How to use Udevadm and Useful commands to fetch Hardware info USB info Monitor info Memory etc

The following commands are useful for the daily work in the Linux Machine. These commands are executed on Ubuntu Linux 14.04 32-bit Machine.

Command #1 : How to get the distribution of Linux Machine?
lsb_release - print distribution-specific information

root@m:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.4 LTS
Release:        14.04
Codename:       trusty

Command #2 : How to get the list of USB devices ?
lsusb - list USB devices

root@m:~# lsusb
Bus 002 Device 002: ID 0b95:1780 ASIX Electronics Corp. AX88178
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 002: ID 03f9:0100 KeyTronic Corp. KT-2001 Keyboard
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

Command #3 : How to get the BIOS,  Hardware details, Manufacturer, BIOS release date etc. ?

dmidecode - DMI table decoder

This table contains a description of the system's hardware components, as well as other useful pieces of information such as serial numbers and BIOS revision

Keyword               Types
──────────────────
bios                    0, 13
system               1, 12, 15, 23, 32
baseboard          2, 10, 41
chassis               3
processor           4
memory             5, 6, 16, 17
cache                 7
connector          8
slot                    9

Examples:
root@m:~# dmidecode -t 1     -> t indicates type
# dmidecode 2.12
SMBIOS 2.5 present.
Handle 0x0100, DMI type 1, 27 bytes
System Information
        Manufacturer: Dell Inc.
        Product Name: SUPER JET
        Version: Not Specified
        Serial Number: 8GCRXY
        UUID: 4MUNI-5200-1043-84422
        Wake-up Type: APM Timer
        SKU Number: Not Specified
        Family: Not Specified

root@m:~# dmidecode -t 4
# dmidecode 2.12
SMBIOS 2.5 present.
Handle 0x0400, DMI type 4, 40 bytes
Processor Information
        Socket Designation: CPU
        Type: Central Processor
        Family: Core 2 Duo
        Manufacturer: Intel

Get HW information about BIOS         :   dmidecode -t bios
Get HW information about System       :   dmidecode -t system
Get HW information about baseboard    :   dmidecode -t baseboard
Get HW information about chassis      :   dmidecode -t chassis

Command #4 : How to configure (set/get), list, test input devices of the Linux Machine ?

xinput -  is a utility to list available input devices, query information about a device and change input device settings

root@m:~# xinput   or xinput --list

⎡ Virtual core pointer                          id=2    [master pointer  (3)]

⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]

⎜   ↳ eGalax Inc. USB TouchController           id=9    [slave  pointer  (2)]

⎜   ↳ eGalax Inc. USB TouchController Pen       id=8    [slave  pointer  (2)]

⎣ Virtual core keyboard                         id=3    [master keyboard (2)]

    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]

    ↳ Dell Dell USB Keyboard                    id=11   [slave  keyboard (3)]

    ↳ Wincor Nixdorf BEETLE /Express Composite Device   id=10   [slave  keyboard (3)]

    ↳ Power Button                              id=7    [slave  keyboard (3)]

    ↳ Power Button                              id=6    [slave  keyboard (3)]

How to Get the Properties of particular Device Using the Device ID?

root@m:~# xinput --list-props 11

Device 'Dell Dell USB Keyboard':

        Device Enabled (114):   0

        Coordinate Transformation Matrix (116): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

        Device Product ID (232):        16700, 8453

        Device Node (233):      "/dev/input/event3"

Command #5 : How to list hardware in the Linux Machine ?

lshw - list hardware

lshw is a small tool to extract detailed information on the hardware configuration of the machine. It can report exact memory configuration, firmware version, mainboard configuration, CPU version and speed, cache configuration, bus speed, etc.

EXAMPLES

       lshw -short

              Lists hardware in a compact format.

       lshw -class disk -class storage

              Lists all disks and storage controllers in the system.

       lshw -html -class network

              Lists all network interfaces in HTML.

       lshw -disable dmi

              Don't use DMI to detect hardware.

root@m:~# lshw -c disk

  *-disk

       description: ATA Disk

       product: SanDisk SSD U100

       physical id: 0.0.0

       bus info: scsi@2:0.0.0

       logical name: /dev/sda

       version: 10.5

       serial: 132535401384

       size: 59GiB (64GB)

       capabilities: partitioned partitioned:dos

root@m:~# lshw -short

H/W path        Device     Class      Description

=================================================

                           system     DELL 15 D525,2GB,HDD (To Be Filled By O.E.M.)

