LPIC-1 101.1 — Determine and Configure Hardware Settings

Exam weight: 2 — LPIC-1 v5, Exam 101

What you need to know

• Enable and disable integrated peripheral devices
• Distinguish between types of mass storage devices
• Determine hardware resources for devices
• Work with hardware inspection tools: lsusb, lspci
• Manage USB devices
• Understand the concepts of sysfs, udev and dbus

BIOS and UEFI: configuration before the OS loads

Before the operating system starts, hardware can be configured directly in the BIOS or UEFI utility. You enter it at power-on by pressing the appropriate key — usually Del, F2 or F12. The exact key depends on the manufacturer and is typically shown on screen during POST.

BIOS (Basic Input/Output System) was used on x86 motherboards until the mid-2000s. From the late 2000s onwards it began to be replaced by UEFI (Unified Extensible Firmware Interface), which offers richer capabilities: device identification, testing, configuration and firmware updates. In practice both are still commonly called “BIOS” because they serve the same purpose.

What you can do in BIOS/UEFI:

• Enable or disable integrated peripherals (NIC, Bluetooth, serial ports)
• Change IRQ and DMA assignments for devices
• Set boot order so the system boots from the right disk
• Enable or disable CPU features (disabling saves power and closes certain vulnerabilities)
• Set correct RAM timings and frequency per manufacturer spec

If the OS fails to boot without an obvious reason, the first thing to check is the boot device order in BIOS/UEFI.

Filesystems and pseudo-filesystems

Linux provides three pseudo-filesystems through which you can read hardware information in real time.

/proc/

/proc/ stores no real files on disk. It is a virtual filesystem the kernel generates on the fly. It holds information about running processes and system state.

Useful files:

/proc/cpuinfo       — CPU information
/proc/meminfo       — memory information
/proc/interrupts    — interrupt table (IRQ)
/proc/ioports       — I/O port ranges
/proc/dma           — DMA channels in use
/proc/bus/pci/      — PCI devices

Example — view the CPU model:

cat /proc/cpuinfo | grep "model name"

/sys/

/sys/ appeared after /proc/ and is called sysfs. Here the kernel exports the device and driver hierarchy as a directory tree. Every device in the system gets its own directory.

For example, find network card information here:

ls /sys/class/net/

Read a specific device parameter, such as link state:

cat /sys/class/net/eth0/operstate

/dev/

/dev/ contains device files. When you open /dev/sda you are communicating with the first hard disk. When you write to /dev/null, data simply disappears.

Device file types:

• Block (b): hard disks, SSDs, USB drives (/dev/sda, /dev/nvme0n1)
• Character (c): terminals, serial ports (/dev/tty0, /dev/ttyS0)

List all block devices:

ls -l /dev/sd*

sysfs, udev and dbus

sysfs

sysfs, mounted at /sys/, exports kernel, device and driver information. It is the primary interface between userspace and the kernel’s device subsystem.

udev

udev manages dynamic device files in /dev/. The kernel detects a device event and passes it to the udev process, which creates the corresponding files in /dev/ according to predefined rules.

udev handles two scenarios:

• Coldplug — devices already connected when the machine powers on. udev processes them during system startup.
• Hotplug — devices connected while the system is running (e.g. a USB flash drive). The kernel supports hotplug since version 2.6.

udev relies on sysfs (/sys/) for device information. Rules for device identification are stored in /etc/udev/rules.d/. Base rules are provided by the distribution; you can add your own for specific cases.

Monitor device events in real time:

udevadm monitor

dbus

D-Bus is a message bus through which processes communicate with each other. For example, Network Manager uses D-Bus to notify the desktop about a network change. Systemd relies heavily on D-Bus for service management.

Types of mass storage devices

All storage devices in Linux are called block devices because data is read and written in buffered blocks.

Starting with kernel 2.4, most storage devices are represented as SCSI devices regardless of the actual connection type. IDE, SATA, SSD and USB drives all receive the sd prefix.

Legacy IDE naming: first IDE channel master /dev/sda, slave /dev/sdb; second channel master /dev/sdc, slave /dev/sdd. An optical drive on the second channel gets /dev/hdc in the old notation.

Partition naming: for sd disks just append a number: /dev/sda1, /dev/sda2. For NVMe and MMC a p is inserted between the disk name and partition number: /dev/nvme0n1p1, /dev/mmcblk0p1.

