Working with Hardware

In this lesson, we explore how Linux detects and manages hardware devices connected to a system. You will learn about various command-line tools that list devices and provide detailed hardware information using the example of a USB disk. When a USB disk is attached, the corresponding device driver in the Linux kernel identifies the state change and generates a uEvent. This event is forwarded to the user-space device manager daemon, uDev, which then dynamically creates a device node under the /dev filesystem for the new drive.

Once this process completes, the new disk appears in the /dev filesystem.

Viewing Kernel and Device Events

The dmesg tool displays messages from the kernel's ring buffer, including extensive boot-time logs that reveal how hardware was detected and configured. You can pipe the output to utilities like less or filter it with grep to search for specific keywords.

The udevadm utility is used to query and monitor device events related to uDev. For example, the following command queries the uDev database and returns the device path associated with a hard disk:

[~]$ udevadm info --query=path --name=/dev/sda5
/devices/pci0000:00/0000:00:17.0/ata3/host2/target2:0:0/2:0:0:0/block/sda/sda5

Additionally, you can monitor kernel uEvents in real time with:

[~]$ udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

Listing PCI Devices

The lspci command lists all PCI devices configured in your system, such as Ethernet cards, RAID controllers, video cards, and wireless adapters. PCI stands for Peripheral Component Interconnect, representing devices directly attached to the motherboard.

Below is an example output from the lspci command:

[~]$ lspci
00:00.0 Host bridge: Intel Corporation Device 3e34 (rev 0c)
00:02.0 VGA compatible controller: Intel Corporation Device 3ea0 (rev 02)
00:08.0 System peripheral: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th Gen Core Processor Gaussian Mixture Model
00:12.0 Signal processing controller: Intel Corporation Device 9df9 (rev 30)
00:14.0 USB controller: Intel Corporation Device 9ded (rev 30)
00:14.2 RAM memory: Intel Corporation Device 9def (rev 30)
00:14.3 Network controller: Intel Corporation Device 9df0 (rev 30)
00:15.0 Serial bus controller [0c80]: Intel Corporation Device 9de8 (rev 30)
00:15.1 Serial bus controller [0c80]: Intel Corporation Device 9de9 (rev 30)
00:16.0 Communication controller: Intel Corporation Device 9de0 (rev 30)
00:17.0 RAID bus controller: Intel Corporation 82801 Mobile SATA Controller [RAID mode] (rev 30)
00:1c.0 PCI bridge: Intel Corporation Device 9db0 (rev f0)
00:1f.0 ISA bridge: Intel Corporation Device 9dab (rev 30)
00:1f.3 Audio device: Intel Corporation Device 9dc8 (rev 30)
00:1f.5 Serial bus controller [0c80]: Intel Corporation Device 9dad (rev 30)
01:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTL8411B PCI Express Card Reader (rev 01)
01:00.1 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 12)

Viewing Block Devices

The lsblk command provides detailed information about block devices present on your system. It displays the physical disk (e.g., sda) along with its partitions (e.g., sda1 to sda5). The term "disk" refers to the entire physical disk, while each "partition" is a section of that disk. Devices are also linked with major and minor numbers—where the major number signifies the device driver type (for example, the number 8 indicates a block disk device) and the minor number distinguishes between individual devices handled by the same driver.

Example output from the lsblk command:

[~]$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda    8:0    0 119.2G 0 disk 
├─sda1 8:1    0   100M 0 part /boot/efi
├─sda2 8:2    0    16M 0 part 
├─sda3 8:3    0  71.5G 0 part 
├─sda4 8:4    0    1G 0 part 
└─sda5 8:5    0  46.6G 0 part /

Another example showing the associated major numbers:

[~]$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda           8:0    0 119.2G  0 disk
├─sda1        8:1    0   100M  0 part /boot/efi
├─sda2        8:2    0    16M  0 part
├─sda3        8:3    0  71.5G  0 part
├─sda4        8:4    0     1G  0 part
└─sda5        8:5    0  46.6G  0 part /

Displaying CPU Information

The lscpu command offers detailed insights into the CPU architecture, such as the number of cores, threads per core, cache sizes, and more.

