This is a riveting series:

On the LPIC-1 Exam 101: System Architecture
On the LPIC-1 Exam 101: Linux Installation and Package Management
On the LPIC-1 Exam 101: GNU and Unix Commands
On the LPIC-1 Exam 101: Devices, Linux Filesystems, FHS

When studying for the Linux Professional Institute LPIC-1 certification, I took a bunch of notes when reading the docs and doing an online course. Note that this is not exhaustive, so do not depend on this article to get you prepared for the exam.

The menu items below are not in any order.

This roughly covers Topic 101: System Architecture.

Caveat emptor.

Exam Details
Topic 101: System Architecture
Summary
References

Exam Details

LPIC-1 Exam 101

Exam Objectives Version: 5.0
Exam Code: 101-500

Topic 101: System Architecture

Block Devices and Hardware Settings

These commands can be valuable for getting hardware attributes for a given device that can be used when creating udev rules.

`blkid`

Prints block device attributes:

$ sudo blkid
/dev/nvme0n1p1: UUID="892E-F9C9" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="9cb384f4-1405-4a5d-8fa7-7127549889cb"
/dev/nvme0n1p2: UUID="400bebc0-1270-4c2c-9c0b-255d3e1143e4" BLOCK_SIZE="1024" TYPE="ext2" PARTUUID="a6aa0d1c-b8f9-49c4-a111-317542c3df03"
/dev/nvme0n1p3: UUID="c1334d3a-d586-49ee-b8a9-37a2a36da46c" TYPE="crypto_LUKS" PARTUUID="b0245516-cf6d-4a86-a154-79661b67bb05"
/dev/mapper/nvme0n1p3_crypt: UUID="DIjCje-JxlM-HL0D-9BqL-puZl-x34V-dDFL8U" TYPE="LVM2_member"
/dev/mapper/kilgore--trout--vg-root: UUID="6d4a9ce3-9412-4261-b873-974c29447e79" BLOCK_SIZE="4096" TYPE="ext4"
/dev/mapper/kilgore--trout--vg-swap_1: UUID="3d46ebcb-fd6c-4a94-8f1d-1a945cb4b7ae" TYPE="swap"

Note that it displays the filesystem of a block device as an attribute.

`lsblk`

The lsblk system administrator command will list all available block devices, including swap space, but not RAM disks. It gets its information from sysfs and the udev db.

The man page notes that it’s safest to call udevadm settle before any lsblk commands, which watches the udev event queue, and exits if all current events are handled.

Print dependencies in reverse order:

$ sudo lsblk -s
NAME                      MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
kilgore--trout--vg-root   253:1    0 474.9G  0 lvm   /
└─nvme0n1p3_crypt         253:0    0 475.9G  0 crypt
  └─nvme0n1p3             259:3    0   476G  0 part
    └─nvme0n1             259:0    0 476.9G  0 disk
kilgore--trout--vg-swap_1 253:2    0   976M  0 lvm   [SWAP]
└─nvme0n1p3_crypt         253:0    0 475.9G  0 crypt
  └─nvme0n1p3             259:3    0   476G  0 part
    └─nvme0n1             259:0    0 476.9G  0 disk
nvme0n1p1                 259:1    0   512M  0 part  /boot/efi
└─nvme0n1                 259:0    0 476.9G  0 disk
nvme0n1p2                 259:2    0   488M  0 part  /boot
└─nvme0n1                 259:0    0 476.9G  0 disk

A nvme device is an SSD connected to the PCI Express bus.

