alpine-make-rootfs/README.adoc

= Make Alpine Linux RootFS
:script-name: alpine-make-rootfs
:script-sha1: 2ebf310a0c6eb1b3ac9587d6211f1e84227846f0
:gh-name: alpinelinux/{script-name}
:version: 0.7.2

ifdef::env-github[]
image:https://github.com/{gh-name}/workflows/CI/badge.svg["Build Status", link="https://github.com/{gh-name}/actions"]
endif::env-github[]

This project provides a script for building customized https://alpinelinux.org/[Alpine Linux] rootfs (a base image if you like) for containers.
It’s quite simple (300 LoC of shell), fast and requires minimum dependencies (just common Linux tools).

TIP: Do you want to just quickly chroot into Alpine Linux, e.g. on CI?
     Check out https://github.com/alpinelinux/alpine-chroot-install[alpine-chroot-install]!


== Requirements

* Linux system
* http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html[POSIX-sh] compatible shell (e.g. Busybox ash, dash, ZSH, bash, …)
* common userland with `chroot`, `getopt`, `grep`, `sed`, `sha256sum`, `wget` (e.g. from Busybox, GNU coreutils, …)
* `tar` (full-blown)


== Usage

Read documentation in link:{script-name}[{script-name}].
See link:.github/workflows/ci.yml[] for GitHub Actions example.

You can copy link:{script-name}[{script-name}] into your repository or download it on demand, e.g.:

[source, sh, subs="+attributes"]
wget https://raw.githubusercontent.com/{gh-name}/v{version}/{script-name} \
    && echo '{script-sha1}  {script-name}' | sha1sum -c \
    || exit 1


== Examples

=== Installation Script in Heredoc

[source, sh]
----
sudo ./alpine-make-rootfs \  # <1>
    --branch v3.8 \  # <2>
    --packages 'ruby ruby-bigdecimal sqlite' \  # <3>
    --timezone 'Europe/Prague' \  # <4>
    --script-chroot \  # <5>
    example-$(date +%Y%m%d).tar.gz - <<'SHELL'  # <6>
        # Copy some file from the repository root to the rootfs.
        install -D -m 755 examples/hello_world.rb /app/hello_world.rb

        # Install some dev packages and gem mailcatcher.
        apk add --no-progress -t .make build-base ruby-dev sqlite-dev
        gem install --no-document mailcatcher

        # Clean-up dev packages.  <7>
        apk del --no-progress .make
SHELL
----
<1> The script needs to create files owned by _root_ or other users and optionally uses chroot (when `--script-chroot` is specified), so it must be run under _root_ (e.g. using `sudo`).
<2> Alpine branch (release) to install (see https://wiki.alpinelinux.org/wiki/Alpine_Linux:Releases[Alpine Releases]).
<3> You can name packages to install into the chroot, in addition to base packages (see `ALPINE_BASE_PKGS` in link:{script-name}[{script-name}]).
<4> You may specify timezone to set (default is UTC).
<5> This flag tells that the installation script will be executed inside chroot with the rootfs as new root.
    Your current working directory is binded at `/mnt` inside the chroot and `$PWD` for the script is set to `/mnt`, so you can easily access files out of the chroot and copy them into the rootfs.
<6> Installation script may be provided also via STDIN, using a convenient heredoc syntax.
    The script passed is executed using `/bin/sh -e`.
<7> Note that it’s not needed to clean `apk` cache, this is done automatically.


=== Create Docker Base Image

Create your own (customized) up-to-date base image.

[source, sh]
----
sudo ./alpine-make-rootfs --branch v3.8 - | docker import -c 'CMD /bin/sh' - my/alpine:3.8
----


=== Create OCI Image

You can use simply shell script https://github.com/jirutka/sloci-image/[sloci-image] to pack the generated rootfs as a single-layer OCI image.

[source, sh]
----
sudo ./alpine-make-rootfs --branch v3.8 --script-chroot rootfs.tar.gz ./install.sh
./sloci-image --entrypoint /start.sh --port 80/tcp --tar rootfs.tar.gz alpine:3.8
----


== License

This project is licensed under http://opensource.org/licenses/MIT/[MIT License].
For the full text of the license, see the link:LICENSE[LICENSE] file.