/0                         bus        PD359

/0/0                       memory     64KiB BIOS

/0/4                       processor  Intel(R) Atom(TM) CPU D525   @ 1.80GHz

/0/4/5                     memory     48KiB L1 cache

/0/4/6                     memory     1MiB L2 cache

/0/4/0.1                   processor  Logical CPU

/0/4/0.2                   processor  Logical CPU

/0/4/0.3                   processor  Logical CPU

/0/4/0.4                   processor  Logical CPU

/0/d                       memory     4GiB System Memory

/0/d/0                     memory     4GiB SODIMM DDR3 Synchronous 800 MHz (1.2 ns)

/0/1                       processor

/0/1/0.1                   processor  Logical CPU

/0/1/0.2                   processor  Logical CPU

/0/1/0.3                   processor  Logical CPU

/0/1/0.4                   processor  Logical CPU

/0/100                     bridge     Atom Processor D4xx/D5xx/N4xx/N5xx DMI Bridge

/0/100/2                   display    Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller

/0/100/2.1                 display    Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller

/0/100/1a                  bus        82801H (ICH8 Family) USB UHCI Controller #4

/0/100/1a.1                bus        82801H (ICH8 Family) USB UHCI Controller #5

/0/100/1a.7                bus        82801H (ICH8 Family) USB2 EHCI Controller #2

/0/100/1c                  bridge     82801H (ICH8 Family) PCI Express Port 1

/0/100/1c.4                bridge     82801H (ICH8 Family) PCI Express Port 5

/0/100/1c.4/0   eth0       network    RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller

/0/100/1d                  bus        82801H (ICH8 Family) USB UHCI Controller #1

/0/100/1d.1                bus        82801H (ICH8 Family) USB UHCI Controller #2

/0/100/1d.2                bus        82801H (ICH8 Family) USB UHCI Controller #3

/0/100/1d.7                bus        82801H (ICH8 Family) USB2 EHCI Controller #1

/0/100/1e                  bridge     82801 Mobile PCI Bridge

/0/100/1f                  bridge     82801HM (ICH8M) LPC Interface Controller

/0/100/1f.1                storage    82801HM/HEM (ICH8M/ICH8M-E) IDE Controller

/0/100/1f.2                storage    82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [IDE mode]

/0/100/1f.3                bus        82801H (ICH8 Family) SMBus Controller

/0/2            scsi2      storage

/0/2/0.0.0      /dev/sda   disk       64GB SanDisk SSD U100

/0/2/0.0.0/1    /dev/sda1  volume     243MiB Linux filesystem partition

/0/2/0.0.0/2    /dev/sda2  volume     59GiB Extended partition

/0/2/0.0.0/2/5  /dev/sda5  volume     59GiB Linux LVM Physical Volume partition

/1                         power      ----------------------------------------

/2                         power      9NA0651264

Command #6 : How to get the monitor model information in Linux ?

get-edid | parse-edid

get-edid, parse-edid - read-edid tools to retrieve and interpret monitor specifications using the VESA VBE DDC protocol

(or)  

grep -i "monitor name" /var/log/Xorg.*.log 

Command #7 : How to check disk space in Linux ?

df - report file system disk space usage
df displays the amount of disk space available on the file system containing each file name argument

root@m:~# df -h

Filesystem      Size  Used Avail Use% Mounted on
udev            980M  4.0K  980M   1% /dev
tmpfs           198M  3.6M  195M   2% /run
/dev/dm-1        20G  9.7G  9.3G  51% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
none            5.0M   12K  5.0M   1% /run/lock
none            990M     0  990M   0% /run/shm
none            100M  4.0K  100M   1% /run/user

