FAQ collection for building custom images

[fwilhe]

The purpose of this issue is to collect FAQ regarding the builder. Eventually, they should end up in documentation or automation where possible.

Q: My image's partitions are too small, how to make them bigger?

A: One option is to edit fstab in the base feature like in this example

# <file system>    <dir>        <type>    <options>                                <makeimg args>
LABEL=EFI          /boot/efi    vfat      umask=0077                               type=uefi,size=512MiB
LABEL=ROOT         /            ext4      rw,errors=remount-ro,prjquota,discard    size=4GiB

Adapt the size arguments as needed

Q: I'm trying to download something in a builder feature but it fails because the hostname can't be resolved

A: Resolv conf needs to be configured. You may add a feature networking with the following scripts and include that in your build

exec.early:

#!/usr/bin/env bash

set -eufo pipefail

mkdir -p /run/systemd/resolve/
cp /etc/resolv.conf /run/systemd/resolve/stub-resolv.conf

exec.post:

#!/usr/bin/env bash

set -eufo pipefail

rootfs="$1"

rm "$rootfs/etc/hostname"
echo -n > "$rootfs/etc/hostname"

rm "$rootfs/etc/resolv.conf"
ln -s /run/systemd/resolve/resolv.conf "$rootfs/etc/resolv.conf"

Q: My image only has the root user. How do I create non-privileged user to work with?

A: Create a user feature with a exec.config file like this:

useradd --user-group --create-home --shell=/usr/bin/bash --password="$(openssl passwd -6 user)" user

This will create a user named user with password user.
You might want to read the password from a file or environment variable which are not checked into version control.

Q: My user should be able to use sudo for admin purposes.

A: Create a file in your user feature file.include/etc/sudoers.d/USERNAME, with this contents: USERNAME ALL=(ALL) NOPASSWD: ALL

Q: How can I use ssh to work with the machine?

A: