johnpfeiffer

Alpine Linux Introduction Tutorial

Alpine Linux is a minimalist secure linux distro.

In security terms less "footprint" often means less vectors of attack and less complexity to analyze for vulnerabilities

Alpine Linux is becoming a preferred base OS for many foundational official Docker Images (python, php, ruby, nginx, redis, haproxy, go) since downloading many large Docker Images (aka Deploying Docker Containers) can saturate the network at scale.

Getting started with Alpine Linux in Docker

This will pull the latest alpine image (around 4MB) and run it in an ephemeral container.

sudo docker run -it --rm alpine /bin/sh

Basics

Most of the very basic commands are similar to other linux distros like Debian/Ubuntu/Redhat, but of course there are differences ;)

ls -l /bin/sh

/bin/busybox

cat /etc/passwd
less /etc/passwd
vi /etc/passwd
grep root /etc/passwd
ls -l /usr/bin /usr/sbin | more

more busybox

Package Management

apk update
apk --help

update the local index for all remote packages, list the options of the package manager

apk info

list all of the packages installed locally

apk search curl
apk search curl | sort
apk info curl
apk add curl

search the remote packages for a keyword (unsorted results), get info for a specific package, install a specific package

Networking

hostname
cat /etc/resolv.conf
ifconfig
netstat -anp

traceroute
apk add iptables

Compiling C on Alpine Linux

apk add build-base gcc abuild binutils

This should probably be part of a Dockerfile rather than run every time in an ephemeral container

https://wiki.alpinelinux.org/wiki/How_to_get_regular_stuff_working#Compiling_:_a_few_notes_and_a_reminder

vi hi.c

hi.c

#include <stdio.h>

int main()
{
  printf("hi");
}

compiling

apk add file
gcc -static hi.c
chmod +x a.out
file a.out

The default is a.out: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, not stripped

./a.out

hi

Note that this was just gcc not musl-gcc :(

Incomplete musl compiler on alpine linux

WARNING: below did not work, TODO: https://bitbucket.org/GregorR/musl-cross

I suspect that I am overwriting the existing gcc toolchain and I need to specify a different prefix (/usr/local) 

apk update
apk add wget tar gzip gcc make

apk add musl-dev wget tar gzip gcc make

wget --no-check-certificate http://www.musl-libc.org/releases/musl-1.1.15.tar.gz
tar xf musl-1.1.15.tar.gz
cd musl-1.1.15
./configure
make install

Now we've installed the musl compiler?

/usr/local/musl seemed terribly empty of binaries (i.e. no /usr/local/musl/bin/)

But maybe because it's already an alpine linux container the gcc already uses musl instead of libc and does not need the musl-gcc wrapper?

http://www.guidesbyeric.com/statically-link-c-programs-with-musl-gcc

Compile Go on Alpine Linux

Just use the golang image based on alpine linux ;)

https://github.com/docker-library/docs/tree/master/golang

docker pull golang:alpine
docker run -it --rm golang:alpine /bin/sh

Now that we've got the container running we can use the shell

vi intro.go

package main

import "fmt"

func main() {
  fmt.Println("hi")
}

To just run the source code go run intro.go

hi

ls -l
go build intro.go
ls -l
./intro

hi

Maybe

http://dominik.honnef.co/posts/2015/06/go-musl/ ?

Git with Alpine

apk update
apk add --no-cache git
git --version

Published

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linux

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