Assume you have a box where you run Ubuntu or your favourite distro. Now you would like to be able to boot either your already installed system or Alpine.

Prepare your hardware

You will need a partition for your Alpine installation. If you don't already have one free, you need to create a primary partition with enough space for your Alpine installation. The tools you use for managing your partitions might differ, so you need to figure out your self how to use them. fdisk can help.

Make notes of what partition you will use for your Alpine installation. In this example we are going to install Alpine on /dev/sda3.

Installing Alpine on HDD

Now it's time to install Alpine. Boot your system with a CD containing the latest Alpine Standard from Downloads.

Format and mount HDD partition

First format your partition. We will need some tools for doing the formatting. After you are done those tools can be removed.

apk add e2fsprogs mkfs.ext3 /dev/sda3 apk del e2fsprogs

Warning: Make sure you format the right partition! The /dev/sda3 is only a example. If you choose the wrong partition your data will be gone. Make a backup first when you are unsure.

Mount the newly formatted partition. After the mounting the partition will be available at /mnt.

mount -t ext3 /dev/sda3 /mnt

Basic setup

Next, do some basic setup for your Alpine system.

In Alpine 2.2.3 or newer, type:

setup-timezone setup-alpine -q setup-sshd setup-ntp

See setup-alpine for more details. (If you omit the -q flag to setup-alpine, you'll be prompted "Which disks yous you like to use?" Answer "none", and also answer "none" to the remaining prompts, about storing configs and an apk cache directory.)

Install Alpine

Now it's time to put our files on the partition.

If using Alpine Linux 2.2.3 or higher, just type:

setup-disk -m sys /mnt

Tip: If you use extlinux and you didn't create a separate boot partition (/boot is on the root partition /), you might need to update the path to vmlinuz in /boot/extlinux.conf, eg.:

[...]
LABEL hardened
  MENU DEFAULT
  MENU LABEL Linux hardened
  LINUX /boot/vmlinuz-hardened
[...]

If using an earlier version of Alpine Linux, you'll need to install the files and bootloader manually, as described below.

Installing files manually

Tip: If using a version of Alpine Linux older than 2.2.0, replace /etc/apk/world in the last line with /var/lib/apk/world

lbu package - | tar -C /mnt -xzf - apk add --root /mnt --initdb --repositories-file /etc/apk/repositores --keys-dir \ /etc/apk/keys $(cat /etc/apk/world) acct linux-hardened alpine-base

Your system is now on /dev/sda3. Next thing is to be able to boot on it.

Installing bootloader manually

On your system you already have a bootloader of some kind. The bootloaders vary, so you need to figure out how to make it boot your Alpine distro. Hopefully you get some ideas by looking at the following example below.

In my case I have Grub2 so I will describe what I did to boot Alpine.

Reboot your system (start Ubuntu).

Start a 'terminal' (ALT-F2 + "terminal" + [Run])

Take notes of the UUID of the partition you are planning to use:

sudo blkid /dev/sda3

Start editing grub2 configuration

gksudo gedit /etc/grub.d/40_custom

I edited the file so it looks something like this:

#!/bin/sh
echo "Adding Alpine" >&2
cat << EOF
menuentry "Alpine Linux" {
 set root=(hd0,3)
 linux /boot/vmlinuz-hardened root=UUID=8de6973a-4a8c-40ed-b710-c4e2b42d6b7a modules=sd-mod,usb-storage,ext3 quiet
 initrd /boot/initramfs-hardened
}
EOF

Note: The UUID-value mentioned above '8de6973a-4a8c-40ed-b710-c4e2b42d6b7a' should be replaced with the UUID you got when running your 'blkid' command.

We need to tell grub2 that the config has changed

update-grub2

Now it's time to test. Reboot your box.

Note: You might need to press SHIFT when booting up your box in order to see the grub-menu.