root@m:~# df /dev/sda

Filesystem     1K-blocks  Used Available Use% Mounted on

udev             1003444     4   1003440   1% /dev

root@m:~# df /dev/sda

Filesystem     1K-blocks  Used Available Use% Mounted on

udev             1003444     4   1003440   1% /dev

root@m:~# df -h /dev/sda

Filesystem      Size  Used Avail Use% Mounted on

udev            980M  4.0K  980M   1% /dev

root@m:~# df -a

Filesystem     1K-blocks     Used Available Use% Mounted on

sysfs                  0        0         0    - /sys

proc                   0        0         0    - /proc

udev             1003444        4   1003440   1% /dev

devpts                 0        0         0    - /dev/pts

tmpfs             202744     3640    199104   2% /run

/dev/dm-1       20039548 10076208   9742036  51% /

none                   4        0         4   0% /sys/fs/cgroup

none                   0        0         0    - /sys/fs/fuse/connections

none                   0        0         0    - /sys/kernel/debug

none                   0        0         0    - /sys/kernel/security

none                5120       12      5108   1% /run/lock

none             1013704        0   1013704   0% /run/shm

none              102400        4    102396   1% /run/user

none                   0        0         0    - /sys/fs/pstore

/dev/dm-1       20039548 10076208   9742036  51% /appl/lib

rpc_pipefs             0        0         0    - /run/rpc_pipefs

systemd                0        0         0    - /sys/fs/cgroup/systemd

nfsd                   0        0         0    - /proc/fs/nfsd

proc                   0        0         0    - /appl/proc

root@m:~# df -a -h

Filesystem      Size  Used Avail Use% Mounted on

sysfs              0     0     0    - /sys

proc               0     0     0    - /proc

udev            980M  4.0K  980M   1% /dev

devpts             0     0     0    - /dev/pts

tmpfs           198M  3.6M  195M   2% /run

/dev/dm-1        20G  9.7G  9.3G  51% /

none            4.0K     0  4.0K   0% /sys/fs/cgroup

none               0     0     0    - /sys/fs/fuse/connections

none               0     0     0    - /sys/kernel/debug

none               0     0     0    - /sys/kernel/security

none            5.0M   12K  5.0M   1% /run/lock

none            990M     0  990M   0% /run/shm

none            100M  4.0K  100M   1% /run/user

none               0     0     0    - /sys/fs/pstore

/dev/dm-1        20G  9.7G  9.3G  51% /appl/lib

rpc_pipefs         0     0     0    - /run/rpc_pipefs

systemd            0     0     0    - /sys/fs/cgroup/systemd

nfsd               0     0     0    - /proc/fs/nfsd

proc               0     0     0    - /appl/proc

root@m:~# df --total

Filesystem     1K-blocks     Used Available Use% Mounted on

udev             1003444        4   1003440   1% /dev

tmpfs             202744     3640    199104   2% /run

/dev/dm-1       20039548 10076264   9741980  51% /

none                   4        0         4   0% /sys/fs/cgroup

none                5120       12      5108   1% /run/lock

none             1013704        0   1013704   0% /run/shm

none              102400        4    102396   1% /run/user

total           22366964 10079924  12065736  46% -

Command #8 :  How to list the open files in Linux?

lsof - list of open files.
In Unix, every thing is file. Using lsof command, we can list the open files.

FD – Represents the file descriptor. Some of the values of FDs are,
cwd – Current Working Directory
txt – Text file
mem – Memory mapped file
mmap – Memory mapped device
NUMBER – Represent the actual file descriptor. The character after the number i.e ‘1u’, represents the mode in which the file is opened. r for read, w for write, u for read and write.

TYPE – Specifies the type of the file. Some of the values of TYPEs are,
REG – Regular File
DIR – Directory
FIFO – First In First Out

CHR – Character special file

How to list process which opened the file?

root@m:~# lsof /var/log/kern.log
COMMAND    PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME

rsyslogd 11086 syslog    5w   REG  252,0    25850  314 /var/log/kern.log

How to list opened files under directory? (+D)

root@m:~# lsof +D /var/log
COMMAND    PID   USER   FD   TYPE DEVICE SIZE/OFF   NODE NAME
cupsd      464   root    4u   REG  252,0        0 136301 /var/log/cups/access_log
cupsd      464   root    5u   REG  252,0        0 156937 /var/log/cups/error_log
cupsd      464   root    6u   REG  252,0        0 156938 /var/log/cups/page_log
smbd       577   root    2w   REG  252,0        0 144792 /var/log/samba/log.smbd
smbd       577   root   34w   REG  252,0        0 144792 /var/log/samba/log.smbd
smbd       621   root    2w   REG  252,0        0 144792 /var/log/samba/log.smbd
smbd       621   root   28w   REG  252,0        0 144792 /var/log/samba/log.smbd
elousbd   2181   root    2w   REG  252,0     1950   2380 /var/log/rc.local.log
elousbd   2181   root    3u   REG  252,0      114 156946 /var/log/elo-usb/EloUsbErrorLog.txt
nmbd      2604   root    2w   REG  252,0     2162 144797 /var/log/samba/log.nmbd
nmbd      2604   root   18w   REG  252,0     2162 144797 /var/log/samba/log.nmbd
rsyslogd 11086 syslog    1w   REG  252,0   700207    330 /var/log/auth.log
rsyslogd 11086 syslog    2w   REG  252,0    34882    310 /var/log/syslog
rsyslogd 11086 syslog    5w   REG  252,0    25850    314 /var/log/kern.log

Xorg     31401   root    0w   REG  252,0   140409    861 /var/log/Xorg.1.log

How to list opened files based on process name?

root@m:~# lsof -c sshd

sshd     2517 root  cwd    DIR      252,0     4096         2 /

sshd     2517 root  rtd    DIR      252,0     4096         2 /

sshd     2517 root  txt    REG      252,0   834680     21216 /usr/sbin/sshd

sshd     2517 root  mem    REG      252,0    46812    134784 /lib/i386-linux-gnu/libnss_files-2.19.so

sshd     2517 root  mem    REG      252,0    42668    134778 /lib/i386-linux-

sshd    22635 root    4u  unix 0xf5da0b00      0t0 138945568 socket

sshd    22635 root    5r  FIFO        0,8      0t0 138944997 pipe

sshd    22635 root    6w  FIFO        0,8      0t0 138944997 pipe

sshd    22635 root    8u   CHR        5,2      0t0      9473 /dev/ptmx

sshd    22635 root   10u   CHR        5,2      0t0      9473 /dev/ptmx

sshd    22635 root   11u   CHR        5,2      0t0      9473 /dev/ptmx

How to list all Network connections?

root@m:~# lsof -i

How to list all TCP/UDP connections?

root@m:~# lsof -i tcp

COMMAND     PID   USER   FD   TYPE    DEVICE SIZE/OFF NODE NAME

cupsd       464   root   10u  IPv6     11515      0t0  TCP localhost:ipp (LISTEN)

cupsd       464   root   11u  IPv4     11516      0t0  TCP localhost:ipp (LISTEN)

smbd        577   root   30u  IPv6     11540      0t0  TCP *:microsoft-ds (LISTEN)

smbd        577   root   31u  IPv6     11541      0t0  TCP *:netbios-ssn (LISTEN)

smbd        577   root   32u  IPv4     11542      0t0  TCP *:microsoft-ds (LISTEN)

smbd        577   root   33u  IPv4     11543      0t0  TCP *:netbios-ssn (LISTEN)

rpcbind     613   root    8u  IPv4      8908      0t0  TCP *:sunrpc (LISTEN)

rpcbind     613   root   11u  IPv6      8911      0t0  TCP *:sunrpc (LISTEN)

rpc.statd   719  statd    9u  IPv4     11603      0t0  TCP *:34794 (LISTEN)

rpc.statd   719  statd   11u  IPv6     11609      0t0  TCP *:55775 (LISTEN)

xinetd     1019   root    6u  IPv4      9176      0t0  TCP *:ftp (LISTEN)

portcommu  1124   root   10u  IPv4     11887      0t0  TCP *:2291 (LISTEN)

sshd       2517   root    3u  IPv4     14006      0t0  TCP *:ssh (LISTEN)

sshd       2517   root    4u  IPv6     14008      0t0  TCP *:ssh (LISTEN)

root@m:~# lsof -i udp

COMMAND    PID  USER   FD   TYPE   DEVICE SIZE/OFF NODE NAME

rpcbind    613  root    6u  IPv4     8904      0t0  UDP *:sunrpc

rpcbind    613  root    7u  IPv4     8907      0t0  UDP *:783

rpcbind    613  root    9u  IPv6     8909      0t0  UDP *:sunrpc

rpcbind    613  root   10u  IPv6     8910      0t0  UDP *:783

rpc.statd  719 statd    5u  IPv4    12547      0t0  UDP localhost:895

rpc.statd  719 statd    8u  IPv4    11600      0t0  UDP *:52247

rpc.statd  719 statd   10u  IPv6    11606      0t0  UDP *:60550

cups-brow  863  root    8u  IPv4    10767      0t0  UDP *:ipp

xinetd    1019  root    5u  IPv4     9175      0t0  UDP *:tftp

How to list all files associated with process ID?

root@m:~# lsof -p 613

COMMAND PID USER   FD   TYPE     DEVICE SIZE/OFF   NODE NAME

rpcbind 613 root  cwd    DIR      252,0     4096      2 /

rpcbind 613 root  rtd    DIR      252,0     4096      2 /

rpcbind 613 root  txt    REG      252,0    42920  12332 /sbin/rpcbind

rpcbind 613 root  mem    REG      252,0    42668 134778 /lib/i386-linux-gnu/libnss_nis-2.19.so

rpcbind 613 root  mem    REG      252,0    30560 134770 /lib/i386-linux-gnu/libnss_compat-2.19.so

rpcbind 613 root  mem    REG      252,0    13856 134779 /lib/i386-linux-gnu/libdl-2.19.so

rpcbind 613 root  mem    REG      252,0    92036 134788 /lib/i386-linux-gnu/libnsl-2.19.so

How to list all files associated with port number?

root@m:~# lsof -i :19578

COMMAND   PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME

dhclient 2362 root   20u  IPv4  11193      0t0  UDP *:19578

How to list all files under username?

root@m:~# lsof -u muni

How to kill all files under username?

root@m:~# kill -9 `lsof -t -u muni`

 ‘-t’ option to list output only the process id of the process

What is Udev and How to use the Udev rules in Linux?

Udev - Manages the devices dynamically.

This is the device management tool runs in the user space to manages (creates/remove) the devices dynamically. Present from 2.6 kernel on wards and it runs in user space.
udevd is the process, it manages the device nodes (permissions, symlinks, name) in /dev directory.

For example: If we attach an USB device, user can set permissions that it can accessible to specific user etc or run specific script.

How it works?
 Step 1: Attach a USB disk.

