up the firewall to use the legacy configuration

Kernel containerization features

Enable containerization features in the kernel to be able to run containers as intended.

Add the following properties at the end of the line in /boot/cmdline.txt:

cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1

sed -i '/cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1/!s/\s*$/ cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1&/' /boot/cmdline.txt

Firewall settings

Switch Debian firewall to use the legacy configuration:

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

Store files on the SD even when the overlay file system is active

The files just need to be stored on a different file system from /. You can partition the SD and use that, or create a file and mount it as a virtual file system:

truncate -s '6G' 'file'
mkfs.ext4 'file'
mkdir 'mount/point'
sudo mount -t 'ext4' -o 'loop' 'file' 'mount/point'
sudo chown 'user':'group' 'mount/point'
touch 'mount/point/new-file'

Sources

The k3s project page
The Build your very own self-hosting platform with Raspberry Pi and Kubernetes series of articles
Run Kubernetes on a Raspberry Pi with k3s
Project's issue 2067

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