Alpine Linux:Overview

Alpine uses musl as its libc, and BusyBox as core utilities. These choices tend to make Alpine especially minimalist and secure.

General overview

Alpine Linux has one of the fastest boot times of any operating system.

It's famous because of its small size and it's heavily used in containers.

It's also well known for wide use in embedded devices and as a base system for many enterprise routers.

The postmarketOS project, which is designed to run on mobile devices, is based on Alpine Linux.

Distinctive

Alpine Linux follows the principles of the SSS distro: Simple+Small+Secure: due to usage of muslc as the minimalist libc, BusyBox simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also) and userland binaries compiled as Position Independent Executables (PIE) with stack smashing protection.

Efficient

Some main reasons:

1. Usage of musl as the minimalist libc
2. Its own package manager called apk,
3. The openrc init system, script driven set-ups and that’s it!
4. busybox: simple coreutils (with possibilities to alternate on inflated original packages of each coreutils tools also)

This provides you with a simple, crystal-clear Linux environment without all the noise, nothing else will get in the way.

Secure

All userland binaries are compiled as Position Independent Executables (PIE) with stack smashing protection.

Technical overview

1. The OS design

   Alpine uses Linux as OS kernel, and has a focus on SSS distribution, Simple Small and Secure

   A variety of architectures are officially supports:

   • x86_64: The popular AMD64 compatible 64-bit x86 based machines, i386 are not recommended for newer/latest hardware.
   • x86: (i386 pc 32bit) and x86_64 (i686 pc 64bit and amd64)
   • armhf: The newer ARM hard-float for newer, more powerful 32-bit devices alongside 64-bit
   • armv7: The 32-bit ARM only execution state of the ARMv7 devices machines.
   • aarch64: The 64-bit ARM only execution state of the ARMv8 device machines.
   • ppc64le: For 64-bit PowerPC devices with pure little-endian mode, mostly for POWER8 and POWER9.
   • s390x: For IBM Z mainframes, especially IBM Z and IBM LinuxONE.

   Alpine can be installed to a hard disk/SSD/other storage medium like any other distro; (sys mode). The storage medium in question can be any block device (USB, Flash, SDD, HDD). Always in start, the base Alpine system and all your changes will be unpacked into a memory-based filesystem. If run some install script process (data mode) will keep your setup on a hard disk/SSD/other storage medium, rather than unpacking into memory. The default setup here is to store your /var partition directly on the hard storage medium. But as in the diskless mode, your root system still comes from a static ISO image.

2. The installation

   In Alpine's case, the installer consists of the /sbin/setup-* scripts, which are also part of the alpine-conf package.

   A base Alpine install will include only needed packages such like alpine-base, syslinux, linux-lts (or another kernel package), and depending of purpose some like openssh/chrony.

   Alpine's boot loader case this is syslinux, or its companions isolinux or extlinux. Latest releases have Grub and UEFI support.

3. The init system

   An "init system" includes several different components. First, there is the initramfs, which is loaded by the bootloader. Alpine's tool for generating the initramfs is /sbin/mkinitfs, part of the mkinitfs package, which is required by Alpine's kernel packages and by its syslinux package. This tool's settings are read from /etc/mkinitfs/*, and it installs the initscript /usr/share/mkinitfs/initramfs-init into the initramfs.

   Second, Alpine uses OpenRC to handle the rest of its initscripts. The base framework of this is in the openrc package, which is required by alpine-conf.

4. The packaging and development system

   The last important distinguishing feature of a Linux distro is its packaging and development systems.

   In Alpine's case, these are something a hybrid between ArchLinux's, on the one hand, and Gentoo and FreeBSD's, on the other. Our package-management and build utilities work much like Arch's:

   • mkinitfs, mentioned above, rebuilds Alpine's initramfs, like Arch's "mkinitcpio"
   • apk from apk-tools is Alpine's package manager, like Arch's "pacman"; see Alpine Linux package management
   • abuild is Alpine's build utility, like Arch's "makepkg"; see Abuild and Helpers
   • Alpine's package-building scripts are named APKBUILD, like Arch's "PKGBUILD"

   What Alpine borrows from Gentoo and FreeBSD is a tree of all the package-building scripts. It is called the Aports tree, and is kept as a single git repository. (Compare Gentoo's "Portage" and FreeBSD's "ports". Something similar can be set up with Arch's "abs", but it's not as tightly integrated with their package manager and build utilities.)

   If you're only planning to install packages on a given system, and not do any development there, then the only pieces of this you'll need are mkinitfs and apk-tools, both included in a base Alpine install. If you do plan to do development, install alpine-sdk, which includes gcc, git, abuild, and the like, and see Developer Documentation.

See Also

• Comparison with other distros
• Tutorials and Howtos