For instance, the output below illustrates a 64-bit processor with one physical CPU socket, four cores per socket, and two threads per core—resulting in a total of 8 virtual CPUs:

[~]$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 142
Model name:            Intel(R) Core(TM) i5-8265U CPU @ 1.60GHz
Stepping:              12
CPU MHz:               700.060
CPU max MHz:           3900.0000
CPU min MHz:           400.0000
BogoMIPS:              3600.00
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              6144K
NUMA node0 CPU(s):     0-7

Key points from the output include:

• The CPU architecture is 64-bit.
• There is 1 socket with 4 cores each and 2 threads per core, totaling 8 virtual CPUs.

Displaying Memory Information

To retrieve memory configuration details, use the lsmem command. When combined with the --summary flag, it delivers a brief overview of the system's memory:

[~]$ lsmem --summary
Memory block size: 128M
Total online memory: 8G
Total offline memory: 0B

For a more detailed view, run lsmem without any flags.

Alternatively, the free command shows memory usage statistics, including total, used, and free memory. The -m flag displays the information in megabytes:

[~]$ free -m
              total        used        free      shared  buff/cache   available
Mem:          7824       2518         541        525        4764       4481
Swap:         2047          0       2047

You can also use -k for kilobytes and -g for gigabytes as needed.

Extracting Detailed Hardware Information

The lshw command extracts comprehensive details about the system's hardware configuration. This includes memory setup, firmware version, motherboard information, CPU, cache settings, and bus speeds. Note that running lshw without root privileges may generate warnings about incomplete or inaccurate output.

For example, if Bob runs lshw without root, he might see a warning. Dave explains that certain commands require root privileges for complete output. To run lshw with elevated privileges, use sudo:

[~]$ sudo lshw
[sudo] password for bob:
  description: Notebook
  product: Aspire A515-52 (0000000000000000)
  vendor: Acer
  version: V1.12
  serial: NXH89AA0026262680A13400
  width: 64 bits
  capabilities: smbios-3.0 dmi-3.0 smp vsyscall32
  configuration: chassis=notebook family=Aspire 5 sku=0000000000000000 uuid=D74676912-9EFF-ABCD-8192-085643E554D
*-core
     description: Motherboard
     product: Raticate_WL
     vendor: WL
     physical id: 0
     version: V1.12
     serial: LAC2110069561AB521500
     slot: Type2 - Board Chassis Location
*-firmware
     description: BIOS
     vendor: Insyde Corp.
     physical id: 0
     version: V1.12
     date: 04/26/2019
     size: 128KiB
     capacity: 15MiB

Dave further explains that each user must enter their own password when using sudo. After proper authentication, the command output is displayed without warnings. The sudo mechanism logs all superuser command activity for auditing purposes. Below is another example of the sudo lshw output:

[~]$ sudo lshw
[sudo] password for bob:
description: Notebook
   product: Aspire A515-52 (000000000000000000000000)
   vendor: Acer
   version: V1.12
   serial: NXH89AA0026262680A13400
   width: 64 bits
   capabilities: smbios-3.0 dmi-3.0 smp vsyscall32
   configuration: chassis=notebook family=Aspire 5 sku=00000000000000000000 uuid=D74676912-9EFF-ABCD-8192-085643E554D
*-core
   description: Motherboard
   product: Raticate_WL
   vendor: WL
   physical id: 0
   version: V1.12
   serial: LAC12110069651AB521500
   slot: Type2 - Board Chassis Location
*-firmware
   description: BIOS
   vendor: Insyde Corp.
   physical id: 0
   version: V1.12
   date: 04/26/2019
   size: 128KiB
   capacity: 15MiB

Summary

Linux offers a wide range of tools to monitor and manage hardware devices, system configuration, and resource usage. Understanding these commands and interpreting their outputs is crucial for effective system administration and troubleshooting. Regularly using these tools enhances your ability to manage Linux environments efficiently and securely.

Happy learning!