How to make a custom ISO image with mkimage

2024-06-11T03:48:38Z

Jeffre: fix path as referenced earlier

This document explains how to build a custom ISO image using the new mkimage scripts located in [[aports]] directory.

== Prerequisites ==

First make sure we have the needed tools
{{Cmd|apk add alpine-sdk alpine-conf syslinux xorriso squashfs-tools grub grub-efi doas}}
For efi you should add the following:
{{Cmd|apk add mtools dosfstools grub-efi}}

Create a user (e.g. build) and add them to the abuild group:
{{Cmd|adduser build -G abuild}}

Give the user root-like permissions:
{{Cmd|vi /etc/doas.d/doas.conf}}
<pre>
permit :abuild
permit persist :abuild
</pre>

Change to the build user:
{{Cmd|su - build}}

Then create signing keys (-i installs them in /etc/apk/keys which is required for later)
{{Cmd|abuild-keygen -i -a}}

{{Tip| Make sure your public keys are placed in /etc/apk/keys/ (example: build-xxxxxxxx.rsa.pub)}}
{{Cmd|ls /etc/apk/keys/}}

Clone (or update) the [https://gitlab.alpinelinux.org/alpine/aports git repository].
{{Cmd|git clone --depth=1 https://gitlab.alpinelinux.org/alpine/aports.git}}

Make sure the apk index is up to date (so apk can find the packages):
{{Cmd|doas apk update}}

Make sure your /tmp is large enough. If you have the default 1GB /tmp, then create a local one with:
<pre>mkdir -pv ~/tmp
export TMPDIR=~/tmp</pre>

== Configuration ==

The mkimg scripts are shipped with pre-configured profiles.

The format is '''mkimg.$PROFILENAME.sh'''

In order to have a custom ISO, you should create your own '''mkimg.$PROFILENAME.sh''' script.

This is an example used to make a ZFS module, overlayfs (which enables r/w mode for /lib/modules), a serial console output and some other useful apks to build a simple NAS:

<pre>export PROFILENAME=nas</pre>

<pre>
cat << EOF > ~/aports/scripts/mkimg.$PROFILENAME.sh
profile_$PROFILENAME() {
profile_standard
kernel_cmdline="unionfs_size=512M console=tty0 console=ttyS0,115200"
syslinux_serial="0 115200"
kernel_addons="zfs"
apks="\$apks iscsi-scst zfs-scripts zfs zfs-utils-py
cciss_vol_status lvm2 mdadm mkinitfs mtools nfs-utils
parted rsync sfdisk syslinux util-linux xfsprogs
dosfstools ntfs-3g
"
local _k _a
for _k in \$kernel_flavors; do
apks="\$apks linux-\$_k"
for _a in \$kernel_addons; do
apks="\$apks \$_a-\$_k"
done
done
apks="\$apks linux-firmware"
}
EOF
</pre>

Set the script as executable:
{{Cmd|chmod +x ~/aports/scripts/mkimg.$PROFILENAME.sh}}

== Making packages available on boot ==

A package may be made available in the live system by defining the generation of an apkovl which contains a corresponding /etc/apk/world file, and adding that overlay definition to the mkimg-profile, e.g. with `apkovl="genapkovl-mkimgoverlay.sh"`

Note that to *use* your added apks, you have to install them, with {{ic|apk add}}.

The definition may be done as in the [https://github.com/alpinelinux/aports/blob/master/scripts/genapkovl-dhcp.sh genapkovl-dhcp.sh] example.
Copy the relevant parts (including the rc_add lines) into a `genapkovl-mkimgoverlay.sh` file and add the package(s) that should be installed in the live system on separate lines in the file contents for /etc/apk/world.

{{Cmd|cp ~/aports/scripts/genapkovl-dhcp.sh ~/aports/scripts/genapkovl-mkimgoverlay.sh}}

Edit the file to add:
<pre>
...
mkdir -p "$tmp"/etc/apk
makefile root:root 0644 "$tmp"/etc/apk/world <<EOF
alpine-base
<apk1-service>
<apk2-service>
EOF

...
rc_add <apk1-service> boot
rc_add <apk2-service> boot
...
</pre>

in the relevant locations.

Then edit the profile build script above and add:
<pre>
apkovl="aports/scripts/genapkovl-mkimgoverlay.sh"
</pre>

immediately after the last apks= line.

== Create the ISO ==

{{Cmd|mkimage.sh [--tag RELEASE] [--outdir OUTDIR] [--workdir WORKDIR]
[--arch ARCH] [--profile PROFILE] [--hostkeys] [--simulate]
[--repository REPO] [--extra-repository REPO] [--yaml FILE]
mkimage.sh --help

options:
--arch Specify which architecture images to build
(default: x86_64)
--hostkeys Copy system apk signing keys to created images
--outdir Specify directory for the created images
--profile Specify which profiles to build
--repository Package repository to use for the image create
--extra-repository Add repository to search packages from
--simulate Don't execute commands
--tag Build images for tag RELEASE
--workdir Specify temporary working directory (cache)
--yaml

known profiles: ali rpi uboot base minirootfs standard vanilla extended virt xen}}

{{Tip| You can use the --repository option multiple times, which is very useful when mixing local and official repositories. The --extra-repository option is there only for backward-compatibility.}}

Create an iso directory in your home dir:

{{Cmd|mkdir -p ~/iso}}

Then create the actual ISO.
In this example we will use the edge version x86_64:
{{Cmd|sh aports/scripts/mkimage.sh --tag edge \
--outdir ~/iso \
--arch x86_64 \
--repository <nowiki>https://dl-cdn.alpinelinux.org/alpine/edge/main</nowiki> \
--profile $PROFILENAME
}}

'''Notes:'''

* If you want to make a customized installer, you need to create <code>.default_boot_services</code> which will cause <code>mkinitfs</code> to create the defaults for the live image.

* Several parts of this doc can be automated with a script, like the repository/arch/outdir settings.
Those steps are left to you and your imagination :)

== Testing your ISO image ==

[[QEMU#Live_mode|QEMU]] is useful for a quick test of your newly created ISO image.
This ISO build process has been tested to work and generate an ISO with auto-installed APKs as of Nov 20, 2023 with Alpine edge.

[[Category:Package Manager]]
[[Category:ISO]]

Alpine Linux - User contributions [en]

How to make a custom ISO image with mkimage