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---
title: "The Case of the Bloated Boot"
date: 2025-09-22
lastmod: 2025-09-22
categories: ["Blog"]
tags: ["linux"]
---
When `sudo mkinitcpio -P` fails because your boot partition is full, you've got
a fun problem. The culprit? That massive fallback initramfs taking up precious
space on a tiny boot partition.
<!--more-->
# The Problem
Picture this: you're dual-booting Linux and running a system update when
suddenly `mkinitcpio` fails to generate the larger fallback image. Your boot
partition is completely stuffed.
```bash
$ df -h /boot
Filesystem Size Used Avail Use% Mounted on
/dev/nvme0n1p1 256M 256M 0 100% /boot
```
**Yikes.** Time to investigate what's eating all that space.
# Damage Assessment
A quick `du -sh` reveals the usual suspects:
```bash
$ du -sh /boot/*
157M /boot/initramfs-linux-fallback.img
52M /boot/initramfs-linux.img
16M /boot/vmlinuz-linux
30M /boot/EFI
```
The fallback initramfs is **three times larger** than the normal one. But why?
# The Autodetect Mystery
The secret lies in one simple flag in `/etc/mkinitcpio.d/linux.preset`:
```bash
fallback_options="-S autodetect"
```
That `-S autodetect` flag skips the autodetect hook, which normally shrinks your
initramfs by only including modules your hardware actually needs. Without it,
mkinitcpio includes **everything**.
## By the Numbers
Here's what that means in practice for me:
| Component | Normal (with autodetect) | Fallback (no autodetect) | Ratio |
| :----------------- | -----------------------: | -----------------------: | ------: |
| **Kernel modules** | 190 modules | 6,319 modules | **33x** |
| **Firmware files** | 711 files | 2,996 files | **4x** |
| **Total size** | 52M | 157M | **3x** |
The fallback image is essentially a universal boot disk that works on _any_
hardware — your laptop, your friend's desktop, that ancient server in the
closet. It includes drivers for RAID controllers you don't have, network cards
from 2003, and GPU firmware for every generation of graphics hardware.
# The Nuclear Option
Since I never use the fallback image anyway (live USB for rescue), the
solution was just to get rid of this:
1. **Remove the fallback image** to free immediate space:
```bash
sudo rm /boot/initramfs-linux-fallback.img
```
2. **Disable future generation** by editing `/etc/mkinitcpio.d/linux.preset`:
```bash
# Change this line:
PRESETS=('default' 'fallback')
# To this:
PRESETS=('default')
```
3. **Test it works**:
```bash
sudo mkinitcpio -P
```
Result: boot partition goes from 100% to 39% usage, and future kernel updates
won't recreate the bloated fallback.
# Why It Matters
The autodetect hook is actually quite clever. On my system with 443MB of total
kernel modules available, it correctly identified that I only need 190 of them
— things like my specific WiFi driver, filesystem modules for ext4 and LVM, and
encryption support for LUKS.
The fallback includes _everything else too_: drivers for hardware I'll never own
(_especially since this is on a laptop_), filesystem support for formats I'll
never use, and network protocols from the dawn of time. It's the digital
equivalent of packing for a trip by bringing your entire garage of tools "just
in case"
# The Takeaway
Unless you're regularly swapping hardware or need guaranteed boot recovery from
the initramfs itself, the fallback image is dead weight. Modern autodetection
works well enough that most people never need it. I've personnally never, ever
used the fallback image and for the context of this laptop probably never will
as a bootable USB is my go-to for any and all boot issues.
For those tight boot partitions in dual-boot setups, disabling fallback
generation is it. Save the space for kernel updates that actually matter :^)
And if you _do_ need recovery? Well, that's what live USBs are for, but you're
welcome to make your own decisions.

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---
title: "Fingerprint Support on Lenovo Yoga 6 with Arch Linux"
date: 2025-09-23
lastmod: 2025-09-23
categories: ["Blog"]
tags: ["linux", "archlinux", "hardware"]
---
Got a Lenovo Yoga 6 2-in-1 and frustrated that your fingerprint reader isn't working on Arch Linux? You're not alone. The standard fprintd package doesn't include the necessary firmware for this laptop's Synaptics sensor.
<!--more-->
# The Problem
The Lenovo Yoga 6 2-in-1 laptop comes with a Synaptics fingerprint sensor that requires proprietary firmware not included in the standard fprintd package. Without this firmware, fprintd can't communicate with the sensor, leaving you with a non-functional fingerprint reader.
# The Solution
The AUR package `libfprint-2-tod1-synatudor-git` provides the necessary Touch-On-Display (TOD) driver and firmware for Synaptics sensors, including the one in the Yoga 6.
## Installation Steps
1. **Install the AUR package:**
```bash
yay -S libfprint-2-tod1-synatudor-git
```
Or if you're using paru:
```bash
paru -S libfprint-2-tod1-synatudor-git
```
2. **Install fprintd (if not already installed):**
```bash
sudo pacman -S fprintd
```
3. **Enable and start the fprintd service:**
```bash
sudo systemctl enable --now fprintd.service
```
4. **Verify the fingerprint reader is detected:**
```bash
fprintd-list-devices
```
You should see output listing your Synaptics sensor.
## Setting Up Fingerprints
Once the driver is installed and working:
1. **Enroll your fingerprints:**
```bash
fprintd-enroll
```
Follow the prompts to scan your finger multiple times.
2. **Test authentication:**
```bash
fprintd-verify
```
## PAM Integration
To use fingerprint authentication for system login and authentication, add fingerprint support to the appropriate PAM configuration files:
1. **For system login**, add to `/etc/pam.d/system-local-login`:
```
auth sufficient pam_fprintd.so
```
2. **For display managers**, the configuration may already exist:
- SDDM: `/etc/pam.d/sddm` should have `auth sufficient pam_fprintd.so`
- LightDM: `/etc/pam.d/lightdm` should have `auth sufficient pam_fprintd.so`
3. **For sudo authentication**, add to `/etc/pam.d/sudo`:
```
auth sufficient pam_fprintd.so
```
The `sufficient` directive means fingerprint authentication will be attempted first, falling back to password if fingerprint fails.
# Why This Works
The `libfprint-2-tod1-synatudor-git` package provides:
- The proprietary Synaptics firmware blob required by the sensor
- The TOD (Touch-On-Display) driver implementation for libfprint2
- Proper USB device ID mappings for various Synaptics sensors
Without this package, fprintd only has access to open-source drivers that don't support the proprietary communication protocol used by many modern fingerprint sensors.
# Troubleshooting
If the fingerprint reader still doesn't work:
1. **Check USB device detection:**
```bash
lsusb | grep -i synaptics
```
2. **Review fprintd logs:**
```bash
journalctl -u fprintd -b
```
3. **Ensure secure boot is disabled** - some proprietary firmware doesn't load with secure boot enabled.
4. **Reboot after installation** - the driver may need a fresh start to properly initialize.
# Final Notes
While it's unfortunate that proprietary firmware is required, this AUR package makes fingerprint authentication possible on the Yoga 6 and similar laptops with Synaptics sensors. The convenience of fingerprint login, especially on a 2-in-1 device, is worth the extra installation step.