Many commands allow you to specify columns, and lsblk is no different:

$ sudo lsblk -o NAME,SIZE
NAME                              SIZE
nvme0n1                         476.9G
├─nvme0n1p1                       512M
├─nvme0n1p2                       488M
└─nvme0n1p3                       476G
  └─nvme0n1p3_crypt             475.9G
    ├─kilgore--trout--vg-root   474.9G
    └─kilgore--trout--vg-swap_1   976M

Print information about filesystems:

$ lsblk -f
NAME                            FSTYPE      FSVER    LABEL UUID                                   FSAVAIL FSUSE% MOUNTPOINT
nvme0n1
├─nvme0n1p1                     vfat        FAT32          892E-F9C9                                 500M     2% /boot/efi
├─nvme0n1p2                     ext2        1.0            400bebc0-1270-4c2c-9c0b-255d3e1143e4    346.8M    21% /boot
└─nvme0n1p3                     crypto_LUKS 2              c1334d3a-d586-49ee-b8a9-37a2a36da46c
  └─nvme0n1p3_crypt             LVM2_member LVM2 001       DIjCje-JxlM-HL0D-9BqL-puZl-x34V-dDFL8U
    ├─kilgore--trout--vg-root   ext4        1.0            6d4a9ce3-9412-4261-b873-974c29447e79    413.8G     6% /
    └─kilgore--trout--vg-swap_1 swap        1              3d46ebcb-fd6c-4a94-8f1d-1a945cb4b7ae                  [SWAP]
kilgore-trout ~~> ~/projects/benjamintoll.com:master

Note that this option is the same as -o NAME,FSTYPE,LABEL,UUID,FSAVAIL,FSUSE%,MOUNTPOINT.

The man page notes that the authoritative information about filesystems and raids is provided by the blkid command.

Print all available blocks, including RAM disks and empty devices:

$ sudo lsblk -a
NAME                            MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                               8:0    1     0B  0 disk
nvme0n1                         259:0    0 476.9G  0 disk
├─nvme0n1p1                     259:1    0   512M  0 part  /boot/efi
├─nvme0n1p2                     259:2    0   488M  0 part  /boot
└─nvme0n1p3                     259:3    0   476G  0 part
  └─nvme0n1p3_crypt             253:0    0 475.9G  0 crypt
    ├─kilgore--trout--vg-root   253:1    0 474.9G  0 lvm   /
    └─kilgore--trout--vg-swap_1 253:2    0   976M  0 lvm   [SWAP]

Output full device paths:

$ sudo lsblk -p
NAME                                        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
/dev/nvme0n1                                259:0    0 476.9G  0 disk
├─/dev/nvme0n1p1                            259:1    0   512M  0 part  /boot/efi
├─/dev/nvme0n1p2                            259:2    0   488M  0 part  /boot
└─/dev/nvme0n1p3                            259:3    0   476G  0 part
  └─/dev/mapper/nvme0n1p3_crypt             253:0    0 475.9G  0 crypt
    ├─/dev/mapper/kilgore--trout--vg-root   253:1    0 474.9G  0 lvm   /
    └─/dev/mapper/kilgore--trout--vg-swap_1 253:2    0   976M  0 lvm   [SWAP]

Print as JSON:

$ sudo lsblk -pJ
{
   "blockdevices": [
      {"name":"/dev/nvme0n1", "maj:min":"259:0", "rm":false, "size":"476.9G", "ro":false, "type":"disk", "mountpoint":null,
         "children": [
            {"name":"/dev/nvme0n1p1", "maj:min":"259:1", "rm":false, "size":"512M", "ro":false, "type":"part", "mountpoint":"/boot/efi"},
            {"name":"/dev/nvme0n1p2", "maj:min":"259:2", "rm":false, "size":"488M", "ro":false, "type":"part", "mountpoint":"/boot"},
            {"name":"/dev/nvme0n1p3", "maj:min":"259:3", "rm":false, "size":"476G", "ro":false, "type":"part", "mountpoint":null,
               "children": [
                  {"name":"/dev/mapper/nvme0n1p3_crypt", "maj:min":"253:0", "rm":false, "size":"475.9G", "ro":false, "type":"crypt", "mountpoint":null,
                     "children": [
                        {"name":"/dev/mapper/kilgore--trout--vg-root", "maj:min":"253:1", "rm":false, "size":"474.9G", "ro":false, "type":"lvm", "mountpoint":"/"},
                        {"name":"/dev/mapper/kilgore--trout--vg-swap_1", "maj:min":"253:2", "rm":false, "size":"976M", "ro":false, "type":"lvm", "mountpoint":"[SWAP]"}
                     ]
                  }
               ]
            }
         ]
      }
   ]
}

Remember that device mapper names are soft links:
$ readlink -f /dev/mapper/kilgore--trout--vg-root
/dev/dm-1

Weeeeeeeeeeeeeeeeeeeeeee

`lscpu`

This lscpu utility comes from the util-linux package:

$ dpkg -S $(which lscpu)
util-linux: /usr/bin/lscpu

This utility gets its information from /proc/cpuinfo.

