View source for Alpine Linux:Overview

Alpine uses [https://musl.libc.org/ 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 [https://musl.libc.org/ 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:

# Usage of [https://musl.libc.org/ musl] as the minimalist libc
# Its own package manager called [[Alpine Package Keeper|apk]], 
# The {{Pkg|openrc}} init system, script driven set-ups and that’s it!
# {{Pkg|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 ==

<ol>
<li>'''Architectures'''

<p>Alpine uses '''Linux''' as [https://www.kernel.org/ OS kernel], and has a focus on '''SSS distribution, Simple Small and Secure'''</p>

<p>A variety of architectures are officially supported:
* '''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.


</li><li>'''Installing'''

<p>Alpine can be installed to a hard disk/SSD/other storage medium like any other distro (this is called '''sys mode'''). The storage medium in question can be any block device (USB, Flash, SDD, HDD). It can be removable, so long as you can configure your machine to boot from it. But if you're working with removable media, you might prefer one of the other installation modes.</p>

<p>In each of these modes, you boot your machine from a static image. You will also need a writable medium to save updates to the system. In '''diskless mode''', that medium is usually a small USB key (or a partition on one) that holds the changes you want to persist. Both the base Alpine system and all your changes will be unpacked into a memory-based filesystem.</p>

<p>The other, '''data''' mode is for when you're dealing with a large amount of persisting data, that you want to keep on a hard disk/SSD/other storage medium, rather than unpacking into memory. The default setup here is to store your {{Path|/var}} partition directly on the hard storage medium. But as in the '''diskless''' mode, your root system still comes from a static ISO image.</p>

<p>These second and third installation modes are sometimes referred to, collectively, as "run-from-RAM" installations.</p>

<p>Key to these installation modes is Alpine's [[Alpine local backup|lbu]] utility. This tracks which files you've modified from their static ISO version, and want the changes to persist. The lbu utility saves those changes in {{Path|.apkovl}} "overlay" files. (These are essentially tar-gzip archives, though they can also be encrypted. You can use the lbu utility with the '''sys''' mode, too, if you like: as a form of backup, or to configure overlay files for other systems. But for a robust incremental backup system, you'll probably want a more specialized tool, such as {{Pkg|rsnapshot}}.)</p>

<p>The lbu utility is part of the {{Pkg|alpine-conf}} package, which is required by {{Pkg|alpine-base}}.</p>


<p>'''Alpine's installer''' consists of '''the {{Path|/sbin/setup-*}} scripts''', which are also part of the {{Pkg|alpine-conf}} package.

</p><p>'''A base Alpine install will include only needed packages''' such like {{Pkg|alpine-base}}, {{Pkg|syslinux}}, {{Pkg|linux-lts}} (or another kernel package), and depending on your purposes packages like {{Pkg|openssh}} and/or {{Pkg|chrony}}.

</p><p>Alpine's boot loader in that case is {{Pkg|syslinux}}, or its companions <code>isolinux</code> or <code>extlinux</code>. The latest releases also have Grub and [[Alpine and UEFI|UEFI support]].</p>

</li><li>'''The init system'''

<p>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 {{Path|/sbin/mkinitfs}}, part of the {{Pkg|mkinitfs}} package, which is required by Alpine's kernel packages and by its {{Pkg|syslinux}} package. This tool's settings are read from {{Path|/etc/mkinitfs/*}}, and it installs the initscript {{Path|/usr/share/mkinitfs/initramfs-init}} into the initramfs.

</p><p>Second, Alpine uses [[Alpine Linux Init System|OpenRC]] to handle the rest of its initscripts. The base framework of this is in the {{Pkg|openrc}} package, which is required by {{Pkg|alpine-conf}}.
</p>

</li><li>'''The packaging and development system'''

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

</p><p>In Alpine's case, these are something a hybrid between [https://www.archlinux.org/ ArchLinux]'s, on the one hand, and [https://www.gentoo.org/ Gentoo] and [https://www.freebsd.org/ FreeBSD]'s, on the other. Our package-management and build utilities work much like Arch's:

* {{Pkg|mkinitfs}}, mentioned above, rebuilds Alpine's initramfs, like Arch's "mkinitcpio"
* '''apk''' from {{Pkg|apk-tools}} is Alpine's package manager, like Arch's "pacman"; see [[Alpine Linux package management]]
* {{Pkg|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"

</p><p>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.)

</p><p>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 {{Pkg|mkinitfs}} and {{Pkg|apk-tools}}, both included in a base Alpine install. If you do plan to do development, install {{Pkg|alpine-sdk}}, which includes gcc, git, abuild, and the like, and see [[Developer Documentation]].
</p>

</li></ol>

= See Also =

* [[Comparison with other distros]]
* [[Tutorials and Howtos]]
* [https://en.wikipedia.org/wiki/BusyBox BusyBox]

[[Category:Installation]]