 Step 2:  Kernel detects it and sysfs is populated with device details like serial number, vendor,
               port etc.. in /sys/ directory.

 Step 3: Kernel will send an uevent and this event shall be received by Udev
              (udevd process listening for uevents) .

 Step 4: Then udev checks in the sysfs (file system) whether it have an rule corresponding for
               this uevent. The rules are present in the /etc/udev/rules.d/*.rules.

 Step 5:  udevd will check all rules present under /etc/udev/rules.d/*.rules and identify this device                    matches with any rules present in this directory.
               If it matches the rule, then it performs the actions (Setting the permissions,
               run custom script, symlink etc.)

How to find the information using udevadm tool?
udevadm:  is the udev management tool.

Commands :

udevadm info options
udevadm trigger [options]
udevadm settle [options]
udevadm control command
udevadm monitor [options]
udevadm test [options] devpath

Examples:

root@m:~# udevadm info
Usage: udevadm info OPTIONS
  --query=<type>             query device information:
      name                     name of device node
      symlink                  pointing to node
      path                     sys device path
      property                 the device properties
      all                      all values
  --path=<syspath>           sys device path used for query or attribute walk
  --name=<name>              node or symlink name used for query or attribute walk
  --root                     prepend dev directory to path names
  --attribute-walk           print all key matches while walking along the chain
                             of parent devices
  --device-id-of-file=<file> print major:minor of device containing this file
  --export                   export key/value pairs
  --export-prefix            export the key name with a prefix
  --export-db                export the content of the udev database
  --cleanup-db               cleanup the udev database
  --help

root@m:~# fdisk -l /dev/sda

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000bb738

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048    34613373    17305663   da  Non-FS data

/dev/sda4   *    34613374   156248189    60817408   fd  

root@m:~# udevadm info -a /dev/sda

Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.

  looking at device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda':
    KERNEL=="sda"
    SUBSYSTEM=="block"
    DRIVER==""
    ATTR{ro}=="0"
    ATTR{size}=="488397168"
    ATTR{stat}=="  136370   841647 122415922  2097420    50871    33096   613279   317380        0   764248  2414756"
    ATTR{range}=="16"
    ATTR{discard_alignment}=="0"
    ATTR{events}==""
    ATTR{ext_range}=="256"
    ATTR{events_poll_msecs}=="-1"
    ATTR{alignment_offset}=="0"
    ATTR{inflight}=="       0        0"
    ATTR{removable}=="0"
    ATTR{capability}=="50"
    ATTR{events_async}==""

  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0':
    KERNELS=="0:0:0:0"
    SUBSYSTEMS=="scsi"
    DRIVERS=="sd"
    ATTRS{rev}=="19.0"
    ATTRS{type}=="0"
    ATTRS{scsi_level}=="6"
    ATTRS{model}=="WDC WD2500AAKX-7"
    ATTRS{state}=="running"
    ATTRS{queue_type}=="simple"
    ATTRS{iodone_cnt}=="0x35107"
    ATTRS{iorequest_cnt}=="0x35b96"
    ATTRS{queue_ramp_up_period}=="120000"
    ATTRS{device_busy}=="0"
    ATTRS{evt_capacity_change_reported}=="0"
    ATTRS{timeout}=="30"
    ATTRS{evt_media_change}=="0"
    ATTRS{ioerr_cnt}=="0x67"
    ATTRS{queue_depth}=="31"
    ATTRS{vendor}=="ATA     "
    ATTRS{evt_soft_threshold_reached}=="0"
    ATTRS{device_blocked}=="0"
    ATTRS{evt_mode_parameter_change_reported}=="0"
    ATTRS{evt_lun_change_reported}=="0"
    ATTRS{evt_inquiry_change_reported}=="0"
    ATTRS{iocounterbits}=="32"
    ATTRS{eh_timeout}=="10"

  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0':
    KERNELS=="target0:0:0"
    SUBSYSTEMS=="scsi"
    DRIVERS==""

  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0':
    KERNELS=="host0"
    SUBSYSTEMS=="scsi"
    DRIVERS==""

  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1':
    KERNELS=="ata1"
    SUBSYSTEMS==""
    DRIVERS==""

  looking at parent device '/devices/pci0000:00/0000:00:1f.2':
    KERNELS=="0000:00:1f.2"
    SUBSYSTEMS=="pci"
    DRIVERS=="ahci"
    ATTRS{irq}=="51"
    ATTRS{subsystem_vendor}=="0x1028"
    ATTRS{broken_parity_status}=="0"
    ATTRS{class}=="0x010400"
    ATTRS{consistent_dma_mask_bits}=="64"
    ATTRS{dma_mask_bits}=="64"
    ATTRS{local_cpus}=="ff"
    ATTRS{device}=="0x2822"
    ATTRS{enable}=="1"
    ATTRS{msi_bus}==""
    ATTRS{local_cpulist}=="0-7"
    ATTRS{vendor}=="0x8086"
    ATTRS{subsystem_device}=="0x02fb"
    ATTRS{d3cold_allowed}=="1"

  looking at parent device '/devices/pci0000:00':
    KERNELS=="pci0000:00"
    SUBSYSTEMS==""

root@m:~# udevadm info --export-db > entire_udev_database
root@m:~# vim entire_udev_database
P: /devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda
N: sda
S: disk/by-id/ata-WDC_WD2500AAKX-75U6AA0_WD-WCC2F1095181
S: disk/by-id/wwn-0x50014ee207ecee4d
S: rootdisk
E: DEVLINKS=/dev/disk/by-id/ata-WDC_WD2500AAKX-75U6AA0_WD-WCC2F1095181 /dev/disk/by-id/wwn-0x50014ee207ecee4d /dev/rootdisk
E: DEVNAME=/dev/sda
E: DEVPATH=/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda
E: DEVTYPE=disk
E: ID_ATA=1
E: ID_ATA_DOWNLOAD_MICROCODE=1
E: ID_ATA_FEATURE_SET_HPA=1
E: ID_ATA_FEATURE_SET_HPA_ENABLED=1
E: ID_ATA_FEATURE_SET_PM=1
E: ID_ATA_FEATURE_SET_PM_ENABLED=1
E: ID_ATA_FEATURE_SET_PUIS=1
E: ID_ATA_FEATURE_SET_PUIS_ENABLED=0
E: ID_ATA_FEATURE_SET_SECURITY=1
E: ID_ATA_FEATURE_SET_SECURITY_ENABLED=0
E: ID_ATA_FEATURE_SET_SECURITY_ENHANCED_ERASE_UNIT_MIN=44
E: ID_ATA_FEATURE_SET_SECURITY_ERASE_UNIT_MIN=44
E: ID_ATA_FEATURE_SET_SECURITY_FROZEN=1
E: ID_ATA_FEATURE_SET_SMART=1
E: ID_ATA_FEATURE_SET_SMART_ENABLED=1
E: ID_ATA_SATA=1
E: ID_ATA_SATA_SIGNAL_RATE_GEN1=1
E: ID_ATA_SATA_SIGNAL_RATE_GEN2=1
E: ID_ATA_WRITE_CACHE=1
E: ID_ATA_WRITE_CACHE_ENABLED=1
E: ID_BUS=ata
E: ID_MODEL=WDC_WD2500AAKX-75U6AA0
E: ID_MODEL_ENC=WDC\x20WD2500AAKX-75U6AA0\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
E: ID_PART_TABLE_TYPE=dos
E: ID_REVISION=19.01H19
E: ID_SERIAL=WDC_WD2500AAKX-75U6AA0_WD-WCC2F1095181
E: ID_SERIAL_SHORT=WD-WCC2F1095181
E: ID_TYPE=disk
E: ID_WWN=0x50014ee207ecee4d
E: ID_WWN_WITH_EXTENSION=0x50014ee207ecee4d
E: MAJOR=8
E: MINOR=0
E: SUBSYSTEM=block
E: UDISKS_IGNORE=1
E: USEC_INITIALIZED=4665
E: nomdmonddf=1
E: nomdmonisw=1

root@m:~# udevadm info -a /dev/ttyS4

  looking at device '/devices/platform/serial8250/tty/ttyS4':
    KERNEL=="ttyS4"
    SUBSYSTEM=="tty"
    DRIVER==""
    ATTR{irq}=="0"
    ATTR{line}=="4"
    ATTR{port}=="0x0"
    ATTR{type}=="0"
    ATTR{flags}=="0x0"
    ATTR{iomem_base}=="0x0"
    ATTR{custom_divisor}=="0"
    ATTR{iomem_reg_shift}=="0"
    ATTR{uartclk}=="0"
    ATTR{xmit_fifo_size}=="0"
    ATTR{close_delay}=="50"
    ATTR{closing_wait}=="3000"
    ATTR{io_type}=="0"

  looking at parent device '/devices/platform/serial8250':
    KERNELS=="serial8250"
    SUBSYSTEMS=="platform"
    DRIVERS=="serial8250"

  looking at parent device '/devices/platform':
    KERNELS=="platform"
    SUBSYSTEMS==""
    DRIVERS==""

root@m:~# udevadm info --attribute-walk /dev/ttyS4
  looking at device '/devices/platform/serial8250/tty/ttyS4':
    KERNEL=="ttyS4"
    SUBSYSTEM=="tty"
    DRIVER==""
    ATTR{irq}=="0"
    ATTR{line}=="4"
    ATTR{port}=="0x0"
    ATTR{type}=="0"
    ATTR{flags}=="0x0"
    ATTR{iomem_base}=="0x0"
    ATTR{custom_divisor}=="0"
    ATTR{iomem_reg_shift}=="0"
    ATTR{uartclk}=="0"
    ATTR{xmit_fifo_size}=="0"
    ATTR{close_delay}=="50"
    ATTR{closing_wait}=="3000"
    ATTR{io_type}=="0"

  looking at parent device '/devices/platform/serial8250':
    KERNELS=="serial8250"
    SUBSYSTEMS=="platform"
    DRIVERS=="serial8250"

  looking at parent device '/devices/platform':
    KERNELS=="platform"
    SUBSYSTEMS==""
    DRIVERS==""