$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
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) i7-8650U CPU @ 1.90GHz
Stepping:                        10
CPU MHz:                         802.816
CPU max MHz:                     4200.0000
CPU min MHz:                     400.0000
BogoMIPS:                        4199.88
Virtualization:                  VT-x
L1d cache:                       128 KiB
L1i cache:                       128 KiB
L2 cache:                        1 MiB
L3 cache:                        8 MiB
NUMA node0 CPU(s):               0-7
Vulnerability Itlb multihit:     KVM: Mitigation: Split huge pages
Vulnerability L1tf:              Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds:               Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:          Mitigation; PTI
Vulnerability Mmio stale data:   Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Retbleed:          Mitigation; IBRS
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:        Mitigation; IBRS, IBPB conditional, RSB filling, PBRSB-eIBRS Not affected
Vulnerability Srbds:             Mitigation; Microcode
Vulnerability Tsx async abort:   Mitigation; Clear CPU buffers; SMT vulnerable
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse s
                                 se2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtop
                                 ology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma c
                                 x16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_
                                 lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriori
                                 ty ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx rdseed adx smap clf
                                 lushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window h
                                 wp_epp md_clear flush_l1d arch_capabilities

`lsdev`

This lsdev utility comes from the procinfo package:

$ dpkg -S $(which lsdev)
procinfo: /usr/bin/lsdev

It pulls its information from the following locations:

/proc/dma
/proc/interrupts
/proc/ioports

So, it’s a quick overview of which hardware uses what I/O addresses and what IRQ and DMA channels:

$ sudo lsdev | head -20
Device            DMA   IRQ  I/O Ports
------------------------------------------------
 0  rmi4-00.fn34        162
 1  rmi4-00.fn01        163
 2  rmi4-00.fn03        164
 3  rmi4-00.fn11        165
 4  rmi4-00.fn11        166
 5  rmi4-00.fn30        167
0000:00:02.0                   e000-e03f
0000:00:1f.4                   efa0-efbf
0000:01:00.0                     d000-d07f
44  rmi4_smbus          160
acpi                      9
ACPI                             1800-1803     1804-1805     1808-180b     1810-1815     1850-1850     1880-189f
cascade             4
dma                            0080-008f
dma1                           0000-001f
dma2                           00c0-00df
dmar0                   120
dmar1                   121

Issue this command as a privileged user or all of the memory locations will be zeros.

`lspci`

This lspci utility comes from the pciutils package:

$ dpkg --search $(which lspci)
pciutils: /usr/bin/lspci

Each entry in the table will contain the following information. In order, they are:

slot
class
vendor
device
revision (optional)
programming interface (optional)

$ sudo lspci
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers (rev 08)
00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
00:04.0 Signal processing controller: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem (rev 08)
00:08.0 System peripheral: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #1 (rev f1)
00:1c.6 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #7 (rev f1)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #9 (rev f1)
00:1d.2 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #11 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point LPC Controller/eSPI Controller (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (4) I219-LM (rev 21)
01:00.0 3D controller: NVIDIA Corporation GP108M [GeForce MX150] (rev a1)
03:00.0 Network controller: Intel Corporation Wireless 8265 / 8275 (rev 78)
04:00.0 PCI bridge: Intel Corporation JHL6240 Thunderbolt 3 Bridge (Low Power) [Alpine Ridge LP 2016] (rev 01)
05:00.0 PCI bridge: Intel Corporation JHL6240 Thunderbolt 3 Bridge (Low Power) [Alpine Ridge LP 2016] (rev 01)
05:01.0 PCI bridge: Intel Corporation JHL6240 Thunderbolt 3 Bridge (Low Power) [Alpine Ridge LP 2016] (rev 01)
05:02.0 PCI bridge: Intel Corporation JHL6240 Thunderbolt 3 Bridge (Low Power) [Alpine Ridge LP 2016] (rev 01)
06:00.0 System peripheral: Intel Corporation JHL6240 Thunderbolt 3 NHI (Low Power) [Alpine Ridge LP 2016] (rev 01)
3c:00.0 USB controller: Intel Corporation JHL6240 Thunderbolt 3 USB 3.1 Controller (Low Power) [Alpine Ridge LP 2016] (rev 01)
3d:00.0 Non-Volatile memory controller: Intel Corporation SSD Pro 7600p/760p/E 6100p Series (rev 03)

