Dualbooting

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.

For this, see: Manual_partitioning

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

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.ext4 /dev/sdXY apk del e2fsprogs

Warning: Make sure you format the right partition! The /dev/sdXY 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 ext4 /dev/sdXY /mnt

Basic setup

This sets up alpine without installing to any disk, yet.

To do this, either run

setup-alpine

, and when to prompted "Which disks do you like to use?" make sure to answer "none", and also answer "none" to the remaining prompts, about storing configs and the apk cache directory.

Alternatively, run this command selection:

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

See setup-alpine for more details.

Install Alpine

Now it's time to copy the prepared system to the prepared partition(s) that where mounted below /mnt.

In Alpine 2.2.3 or newer

setup-disk -m sys /mnt

Tip: If you use extlinux (default) and didn't create a separate boot partition, i.e. (/boot resides on the root partition /), you might need to adjust the paths to the boot files in /boot/extlinux.conf, eg.:

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

Check that the LINUX and INITRD paths actually point to the files shipped in your Alpine Linux release.

With older Alpine versions up to 2.2.3

If using an earlier version of Alpine Linux, you'll need to install the files and bootloader 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/repositories --keys-dir \ /etc/apk/keys $(cat /etc/apk/world) acct linux-hardened alpine-base

Your system is now on /dev/sdXY.

Configuring the bootloader

Bootloaders

There are different ways to get a boot menu that allows selecting the operating system to boot.

It is easiest probably on (U)EFI based hardware platforms, where one may simply install the rEFInd boot menu, as explained in Bootloaders.

Otherwise, one may adjust the bootloader that has already been installed (by the other operating system).

Because the different bootloaders vary, you need to figure out how to make yours boot your Alpine instsall.

Hopefully you can get some ideas from the following example, adjusting Grub2 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/sdXY

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,ext4 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.