path: root/content/blog/2022-10-22-alpine-linux.org

#+date:        [2022-10-22 Sat 00:00:00]
#+title:       Alpine Linux: Minimal Install, Minimal Attack Surface
#+description: Installing Alpine Linux as a lightweight, secure server OS.
#+slug:        alpine-linux
#+filetags:    :linux:

* Alpine Linux

[[https://alpinelinux.org][Alpine Linux]] is a very small distribution, built on musl libc and busybox. It
uses ash as the default shell, OpenRC as the init system, and apk as the package
manager. According to their website, an Alpine container "requires no more than
8 megabytes (MB) and a minimal installation to disk requires around 130 MB of
storage." An actual bare metal machine is recommended to have 100 MB of RAM and
0-700 MB of storage space.

Historically, I've used Ubuntu's minimal installation image as my server OS for
the last five years. Ubuntu worked well and helped as my original server
contained an nVidia GPU (graphics processing unit) and no onboard graphics, so
quite a few distributions won't boot or install without a lot of tinkering.

Alpine has given me a huge increase in performance across my Docker apps and
Nginx websites. CPU (central processing unit) load for the new server I'm using
to test Alpine hovers around 0-5% on average with an Intel(R) Core(TM) i3-6100
CPU @ 3.70 Gigahertz (GHz).

The only services I haven't moved over to Alpine are Plex Media Server and
Syncthing, which may increase CPU load quite a bit depending on how many streams
are running.

** Installation

In terms of installation, Alpine has an incredibly useful [[https://wiki.alpinelinux.org/wiki/Installation][wiki]] that will guide a
user throughout the installation and post-installation processes, as well as
various other articles and guides.

To install Alpine, find an appropriate [[https://alpinelinux.org/downloads/][image to download]] and flash it to a USB
(Universal Serial Bus) using software such as Rufus or Etcher. I opted to use
the Standard image for my x86_{64} architecture.

Once the USB is ready, plug it into the machine and reboot. Note that you may
have to use a key such as =Esc= or =F1-12= to access the boot menu. The Alpine
Linux terminal will load quickly and for a login.

To log in to the installation image, use the =root= account; there is no
password. Once logged-in, execute the setup command:

#+begin_src sh
setup-alpine
#+end_src

The setup script will ask a series of questions to configure the system. Be sure
to answer carefully or else you may have to re-configure the system after boot.

- *Keyboard Layout*: Local keyboard language and usage mode, e.g., us and variant
  of us-nodeadkeys.
- *Hostname*: The name for the computer.
- *Network*: For example, automatic internet protocol (IP) address discovery
  with the Dynamic Host Configuration Protocol (DHCP) protocol.
- *DNS (Domain Name System)*: DNS servers to query. For privacy reasons, it is
  NOT recommended to route every local request to servers like Google's
  8.8.8.8.
- *Timezone
- *Proxy*: Proxy server to use for accessing the web. Use =none= for direct
  connections to the internet.
- *Mirror*: From where to download packages. Choose the organization you trust
  giving your usage patterns to.
- *SSH (Secure Shell Protocol)*: Remote access server. =Openssh= is part of the
  default install image. Use =none= to disable remote login, e.g. on laptops.
- *NTP (Network Time Protocol)*: Client used for keeping the system clock in
  sync with a time-server. Package =chrony= is part of the default install
  image.
- *Disk Mode*: Select between diskless (=none=), =data= or =sys=, as described
  above.

Once the setup script is finished, be sure to reboot the machine and remove the
USB device.

#+begin_src sh
reboot
#+end_src

** Post-Installation

There are many things you can do once your Alpine Linux system is up and
running, and it largely depends on what you'll use the machine for. I'm going to
walk through my personal post-installation setup for my web server.

1. Upgrade the System

   First, login as =root= in order to update and upgrade the system:

   #+begin_src sh
   apk -U upgrade
   #+end_src

2. Adding a User

   I needed to add a user so that I don't need to log in as root. Note that if
   you're used to using the =sudo= command, you will now need to use the =doas=
   command on Alpine Linux.

