Why I Use the Debian Expert Install

A Hidden Cost of the Defaults

Every Linux engineer I know who runs Debian has, at some point,
installed it through the default graphical installer. The
experience is competent. The questions are minimal. The result is
a working Debian system in about twenty minutes. For most use cases
this is the right product, and the Debian Installer team has spent
two decades refining it.

What the default installer does not advertise is the dozen choices
it makes silently. The mirror it selects. The packages it pulls in
from the "standard system utilities" task. The popularity-contest
opt-in default. The swap partition size formula. The APT
configuration. The locale generation. The GRUB defaults. Each
choice is reasonable on its own. The aggregate is a system that
contains a substantial amount of software you did not ask for,
configured in ways you did not specify, and that you will spend
months removing or reconfiguring if your use case differs from the
median Debian user.

The Expert Install in Advanced Options on the installer's main
menu unlocks every one of these choices explicitly. The
questions multiply from approximately fifteen to approximately
sixty. The total install time goes from twenty minutes to
forty-five. The result is a system that contains exactly what you
chose for it to contain, configured the way you specified.

This post is the case for paying the extra twenty-five minutes,
every time, on any Debian install you intend to operate beyond
the first reboot.

What the Default Installer Decides for You

The defaults are not arbitrary. They are reasonable choices for
the population of users who do not have specific opinions. The
problem is that if you are reading a blog called blog.c0xl.ch in
the first place, you almost certainly do have specific opinions.
The defaults are wrong for you.

The mirror selection uses a geographic heuristic. The result
is usually a national mirror that is competent but not optimal.
The actual fastest mirror for my Nottwil location is often a
specific Swiss university mirror that the default heuristic does
not surface. The expert installer lets me type the URL.

The standard system utilities task pulls in approximately one
hundred and seventy packages, including things like
bash-completion, bsdmainutils, cron, iptables, less,
logrotate, man-db, nano, openssh-client, procps, sudo,
vim-tiny, and a long list of others. Some of these I want. Some
of these (nano, vim-tiny) I will replace immediately with a
full vim. Some (bsdmainutils) I never use. The expert install
lets me opt out of this task entirely and add only what I
explicitly want.

The popularity-contest opt-in defaults to enabled on graphical
installs. The package reports anonymized usage statistics to the
Debian project, which is genuinely valuable to the project. It is
also a network call from every Debian machine I run, every week,
that I want to make consciously rather than by default.

The swap is configured as a partition equal in size to the
RAM. For systems with 32 GB of memory and SSDs, this is wasteful;
a zram-backed compressed swap of 8 GB is the better choice. For
systems with 4 GB of memory and a small disk, an 8 GB swap is
appropriate. The default formula does not know which case you are
in.

The APT configuration does not enable the security line by
default with contrib non-free non-free-firmware components.
Whether to add these is a deployment-specific choice. The expert
installer asks. The default installer does not.

The GRUB timeout defaults to five seconds. For a server, this
should be zero. For a dual-boot workstation, five is right. The
default does not differentiate.

The install user is added to the sudo group by default. For
a multi-user system or a system where the install user is not the
operational user, this is the wrong choice. The expert installer
asks. The default installer just does it.

None of these defaults is harmful. All of them are decisions you
might want to make differently. The Expert Install is the version
that asks.

What the Expert Install Adds

The screens that the Expert Install adds, in approximate order:

A choice between dialog and newt for the installer frontend
itself. Not consequential. The default is fine.

A choice of which installer modules to load. The default loads
what is needed. The expert mode lets you load network drivers,
filesystem modules, or hardware probes that the default heuristic
did not select. This matters for hardware that Debian does not
auto-detect cleanly, which in 2026 is almost nothing but
occasionally still a server with unusual storage controllers.

Manual language and locale configuration, including whether to
generate locales beyond the system default. Most systems do not
need en_US.UTF-8 and de_CH.UTF-8 and fr_CH.UTF-8 and so on.
Generating only the locales actually needed saves disk space and
makes locale -a legible.

Network configuration that exposes every option, including
explicit DHCP versus static, manual DNS server entry, the choice
of hostname versus FQDN, and the option to skip network
configuration entirely if you are installing without one.

