Not today... - Alpine on a Raspberry

Sun Jan 5 2020

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Alpine on a Raspberry

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Lately, I decided to re-install my old Raspberry Pi (version 1, yes I’m that old) to create a small home server. Since I am using Alpine and liking it quite a lot, I wanted to install it on my new little toy project.

I followed documentations and tutorials ( here and here) and finally succeeded. I am now writing it down so I remember what has been achieved.

Setup SD Card

This one was quite tricky because if anything is not exactly what is expected your raspberry will never boot! I am copy-pasting here the commands executed to properly setup the SD card partitions (I took the fdisk automation from this stack overflow answer):

# replace /dev/...  with your sdcard entry
sed -e 's/\s*\([\+0-9a-zA-Z]*\).*/\1/' << EOF | fdisk /dev/mmcblk0
  o # clear the in memory partition table
  n # new partition
  p # primary partition
  1 # partition number 1
    # default - start at beginning of disk
  +256M # 256 MB boot parttion
  n # new partition
  p # primary partition
  2 # partion number 2
    # default, start immediately after preceding partition
    # default, extend partition to end of disk
  t # change partition type
  1 # for partition 1
  c # partition type is W95 FAT32 (LBA)
  p # print the in-memory partition table
  w # write the partition table
  q # and we're done
EOF

# here as well replace with proper path (lsblk will help you)
mkfs.vfat /dev/mmcblk0p1
mkfs.ext4 /dev/mmcblk0p2

Now, we have to run some commands because the raspberry I am using need so.

cd $(mktemp -d) && mount /dev/mmcblk0p1 . && cd .
curl -o - http://dl-cdn.alpinelinux.org/alpine/v3.11/releases/armhf/alpine-rpi-3.11.2-armhf.tar.gz | \
	tar xzf -
rm boot/*-rpi2
mv boot/* .

cat > config.txt <<-EOF
	disable_splash=0
	boot_delay=0
	gpu_mem=256
	gpu_mem_256=32
	kernel=vmlinuz-rpi
	initramfs initramfs-rpi
EOF

Once this is done, the SD card is ready to be plugged and the Raspberry to be booted.

First boot and in-memory setup

When the booting is done, you will get a prompt, user is root and no password should be required.

# run the setup and answer the various questions
setup-alpine

# be sure to have properly installed ssh as it ease the administration,
# we now create a user to be able to connect in
adduser -G wheel foo

# the clock may display some errors, better fix it
ntpd -q -p ptbtime1.ptb.de

# we can now commit the changes
lbu commit -d
# if you want reboot in order to ensure that changes are properly saved
reboot

Doing the persistent install

The sys install is the next phase, it will allow your installation to survive reboots (as you would expect from a regular machine).

# we mount the ext4 partition
cd $(mktemp -d) && mount /dev/mmcblk0p2 . && cd .

# we copy from the previous commited image (you can ignore the syslinux/extlinux errors)
setup-disk -o /media/mmcblk0p1/MYHOSTNAME.apkovl.tar.gz $(pwd)

# now we update the fstab
echo "/dev/mmcblk0p1 /media/mmcblk0p1 vfat defaults 0 0" >> ./etc/fstab

We now need to change the boot partition a bit in order to switch to our newly installed system.

mount -o remount,rw /media/mmcblk0p1 && cd media/mmcblk0p1
sed -i '$ s/^/root=\/dev\/mmcblk0p2 /' /media/mmcblk0p1/cmdline.txt

mkdir kernel-installer
mv System.map-rpi config-rpi initramfs-rpi vmlinuz-rpi kernel-installer
cd - && cp -v ./boot/* /media/mmcblk0p1

Everything should now works on next boot! You have successfully installed Alpine on a Raspberry!