Set up Alpine Linux RAID1 over 4 disks with 16GB rootfs size

gistfile1.txt

# set up basic alpine environment (networking, kbd layout, apk repo)
setup-alpine -q

# add some required packages
apk add e2fsprogs mdadm parted sgdisk gptfdisk

# create partition layout on the first disk
gdisk /dev/sda
> o
> y
> n
>
>
> +128M
> fd00
> n
>
>
> +16G
> fd00
> w
> y

# copy the partition layout to all other disks
sgdisk /dev/sda -R /dev/sdb
sgdisk /dev/sda -R /dev/sdc
sgdisk /dev/sda -R /dev/sgd

# randomize the UUIDs on all the disks
sgdisk -G /dev/sdb
sgdisk -G /dev/sdc
sgdisk -G /dev/sdd

# set the bootable flag on the first partition of all disks
# Note: I'm not sure if this is being copied by the sgdisk -R command above,
#       so to be 100% sure, we set it manually on all disks
sgdisk /dev/sda --attributes=1:set:2
sgdisk /dev/sdb --attributes=1:set:2
sgdisk /dev/sdc --attributes=1:set:2
sgdisk /dev/sdd --attributes=1:set:2

# create our /boot raid1
# Note: --metadata 1.0 is VERY important here, syslinux does not support anything newer!
mdadm --create /dev/md0 --metadata 1.0 -l 1 -n 4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1

# create our / raid1
mdadm --create /dev/md1 -l 1 -n 4 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2

# create ext4 partitions
mkfs.ext4 -m 0 /dev/md0
mkfs.ext4 /dev/md1

# mount the partitions
mount -t ext4 /dev/md1 /mnt
mkdir /mnt/boot /mnt/etc
mount -t ext4 /dev/md0 /mnt/boot

# write the mdadm config so we don't end up with md127/md126 instead of md0/md1
mdadm --detail --scan > /mnt/etc/mdadm.conf

# make sure we include the raid1 module in our initrd
echo raid1 >> /etc/modules

# do the actual alpine linux installation
setup-disk -m sys /mnt

# cleanly unmount everything
umount /mnt/boot /mnt

# write the GPT/MBR bootloader to the disk protective mbr
dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sda
dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sdb
dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sdc
dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sdd

# make sure all disks are synced before rebooting/shutting down
sync