Raspberry Pi K3s Alpine Linux Part 1

Oct 23, 2022

Vietnamese version can be read at Vie-Ver.

A couple of days ago, Interesting. I cleaned warehouse and found out two raspberries

one is 3b+ and the other is 4B. It's also a pity to quit, so spending some free time creating k3s cluster to play around. Making it difficult for myself, I decided to install alpine linux for them.

Setup OS

Download the Raspberry Pi build.

Which version should I install?
There are currently three versions of Alpine for Raspberry Pi: armhf, armv7, and aarch64. The aarch64 build should be compatible Raspberry Pi 3 and Compute Module 3, and Raspberry Pi 4 Model B. i will choice aarch64.
```
cd /tmp
wget https://dl-cdn.alpinelinux.org/alpine/v3.16/releases/aarch64/alpine-rpi-3.16.2-aarch64.tar.gz
```

Partition and format the memory card.

I using Raspbian to create usb alpine boot for rpi. Install GNU Parted (parted) if not available.

sudo apt install parted

First of all Insert the SD card and check it have been existed. My sd card is sda.

$ lsblk
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda           8:0    1 58.2G  0 disk 
`-sda1        8:1    1 58.2G  0 part /media/pi/SDCARD
mmcblk0     179:0    0 29.7G  0 disk 
|-mmcblk0p1 179:1    0  256M  0 part /boot
`-mmcblk0p2 179:2    0 29.5G  0 part /

Create a small partition for /boot, then allocate the rest of the disk to a separate partition.

sudo parted /dev/sda --script -- mklabel msdos
sudo parted /dev/sda --script -- mkpart primary fat32 1 256M
sudo parted /dev/sda --script -- mkpart primary ext4 256M 100%

Format the boot partition to FAT32 and the rest is ext4:

sudo parted /dev/sda --script -- set 1 boot on
sudo parted /dev/sda --script -- set 1 lba on
sudo mkfs.vfat -F32 /dev/sda1
sudo mkfs.ext4 /dev/sda2

Verify by printing the partition table.

$ sudo parted /dev/sda --script print
Model:  SD Card Reader (scsi)
Disk /dev/sda: 62.5GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
1      1049kB  256MB   255MB   primary  fat32        lba
2      256MB   62.5GB  62.3GB  primary  ext4

Mount the boot partition.

sudo mkdir /mnt/sd
sudo mount /dev/sda1 /mnt/sd

Unpack the Alpine package onto the partition.

# i have download alpine image at /tmp in step-1
sudo tar xf /tmp/alpine-rpi-**.tar.gz -C /mnt/sd --no-same-owner

Create the usercfg.txt file into the boot partition: /mnt/sd/usercfg.txt.

# Enable mini UART as serial port (/dev/ttyS0).
# Also, fixes VideoCore IV (aka the GPU or the VPU) frequency to 250MHz.
enable_uart=1

# give the GPU the least amount of RAM it can get by with (16MB).
# This also triggers the Pi to use a cutdown version of the firmware (start_cd.elf).
gpu_mem=16

# Optionally turn off audio and bluetooth.  (Note "dt" stands for device tree)
dtparam=audio=off,pi3-disable-bt

Headless Installation (optional)
If you don’t have direct access to your system, such as via a display and keyboard you can install Alpine with the overlay directory structure and headless script.
```
sudo curl -L -o /mnt/sd/headless.apkovl.tar.gz https://github.com/davidmytton/alpine-linux-headless-raspberrypi/releases/download/2021.06.23/headless.apkovl.tar.gz
```
Wifi Configuration (optional)
With the headless script installed. Create the wifi.txt into the boot partition: /mnt/sd/wifi.txt.
```
ssid password
```
Unmount.
```
sudo umount /mnt/sd
```

Installation

Log in into Alpine with the default username and password. If you have a headless installation you can ssh into the Raspberry Pi.
Default Alpine login credentials are username root with empty password.
Run setup.
```
setup-alpine
```
Create system partitions.
Resize the FAT32 partition to 1GB and use the remaining space to create a new primary bootable partition where Alpine Linux is gonna being installed.
```
apk add e2fsprogs
mkfs.ext4 /dev/mmcblk0p2
mount /dev/mmcblk0p2 /mnt
```
Install the system files.
```
setup-disk -m sys /mnt
```
If you get ext4 is not supported . Only supported are: vfat error, run with FORCE_BOOTFS set.
```
FORCE_BOOTFS=1 setup-disk -m sys /mnt
```
Remount old partition in RW. An update in the first partition is required for the next reboot.
```
mount -o remount,rw /media/mmcblk0p1
```
Clean up the boot folder in the first partition to drop unused files.
```
rm -f /media/mmcblk0p1/boot/*
cd /mnt
rm boot/boot
```

Move the image and init ram for Alpine Linux into the right place.

mv boot/* /media/mmcblk0p1/boot
rm -Rf boot
mkdir media/mmcblk0p1 # It's the mount point for the first partition on the next reboot

Update /etc/fstab:

echo "/dev/mmcblk0p1 /media/mmcblk0p1 vfat defaults 0 0" >> etc/fstab
sed -i '/cdrom/d' etc/fstab
sed -i '/floppy/d' etc/fstab

Enable edge repository.

sed -i '/edge/s/^#//' /mnt/etc/apk/repositories

For the next boot, indicate that the root filesystem is on the second partition. If the cmdline.txt file contains a line that starts with /root, then use sed:
```
sed -i 's/$/ root=\/dev\/mmcblk0p2 /' /media/mmcblk0p1/cmdline.txt
```

Make sure that appropriate cgroups are enabled

sed -i "s/$/ cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1/" /media/mmcblk0p1/cmdline.txt

If using chrony, allow the system clock to be stepped in the first three updates if its offset is larget than 1 second.
```
echo "makestep 1.0 3" >> /etc/chrony/chrony.conf
```
Reboot

Continue read Part 2 (Install K3s on Alpine) at Raspberry Pi K3s Alpine Linux Part 2