Get more information about a specific device:

$ sudo lspci -s 3d:00.0 -v
3d:00.0 Non-Volatile memory controller: Intel Corporation SSD Pro 7600p/760p/E 6100p Series (rev 03) (prog-if 02 [NVM Express])
        Subsystem: Intel Corporation SSD Pro 7600p/760p/E 6100p Series [NVM Express]
        Flags: bus master, fast devsel, latency 0, IRQ 18, NUMA node 0, IOMMU group 17
        Memory at e9000000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/8 Maskable+ 64bit+
        Capabilities: [70] Express Endpoint, MSI 00
        Capabilities: [b0] MSI-X: Enable+ Count=16 Masked-
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [158] Secondary PCI Express
        Capabilities: [178] Latency Tolerance Reporting
        Capabilities: [180] L1 PM Substates
        Kernel driver in use: nvme
        Kernel modules: nvme

And the device’s kernel module in use:

$ sudo lspci -s 3d:00.0 -k
3d:00.0 Non-Volatile memory controller: Intel Corporation SSD Pro 7600p/760p/E 6100p Series (rev 03)
        Subsystem: Intel Corporation SSD Pro 7600p/760p/E 6100p Series [NVM Express]
        Kernel driver in use: nvme
        Kernel modules: nvme

Display all buses, bridges, devices and the connections between them as a tree (increase verbosity to include the names):

$ sudo lspci -vt
-[0000:00]-+-00.0  Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers
           +-02.0  Intel Corporation UHD Graphics 620
           +-04.0  Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem
           +-08.0  Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model
           +-14.0  Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller
           +-14.2  Intel Corporation Sunrise Point-LP Thermal subsystem
           +-16.0  Intel Corporation Sunrise Point-LP CSME HECI #1
           +-1c.0-[01]----00.0  NVIDIA Corporation GP108M [GeForce MX150]
           +-1c.6-[03]----00.0  Intel Corporation Wireless 8265 / 8275
           +-1d.0-[04-3c]----00.0-[05-3c]--+-00.0-[06]----00.0  Intel Corporation JHL6240 Thunderbolt 3 NHI (Low Power) [Alpine Ridge LP 2016]
           |                               +-01.0-[07-3b]--
           |                               \-02.0-[3c]----00.0  Intel Corporation JHL6240 Thunderbolt 3 USB 3.1 Controller (Low Power) [Alpine Ridge LP 2016]
           +-1d.2-[3d]----00.0  Intel Corporation SSD Pro 7600p/760p/E 6100p Series
           +-1f.0  Intel Corporation Sunrise Point LPC Controller/eSPI Controller
           +-1f.2  Intel Corporation Sunrise Point-LP PMC
           +-1f.3  Intel Corporation Sunrise Point-LP HD Audio
           +-1f.4  Intel Corporation Sunrise Point-LP SMBus
           \-1f.6  Intel Corporation Ethernet Connection (4) I219-LM

Increase the verbosity by adding up to three vs:

$ sudo lspci -v
$ sudo lspci -vv
$ sudo lspci -vvv

Show kernel modules for each device:

$ sudo lspci -k | tail
        Kernel driver in use: thunderbolt
        Kernel modules: thunderbolt
3c:00.0 USB controller: Intel Corporation JHL6240 Thunderbolt 3 USB 3.1 Controller (Low Power) [Alpine Ridge LP 2016] (rev 01)
        Subsystem: Device 2222:1111
        Kernel driver in use: xhci_hcd
        Kernel modules: xhci_pci
3d:00.0 Non-Volatile memory controller: Intel Corporation SSD Pro 7600p/760p/E 6100p Series (rev 03)
        Subsystem: Intel Corporation SSD Pro 7600p/760p/E 6100p Series [NVM Express]
        Kernel driver in use: nvme
        Kernel modules: nvme

`lsusb`

This lsusb utility comes from the usbutils package:

$ dpkg --search $(which lsusb)
usbutils: /usr/bin/lsusb

$ lsusb
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 0bda:0316 Realtek Semiconductor Corp. Card Reader
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 005: ID 06cb:009a Synaptics, Inc. Metallica MIS Touch Fingerprint Reader
Bus 001 Device 004: ID 5986:2113 Acer, Inc SunplusIT Integrated Camera
Bus 001 Device 003: ID 8087:0a2b Intel Corp. Bluetooth wireless interface
Bus 001 Device 002: ID 5986:1141 Acer, Inc Integrated IR Camera
Bus 001 Device 008: ID 047f:1200 Plantronics, Inc. Plantronics Calisto 7200
Bus 001 Device 006: ID 2386:432f Raydium Corporation Touch System
Bus 001 Device 009: ID 04d9:0169 Holtek Semiconductor, Inc. USB Keyboard
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Here it is as a tree structure:

$ lsusb -t
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 10000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
    |__ Port 3: Dev 2, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/12p, 480M
    |__ Port 1: Dev 9, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
    |__ Port 1: Dev 9, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
    |__ Port 2: Dev 8, If 2, Class=Audio, Driver=snd-usb-audio, 12M
    |__ Port 2: Dev 8, If 0, Class=Audio, Driver=snd-usb-audio, 12M
    |__ Port 2: Dev 8, If 3, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 2: Dev 8, If 1, Class=Audio, Driver=snd-usb-audio, 12M
    |__ Port 5: Dev 2, If 1, Class=Video, Driver=uvcvideo, 480M
    |__ Port 5: Dev 2, If 0, Class=Video, Driver=uvcvideo, 480M
    |__ Port 7: Dev 3, If 0, Class=Wireless, Driver=btusb, 12M
    |__ Port 7: Dev 3, If 1, Class=Wireless, Driver=btusb, 12M
    |__ Port 8: Dev 4, If 1, Class=Video, Driver=uvcvideo, 480M
    |__ Port 8: Dev 4, If 0, Class=Video, Driver=uvcvideo, 480M
    |__ Port 9: Dev 5, If 0, Class=Vendor Specific Class, Driver=, 12M
    |__ Port 10: Dev 6, If 0, Class=Human Interface Device, Driver=usbhid, 12M

Search by vendor ID and product ID:

$ lsusb -d 04d9:0169
Bus 001 Device 009: ID 04d9:0169 Holtek Semiconductor, Inc. USB Keyboard

And get more information:

$ sudo lsusb -vd 04d9:0169 | head
can't get debug descriptor: Resource temporarily unavailable

Bus 001 Device 009: ID 04d9:0169 Holtek Semiconductor, Inc. USB Keyboard
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.10
  bDeviceClass            0
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0         8

Search by bus number only:

$ lsusb -s 2:
Bus 002 Device 002: ID 0bda:0316 Realtek Semiconductor Corp. Card Reader
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub

Search by bus number and device number:

$ lsusb -s 1:4
Bus 001 Device 004: ID 5986:2113 Acer, Inc SunplusIT Integrated Camera

And then get more information about it (-v):

$ sudo lsusb -vs 1:4 | head

Bus 001 Device 004: ID 5986:2113 Acer, Inc SunplusIT Integrated Camera
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.01
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64

Note that when using the verbose flag (-v) that it’s necessary to have escalated privileges (sudo).

