Architecture

Packaging

Alpine uses packages in the .apk file format.

Package Management Tools

• apk

Package Building Tools

• abuild

Boot Process

Kernel

Versioning

Flavors

• vanilla
• hardened
• virthardened
• rpi

Initfs

The kernel will decompress the stream of compressed cpio archives passed to it by the 'append' bootloader option to the root of 'rootfs', a tmpfs automatically mounted at '/' by the kernel at boot.

'/init' Script

Not to be confused with '/sbin/init', the '/init' script in the root of the 'rootfs' is called by the kernel upon completion of its boot process, and is responsible for doing whatever steps are necessary to mount the real root file system to '/' and transfer control to '/sbin/init'.

Minimal Required Set

Directory Structure

• / /bin /boot /dev /etc /lib /lib/modules /media /media/cdrom /media/usb /mnt /proc /sbin /sys /usr /usr/bin /usr/sbin

Devices

• /dev/null
• /dev/console
• /dev/kmsg

Mounts

• /proc
• /sys
• /dev (can be disabled?)

Configuration

• /etc/passwd
• /etc/group
• /etc/fstab

Binaries

• busybox
• apk

Feature Sets

Feature sets consist of lists for the set of modules and files that need to be included in a final initramfs to support the indicated feature.

Init

Not to be confused with the '/init' script in the initramfs, '/sbin/init' is the first process to be started in the live system after the initramfs completes its work.