# Connect USB to the system and Monitor the Uevent
# remove the USB from the System
root@m:~# udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent


Example:
-------
# Connect the USB device.
root@m:~# udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[80864.173700] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2 (usb)
KERNEL[80864.176371] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0 (usb)
KERNEL[80864.176637] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8 (scsi)
KERNEL[80864.176954] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/scsi_host/host8 (scsi_host)
UDEV  [80864.179558] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2 (usb)
UDEV  [80864.185429] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0 (usb)
UDEV  [80864.186228] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8 (scsi)
UDEV  [80864.187256] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/scsi_host/host8 (scsi_host)
KERNEL[80865.183894] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0 (scsi)
KERNEL[80865.183920] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0 (scsi)
UDEV  [80865.185043] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0 (scsi)
UDEV  [80865.186744] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0 (scsi)
KERNEL[80865.209430] add      /devices/virtual/bdi/11:1 (bdi)
KERNEL[80865.209663] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
KERNEL[80865.209982] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_device/8:0:0:0 (scsi_device)
UDEV  [80865.210161] add      /devices/virtual/bdi/11:1 (bdi)
UDEV  [80865.211365] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_device/8:0:0:0 (scsi_device)
KERNEL[80865.211855] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_generic/sg3 (scsi_generic)
KERNEL[80865.212244] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/bsg/8:0:0:0 (bsg)
UDEV  [80865.213882] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_generic/sg3 (scsi_generic)
UDEV  [80865.215214] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/bsg/8:0:0:0 (bsg)
KERNEL[80865.216289] change   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
UDEV  [80865.300548] add      /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
UDEV  [80865.366209] change   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
--------------------------------
# Remove the USB Device
KERNEL[80880.634465] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/bsg/8:0:0:0 (bsg)
KERNEL[80880.634629] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_generic/sg3 (scsi_generic)
KERNEL[80880.634655] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/scsi_device/8:0:0:0 (scsi_device)
KERNEL[80880.634790] remove   /devices/virtual/bdi/11:1 (bdi)
KERNEL[80880.634881] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
KERNEL[80880.635073] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0 (scsi)
KERNEL[80880.635098] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0 (scsi)
KERNEL[80880.635116] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/scsi_host/host8 (scsi_host)
2:1.0/host8/target8:0:0/8:0:0:0/block/sr1 (block)
UDEV  [80880.651967] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0/8:0:0:0 (scsi)
UDEV  [80880.653369] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8/target8:0:0 (scsi)
UDEV  [80880.654570] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host8 (scsi)
UDEV  [80880.655604] remove   /devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0 (usb)

udevadm trigger
----------------
root@m:~#  udevadm trigger --verbose --dry-run --type=devices --subsystem-match=scsi_host

/sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/scsi_host/host0
/sys/devices/pci0000:00/0000:00:1f.2/ata2/host1/scsi_host/host1
/sys/devices/pci0000:00/0000:00:1f.2/ata3/host2/scsi_host/host2
/sys/devices/pci0000:00/0000:00:1f.2/ata4/host3/scsi_host/host3
/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/scsi_host/host4
/sys/devices/pci0000:00/0000:00:1f.2/ata6/host5/scsi_host/host5

Example:
------------
# We can also write the udev rules in /etc/udev/rules.d/* directory and reload the rules dynamically with out any reboot of the system.

Step 1:  root@m:/etc/udev/rules.d# vi 99-yourOwn.rules

Step 2:  Rule can be any thing, Add a device, run a script etc.
           e.g: SUBSYSTEMS=="usb",ATTRS{idVendor}=="0ebc",RUN+="/etc/udev/myscript.sh"

Step 3:  udevadm control --reload-rules
             Reload the rules with out any reboot.

Step 4: udevadm trigger            
            And then check the result in the log files or any verify your expected functionality.

Sometimes, you can skip the step 3: udevadm control --reload-rules 

udevadm test
-------------
The above command used to the test the devices and check the functionality is working or not.

Example:
------------
Step 1:
root@m:~# lsusb
Bus 002 Device 004: ID 0b95:1780 ASIX Electronics Corp. AX88178
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 002: ID 03f9:0100 KeyTronic Corp. KT-2001 Keyboard

Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

Step 2: From above lsusb , get the device name as:

Bus 003 Device 002: ID 03f9:0100 KeyTronic Corp.