Service Management

`SysV`

Managed by /sbin/init.

runlevels

Every runlevel has associated scripts in /etc/rc[0-6].d/, and each script is prefaces with an S (start) or a K (kill or stop).

Since one or more runlevel can have the same script (i.e, the same behavior), these scripts are just symlinks to the associated scripts in /etc/init.d/.

runlevel 0
- system shutdown
runlevel 1
- also, s or single
- single user mode
- no network and other non-essential capabilities (maintenance mode)
runlevel 2, 3 or 4
- multi-user mode
- users can log in by console or network
- runlevels 2 and 4 are not often used
runlevel 5
- multi-user mode
- network and the graphical mode login
runlevel 6
- system restart

Runlevels can be changed using either init or telinit.

Both of the following commands will change to single-user mode:

sudo init 1
sudo telinit 1

So, no need to reboot when changing runlevels.

The runlevel command will print the previous and current SysV runlevel:

$ runlevel
N 5

Here, N means that it was booted into runlevel 5. If it had been in a previous runlevel, the output would be something like 3 5.

Reload daemon configuration every time /etc/inittab has been modified:

$ sudo telinit q

This is equivalent to systemctl daemon-reload.

`/etc/inittab`

Runlevels are determined by a kernel parameter or in /etc/inittab:

A typical /etc/inittab looks like the following:

/etc/inittab

# Default runlevel
id:3:initdefault:

# Configuration script executed during boot
si::sysinit:/etc/init.d/rcS

# Action taken on runlevel S (single user)
~:S:wait:/sbin/sulogin

# Configuration for each execution level
l0:0:wait:/etc/init.d/rc 0
l1:1:wait:/etc/init.d/rc 1
l2:2:wait:/etc/init.d/rc 2
l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4
l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6

# Action taken upon ctrl+alt+del keystroke
ca::ctrlaltdel:/sbin/shutdown -r now

# Enable consoles for runlevels 2 and 3
1:23:respawn:/sbin/getty tty1 VC linux
2:23:respawn:/sbin/getty tty2 VC linux
3:23:respawn:/sbin/getty tty3 VC linux
4:23:respawn:/sbin/getty tty4 VC linux

# For runlevel 3, also enable serial
# terminals ttyS0 and ttyS1 (modem) consoles
S0:3:respawn:/sbin/getty -L 9600 ttyS0 vt320
S1:3:respawn:/sbin/mgetty -x0 -D ttyS1

If -a is placed before the option at the line with ctrlaltdel in /etc/inittab, then users can restart the machine by pressing Ctrl+Alt+Del, but only for the users whitelisted in /etc/shutdown.allow.
# Action taken upon ctrl+alt+del keystroke
ca::ctrlaltdel:/sbin/shutdown -r now

`systemd`

Services

Services are referred to as units by systemd.

There are seven types of units:

service
socket
device
mount
automount
target
snapshot

The configuration files for every unit can be found in /lib/systemd/system/.

`systemctl`

systemd and its service manager are managed by systemctl.

Its most common actions are:

systemctl start UNIT.service
systemctl stop UNIT.service
systemctl restart UNIT.service
systemctl status UNIT.service
systemctl is-active UNIT.service
systemctl enable UNIT.service
systemctl disable UNIT.service
systemctl is-enabled UNIT.service

systemd system targets are groupings of units that are managed as a single unit, akin to runlevels. To manage them:

$ sudo systemctl isolate multi-user.target
or
$ sudo systemctl isolate runlevel3.target

The multi-user.target unit, for example, combines all units required by the multi-user system environment. It is similar to the runlevel number 3 in a system utilizing SysV.

Note the backwards-compatibility with SysV: runlevel3.target. There is a similar runlevel target for each system target.

systemd does not, however, support the /etc/inittab file. An analogous behavior in systemd would be to set a kernel parameter such as systemd.unit=multi-user.target or to make it permanent by changing the bootloader configuration.