Hardware resources

Each device uses one or more resources:

IRQ (Interrupt Request) — interrupt line the device uses to signal the CPU. View current assignments:

cat /proc/interrupts

I/O Ports — address ranges for data exchange with the device:

cat /proc/ioports

DMA (Direct Memory Access) — channels for direct memory access, bypassing the CPU:

cat /proc/dma

Memory-mapped I/O — physical memory ranges reserved for devices.

Working with kernel modules

Device drivers in Linux are loaded as kernel modules. Here are the main tools.

lsmod

Lists all loaded modules:

lsmod

Output has three columns:

The Used by column matters for troubleshooting: you cannot unload a module that other modules depend on. For example, snd_hda_intel pulls in snd_hda_codec, snd_pcm and other audio modules.

Filter output by name:

lsmod | grep snd_hda_intel

modprobe

Loads or unloads a module along with all its dependencies:

# Load a module
sudo modprobe bluetooth

# Unload a module and all dependents (if not in use)
sudo modprobe -r snd-hda-intel

Unlike insmod, modprobe resolves dependencies automatically. The -r flag unloads the module only if no running process is using it.

Module parameters can be passed directly at load time:

sudo modprobe nouveau modeset=0

To apply parameters on every boot, add them to a file in /etc/modprobe.d/:

# /etc/modprobe.d/nouveau.conf
options nouveau modeset=0

modinfo

Shows the module description, file path, author, license, dependencies and available parameters:

modinfo bluetooth

The -p flag lists only the available parameters, nothing else:

modinfo -p nouveau

Example output:

modeset:enable driver (default: auto, 0 = disabled, 1 = enabled) (int)
noaccel:disable kernel/abi16 acceleration (int)

This is useful before writing parameters to /etc/modprobe.d/.

Inspecting PCI devices: lspci

lspci lists all devices connected to the PCI/PCIe bus — video cards, NICs, SATA controllers, USB expansion cards. Some devices are soldered onto the motherboard; others are inserted into expansion slots.

Note: many hardware commands require root privileges or show limited output for regular users. Use sudo.

Basic output:

lspci

Example:

01:00.0 VGA compatible controller: NVIDIA Corporation GM107 [GeForce GTX 750 Ti]
04:02.0 Network controller: Ralink corp. RT2561/RT61 802.11g PCI

The hex numbers at the start of each line (e.g. 04:02.0) are the unique PCI bus address of the device.

Detailed information for a specific device by its address:

lspci -s 04:02.0 -v

Output shows flags, IRQ, memory range and a kernel driver in use line with the loaded module name.

Other useful flags:

lspci -s 01:00.0 -k   # module in use + all available modules
lspci -v               # verbose output for all devices
lspci -vv              # very verbose
lspci -nn              # add numeric vendor and device IDs

Example output of lspci -s 01:00.0 -k:

01:00.0 VGA compatible controller: NVIDIA Corporation GM107 [GeForce GTX 750 Ti]
    Kernel driver in use: nvidia
    Kernel modules: nouveau, nvidia_drm, nvidia

Kernel driver in use is the active driver; Kernel modules lists all available modules for this device.

Three signs a device is working correctly:

1. The device is detected (lspci sees it)
2. A suitable kernel module is loaded (Kernel driver in use is present)
3. The device is ready to use

Inspecting USB devices: lsusb

lsusb lists all USB devices in the system, including hubs. Keyboards, mice and removable storage most commonly use the USB interface.

Basic output:

lsusb

Example:

Bus 001 Device 028: ID 093a:2521 Pixart Imaging, Inc. Optical Mouse
Bus 001 Device 020: ID 1131:1001 Integrated System Solution Corp. KY-BT100 Bluetooth Adapter
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Line format: bus (Bus 001), device number (Device 028), ID as vendorid:productid, description.

Select a device by bus and device number (from lsusb -t output):

lsusb -s 01:20

Detailed information for a specific device by its ID:

lsusb -v -d 1781:0c9f

This shows the full device descriptor: class, protocol, packet size, USB version and more. If a device appears in lsusb -t but the Driver= field is empty, either the module is not loaded or the device is managed directly by an application without a kernel module.

Show device tree with ports and drivers:

lsusb -t

Example output of lsusb -t:

/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 3: Dev 20, If 0, Class=Wireless, Driver=btusb, 12M
    |__ Port 1: Dev 7, If 0, Class=Vendor Specific Class, Driver=lan78xx, 480M

The tree shows which port each device is connected to, its class and active driver.

