How to Find Number of CPU Cores in linux ?

You can use the lscpu or nproc command to display the number of processing units available to the current process, which may be less than the number of online processors (please note that not all server supports hotplug a CPU on a running Linux system).

The proc file system is a pseudo-file system which is used as an interface to kernel data structures. It is commonly mounted at /proc. The /proc/cpuinfo file is nothing but a collection of CPU and system architecture dependent items, for each supported architecture a different list. Two common entries are processor which gives CPU number and bogomips; a system constant that is calculated during kernel initialization.

Method 1:

Using nproc

 nproc

Example:

linux@linuxforfreshers.com:~$ nproc

2

Method 2:

lscpu gathers CPU architecture information form /proc/cpuinfon in human-read-able format:

Using lscpu

Example:

linux@linuxforfreshers.com:~$ lscpu

Architecture:          x86_64

CPU op-mode(s):        32-bit, 64-bit

Byte Order:            Little Endian

CPU(s):                2

On-line CPU(s) list:   0,1

Thread(s) per core:    1

Core(s) per socket:    2

Socket(s):             1

NUMA node(s):          1

Vendor ID:             GenuineIntel

CPU family:            6

Model:                 15

Stepping:              2

CPU MHz:               1596.000

BogoMIPS:              4255.98

Virtualization:        VT-x

L1d cache:             32K

L1i cache:             32K

L2 cache:              2048K

NUMA node0 CPU(s):     0,1

Method 3:

Using /proc/cpuinfo

The /proc/cpuinfo and sysfs stores info about your CPU architecture ike number of CPUs, threads, cores, sockets, NUMA nodes, information about CPU caches, CPU family, model, bogoMIPS, yte order and much more:

Example 1: less /proc/cpuinfo

Or

Example 2:

linux@linuxforfreshers.com:~$ cat /proc/cpuinfo | grep -i 'core id'

core id             : 0

core id             : 1

Example 3:

linux@linuxforfreshers.com:~$ lscpu | egrep 'Thread|Core|Socket'

Thread(s) per core:    1

Core(s) per socket:    2

Socket(s):             1

Method 4:

Using dmidecode

Example :

linux@linuxforfreshers.com:~$ sudo dmidecode -t 4 | egrep 'Core Count'

            Core Count: 2