Another way to change the system target is to modify the soft link /etc/systemd/system/default.target:

$ readlink -f /etc/systemd/system/default.target
/usr/lib/systemd/system/multi-user.target
$ ls -l /etc/systemd/system/default.target
lrwxrwxrwx 1 root root 37 Jan  2 17:38 /etc/systemd/system/default.target -> /lib/systemd/system/multi-user.target
$ systemctl get-default
multi-user.target
$ sudo systemctl set-default graphical.target

To see all available units and their state (i.e., enabled, disabled, masked, etc.):

$ systemctl list-unit-files

To restrict to a certain type:

systemctl list-unit-files --type=service

The same can be done for listing the current units. Simple s/list-unit-files/list-units in the two previous examples.

# systemctl suspend
# systemctl hibernate
# systemctl reboot

Mount Units

View all customized mount points:

$ systemctl -t mount list-units

Recall that systemd will create mount units for all mount points defined in /etc/fstab.

However, when manually creating a mount point, systemd will also automatically generate a mount unit file, as well as create entries in the /proc pseudo-filesystem.

Check this out:

$ mkdir src targ
$ touch src/foo
$ sudo mount --bind src targ
$ mount
/dev/mapper/kilgore--trout--vg-root on /home/btoll/targ type ext4 (rw,relatime,errors=remount-ro)
$ systemctl -t mount list-units
  UNIT                          LOAD   ACTIVE SUB     DESCRIPTION
  -.mount                       loaded active mounted Root Mount
  boot-efi.mount                loaded active mounted /boot/efi
  boot.mount                    loaded active mounted /boot
  dev-hugepages.mount           loaded active mounted Huge Pages File System
  dev-mqueue.mount              loaded active mounted POSIX Message Queue File System
  home-btoll-targ.mount         loaded active mounted /home/btoll/targ
  ...
$ cat /proc/self/mountinfo
...
586 29 253:1 /home/btoll/src /home/btoll/targ rw,relatime shared:1 - ext4 /dev/mapper/kilgore--trout--vg-root rw,errors=remount-ro
$ cat /proc/self/mounts
...
/dev/mapper/kilgore--trout--vg-root /home/btoll/targ ext4 rw,relatime,errors=remount-ro 0 0

Of course, they are removed when the mount point is unmounted.

Powering Off

All of the following can be use to power off the system:

halt
poweroff
shutdown
- shutdown [option] time [message]
- all processes receive SIGTERM and then SIGKILL
- if neither -r or -h is given, it will change to runlevel 1 (single-user mode)
- its message parameter gets sent to all terminals of logged-in users
systemctl isolate halt
systemctl isolate poweroff

Also, note that all of the following are soft links to /usr/bin/systemctl:

$ readlink -f /usr/sbin/{halt,poweroff,shutdown,reboot}
/usr/bin/systemctl
/usr/bin/systemctl
/usr/bin/systemctl
/usr/bin/systemctl

`Upstart`

Developed by Ubuntu to parallelize the system initialization process, Ubuntu stopped using Upstart in 2015.

Initialization scripts are in /etc/init/.

List services, their state, and, if possible, the PID:

# initctl list

Initiate a sixth virtual terminal:

# start tty6

And get its current state:

# status tty6

Stop it:

# stop tty6

Upstart does not support /etc/inittab, but it does support init and telinit.

Kernel Ring Buffer

Dump the kernel ring buffer to view the system initialization logs.

`dmesg`

list all initialization logs:
- dmesg
tail the kernel ring buffer:
- dmesg -w or dmesg --follow

`journalctl`

list all initialization logs:
- journalctl -k or journalctl --dmesg
tail the kernel ring buffer:
- journalctl --dmesg --follow

Note that you can do more interesting stuff with journalctl such as view recent boot logs:

journalctl --list-boots # list all boots journalctl --boot=0 # the last boot journalctl --boot=2 # the second-to-last boot

Summary

Continue your journey with the second installment in this titillating series, On the LPIC-1 Exam 101: Linux Installation and Package Management.

On the LPIC-1 Exam 101: System Architecture

Exam Details

Topic 101: System Architecture

Block Devices and Hardware Settings

blkid

lsblk

lscpu

lsdev

lspci

lsusb