Managing USB devices

Beyond lsusb, there are several ways to interact with USB devices.

Monitor connection events via udev:

udevadm monitor --subsystem-match=usb

Get detailed device information via udev:

udevadm info -a -n /dev/sdb

Set a udev rule for a specific USB device (file /etc/udev/rules.d/99-my-usb.rules):

SUBSYSTEM=="usb", ATTR{idVendor}=="046d", ATTR{idProduct}=="c52b", MODE="0666"

Enabling and disabling peripherals

Integrated peripherals (Wi-Fi, Bluetooth, serial ports) are often configured in BIOS/UEFI. From Linux you can control them via:

1. Unloading the kernel module: sudo modprobe -r iwlwifi disables Wi-Fi
2. Blocklist in /etc/modprobe.d/: prevents the module from loading at boot

Two approaches for blacklisting. You can add a line to the existing /etc/modprobe.d/blacklist.conf:

blacklist nouveau

The preferred approach is to create a separate file for just the module:

# /etc/modprobe.d/nouveau.conf
blacklist nouveau

This is needed, for example, when the proprietary nvidia driver is installed and the default nouveau module needs to be kept out of the way.

After making changes, rebuild initramfs:

sudo update-initramfs -u

Exam command reference

# PCI device information
lspci
lspci -k        # with module names
lspci -nn       # with numeric IDs

# USB device information
lsusb
lsusb -t        # as a tree
lsusb -v        # verbose

# Kernel modules
lsmod           # list loaded modules
modprobe name   # load a module
modprobe -r name  # unload a module
modinfo name    # module information

# Hardware resources
cat /proc/interrupts
cat /proc/ioports
cat /proc/dma

# udev
udevadm monitor
udevadm info -a -n /dev/device

Typical exam questions

1. What is the successor to BIOS on x86 systems? → UEFI
2. Which file shows IRQ assignments? → /proc/interrupts
3. Which command loads a module with dependencies? → modprobe
4. What is udev? → Dynamic device file manager
5. Where are device files stored? → /dev/
6. How does /sys/ differ from /proc/? → /sys/ is specialized for device structure; /proc/ covers processes and general kernel state
7. Which command shows the driver for a PCI device? → lspci -k
8. How do you view kernel module parameters? → modinfo -p module_name
9. Where are persistent module parameters stored? → /etc/modprobe.d/
10. What is coldplug? → Detection of devices already connected when the system starts
11. How are NVMe partitions named? → /dev/nvme0n1p1, /dev/nvme0n1p2
12. How are SD card partitions named? → /dev/mmcblk0p1, /dev/mmcblk0p2
13. What is the preferred way to blacklist a module? → Create a dedicated file /etc/modprobe.d/module_name.conf with a blacklist directive

Related topics

• 101.2 Boot the System — system boot process
• 101.3 Change runlevels / boot targets — runlevels
• 102.1 Design hard disk layout — disk partitioning

Exercises

Exercise 1 — SATA disk boot order

A system stops booting after a second SATA disk is added. All components are working. What is the likely cause?

Exercise 2 — Inspecting a video card with lspci

You need to check the specs of a discrete video card connected to the PCI bus without opening the case. Which command do you use?

lspci -v

lspci -s 01:00.0 -v

Exercise 3 — Kernel module for a RAID controller

The lspci output contains this line:

03:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 2208 [Thunderbolt] (rev 05)

Which command shows the loaded kernel module for this device?

lspci -s 03:00.0 -k

Exercise 4 — Module unload failure

An administrator tries to unload the bluetooth module with modprobe -r bluetooth and gets:

modprobe: FATAL: Module bluetooth is in use.

What is the cause?

Exercise 5 — Headless boot on legacy BIOS

On older servers with a legacy BIOS, the system refuses to boot if no keyboard is connected. How do you fix this?

Exercise 6 — No lspci on ARM

On single-board computers like the Raspberry Pi (ARM), the lspci command is not present. Why?

Exercise 7 — USB drive on a Linux router

An external USB hard drive is connected to a Linux-based router. There are no other block devices. What will it be called in /dev/?

/dev/sda

Exercise 8 — Checking for the Meltdown vulnerability

How do you check whether the current system is affected by Meltdown?

grep bugs /proc/cpuinfo

cat /sys/devices/system/cpu/vulnerabilities/meltdown

LPIC-1 Study Notes | Topic 101: System Architecture