   #+begin_src sh
   apk add doas
   adduser <username>
   adduser <username> wheel
   #+end_src

   You can now log out and log back in using the newly-created user:

   #+begin_src sh
   exit
   #+end_src

3. Enable Community Packages

   In order to install more common packages that aren't found in the =main=
   repository, you will need to enable the =community= repository:

   #+begin_src sh
   doas nano /etc/apk/repositories
   #+end_src

   Uncomment the community line for whichever version of Alpine you're running:

   #+begin_src sh
   /media/usb/apks
   http://dl-cdn.alpinelinux.org/alpine/v3.16/main
   http://dl-cdn.alpinelinux.org/alpine/v3.16/community
   #http://dl-cdn.alpinelinux.org/alpine/edge/main
   #http://dl-cdn.alpinelinux.org/alpine/edge/community
   #http://dl-cdn.alpinelinux.org/alpine/edge/testing
   #+end_src

4. Install Required Packages

   Now that the community packages are available, you can install any packages
   you need. In my case, I installed the web server packages I need for my
   services:

   #+begin_src sh
   doas apk add nano nginx docker docker-compose ufw
   #+end_src

5. SSH

   If you didn't install OpenSSH as part of the installation, you can do so now:

   #+begin_src sh
   doas apk add openssh
   #+end_src

   Next, either create a new key or copy your SSH key to the server from your
   current machines:

   #+begin_src sh
   # Create a new key
   ssh-keygen
   #+end_src

   If you need to copy an existing SSH key from a current machine:

   #+begin_src sh
   # Copy key from existing machines
   ssh-copy-id <username>@<ip_address>
   #+end_src

6. Firewall

   Lastly, I installed =ufw= above as my firewall. To set up, default to deny
   incoming and allow outgoing connections. Then selectively allow other ports
   or apps as needed.

   #+begin_src sh
   doas ufw default deny incoming
   doas ufw default allow outgoing
   doas ufw allow SSH
   doas ufw allow "WWW Full"
   doas ufw allow 9418 # Git server port
   #+end_src

7. Change Hostname

   If you don't like the hostname set during installation, you just need to edit
   two files. First, edit the simple hostname file:

   #+begin_src sh
   doas nano /etc/hostname
   #+end_src

   #+begin_src sh
   <hostname>
   #+end_src

   Next, edit the =hosts= file:

   #+begin_src sh
   doas nano /etc/hosts
   #+end_src

   #+begin_src sh
   127.0.0.1   <hostname>.local <hostname> localhost.local localhost
   ::1         <hostname> <hostname>.local
   #+end_src

* Nginx Web Server

To set up my web server, I simply created the =www= user and created the
necessary files.

#+begin_src sh
doas adduser -D -g 'www' www
mkdir /www
doas mkdir /www
doas chown -R www:www /var/lib/nginx/
doas chown -R www:www /www
#+end_src

If you're running a simple webroot, you can alter the main =nginx.conf= file.
Otherwise, you can drop configuration files in the following directory. You
don't need to enable or symlink the configuration file like you do in other
systems.

#+begin_src sh
doas nano /etc/nginx/http.d/example_website.conf
#+end_src

Once the configuration is set and pointed at the =/www= directory to serve
files, enable the Nginx service:

#+begin_src sh
# Note that 'default' must be included or Nginx will not start on boot
doas rc-update add nginx default
#+end_src

* Docker Containers

Docker works exactly the same as other systems. Either execute a =docker run=
command or create a =docker-compose.yml= file and do =docker-compose up -d=.

* Git Server

I went in-depth on how to self-host a git server in another post: [[https://cleberg.net/blog/git-server.html][Self-Hosting
Guide: Git & cGit]].

However, there are a few differences with Alpine. First note that in order to
change the =git= user's shell, you must do a few things a little different:

#+begin_src sh
doas apk add libuser
doas touch /etc/login.defs
doas mkdir /etc/default
doas touch /etc/default/useradd
doas lchsh git
#+end_src

* Thoughts on Alpine

So far, I love Alpine Linux. I have no complaints about anything at this point,
but I'm not completely finished with the migration yet. Once I'm able to upgrade
my hardware to a rack-mounted server, I will migrate Plex and Syncthing over to
Alpine as well - possibly putting Plex into a container or VM.

The performance is stellar, the =apk= package manager is seamless, and system
administration tasks are effortless. My only regret is that I didn't install
Alpine sooner.