The above line can be in Linux file system as 

/dev/bus/usb/003/002

Step 3:  Use the above path and get the device information using udevadm

udevadm info -a -p $(udevadm info -q path -n /dev/bus/usb/003/002)

root@m:~# udevadm info -a -p $(udevadm info -q path -n /dev/bus/usb/003/002)

 looking at device '/devices/pci0000:00/0000:00:1a.0/usb3/3-1':

    KERNEL=="3-1"

    SUBSYSTEM=="usb"

    DRIVER=="usb"

    ATTR{bDeviceSubClass}=="00"

    ATTR{bDeviceProtocol}=="00"

    ATTR{devpath}=="1"

    ATTR{idVendor}=="03f9"

    ATTR{speed}=="1.5"

    ATTR{bNumInterfaces}==" 1"

    ATTR{bConfigurationValue}=="1"

    ATTR{bMaxPacketSize0}=="8"

    ATTR{busnum}=="3"

    ATTR{devnum}=="2"

    ATTR{configuration}==""

    ATTR{bMaxPower}=="100mA"

    ATTR{manufacturer}=="Key Tronic"

    ATTR{removable}=="unknown"

    ATTR{idProduct}=="0100"

    ATTR{bDeviceClass}=="00"

    ATTR{product}=="Keytronic USB Keyboard"

Step 4:

root@m:~# vi /etc/udev/rules.d/10-local.rules

To give permissions for everyone , then add this rule which is matching vendor Id.

SUBSYSTEMS=="usb", ATTR{idVendor}=="03f9", GROUP="users"

Step 5: Test the rule as :  udevadm test  < path of the device>  

root@m:~# udevadm test /devices/pci0000:00/0000:00:1a.0/usb3/3-1

calling: test

version 204

This program is for debugging only, it does not run any program

specified by a RUN key. It may show incorrect results, because

some values may be different, or not available at a simulation run.

=== trie on-disk ===

tool version:          204

file size:         5759486 bytes

header size             80 bytes

strings            1267110 bytes

nodes              4492296 bytes

load module index

read rules file: /etc/udev/rules.d/10-local.rules

read rules file: /lib/udev/rules.d/40-crda.rules

read rules file: /lib/udev/rules.d/60-keyboard.rules

read rules file: /lib/udev/rules.d/69-xorg-vmmouse.rules

read rules file: /lib/udev/rules.d/69-xserver-xorg-input-wacom.rules

read rules file: /lib/udev/rules.d/77-mm-platform-serial-whitelist.rules

read rules file: /lib/udev/rules.d/90-pulseaudio.rules

read rules file: /lib/udev/rules.d/95-cd-devices.rules

read rules file: /lib/udev/rules.d/95-udev-late.rules

read rules file: /etc/udev/rules.d/99-lexscan.rules

rules contain 196608 bytes tokens (16384 * 12 bytes), 30463 bytes strings

13055 strings (122264 bytes), 10544 de-duplicated (94313 bytes), 2512 trie nodes used

GROUP 100 /etc/udev/rules.d/10-local.rules:10

IMPORT builtin 'usb_id' /lib/udev/rules.d/40-libgphoto2-6.rules:3

IMPORT builtin skip 'usb_id' /lib/udev/rules.d/50-udev-default.rules:9

IMPORT builtin 'hwdb' /lib/udev/rules.d/50-udev-default.rules:9

MODE 0664 /lib/udev/rules.d/50-udev-default.rules:36

handling device node '/dev/bus/usb/003/002', devnum=c189:257, mode=0664, uid=0, gid=100

set permissions /dev/bus/usb/003/002, 020664, uid=0, gid=100

preserve already existing symlink '/dev/char/189:257' to '../bus/usb/003/002'

ACTION=add

BUSNUM=003

DEVNAME=/dev/bus/usb/003/002

DEVNUM=002

DEVPATH=/devices/pci0000:00/0000:00:1a.0/usb3/3-1

DEVTYPE=usb_device

DRIVER=usb

ID_BUS=usb

ID_MODEL=Keytronic_USB_Keyboard

ID_MODEL_ENC=Keytronic\x20USB\x20Keyboard

ID_MODEL_FROM_DATABASE=KT-2001 Keyboard

ID_MODEL_ID=0100

ID_REVISION=0102

ID_SERIAL=Key_Tronic_Keytronic_USB_Keyboard

ID_USB_INTERFACES=:030101:

ID_VENDOR=Key_Tronic

ID_VENDOR_ENC=Key\x20Tronic

ID_VENDOR_FROM_DATABASE=KeyTronic Corp.

ID_VENDOR_ID=03f9

MAJOR=189