Mirror selection with a free-form URL field. This is the screen
where you stop accepting the geographic heuristic and start using
the mirror you actually want. For Switzerland, that is typically
debian.ethz.ch (ETH Zurich) or one of the AS-level peering
mirrors that resolve faster than the regional default.

Partitioning with full manual control. The default installer
presents three or four partitioning recipes. The expert installer
adds the choice of filesystem (ext4, xfs, btrfs, jfs, reiserfs),
the choice of mount options (noatime, nodiratime, etc.), the
LVM configuration with explicit volume group and logical volume
sizing, the LUKS configuration with explicit cipher and key-size
choices, and the explicit /boot, /boot/efi, root, and swap
layout.

Package selection that lets you choose tasks individually and
add specific package names that the task selection would not have
included. The "standard system utilities" task can be unchecked
entirely if you want a base system with only what you specify.

GRUB configuration that asks where to install the bootloader,
whether to install on additional disks for redundancy, the
timeout, and whether to add custom kernel command-line parameters
at install time.

The final system tasks: hostname, root password policy
(including the option to disable root and rely on sudo), the
install user creation with explicit UID/GID/groups, and the
timezone with full IANA database access rather than the
geographic suggestion.

Approximately sixty questions, none of them difficult, all of them
about explicit choice.

The Result

The system you get after an Expert Install is a system you can
describe to another engineer in a sentence. "Debian 13 minimal,
no standard-system-utilities task, btrfs root with explicit
subvolumes, LUKS-encrypted, swap on zram, ETH Zurich mirror,
non-free-firmware enabled, no GRUB timeout, install user not in
sudo." Every line is something the installer asked about and you
chose.

The system you get after a default install is a system you have
to inspect to understand. What mirror did it pick? What packages
came in with the standard task? Is popularity-contest enabled? Is
swap as a partition or a file? You can answer all of these
questions by reading the installed system, but you should not
have to.

The difference matters most when you are running more than one
Debian system. The Expert Install is reproducible because every
choice was explicit. The default install is reproducible only to
the extent that the defaults happen to be stable across releases,
which they mostly are but not always. For a homelab with twenty
Debian-derived endpoints, the difference between "twenty systems
that contain exactly what I specified" and "twenty systems that
contain whatever Debian 13.1's default installer thought was
appropriate in May 2026" is a real operational quality.

The Honest Limits

The Expert Install takes longer. Twenty-five additional minutes per
install is real time. For a fleet rebuild, this adds hours. The
right response is to use preseed configuration for fleet
deployments, which captures every Expert Install choice in a text
file that the installer reads at boot. The preseed file is the
artifact that turns "this engineer's specific install choices"
into "this organization's standard build." Writing the first
preseed takes a few hours. Every subsequent install is faster
than the default would have been.

The questions are sometimes opaque. The expert installer assumes
you know what aptitude versus apt priority means, what
async mount options imply, what the difference between
grub-pc and grub-efi-amd64 is. The defaults are reasonable
for any of these if you do not have an opinion. The point is that
you see the question rather than having it answered for you.

Some Expert-Install screens have changed across Debian releases.
Debian 12 introduced the explicit non-free-firmware component
selection. Debian 13 added the option for systemd-boot as a
GRUB alternative on UEFI systems. The screens you remember from
Debian 11 are not exactly the screens of Debian 13. The
underlying philosophy is consistent. The specific questions
evolve with each release.

Closing

The defaults are not the enemy. The defaults are right for most
users. The Expert Install is not for elite users who somehow
deserve more control. It is for any user who wants to know what
their system actually contains, configured how, with what
packages, on what filesystem, using what mirror, with what
hardening choices applied.

Twenty-five minutes per install is the cost. The benefit is a
system that you can describe completely without inspecting it,
that you can reproduce by re-running the same choices, and that
contains exactly what you intended it to contain.

For one-off installs, this is a marginal improvement. For the
homelab, for the fleet of servers, for the laptops you actually
use day to day, the Expert Install is the discipline that
distinguishes systems you are operating from systems that happen
to be running on your hardware.

Advanced Options → Expert Install on every Debian Installer
boot menu. Twenty-five extra minutes. The system that comes out
the other end is the system you actually wanted.