How do you find out the number of CPU cores available in your Linux system? Here are a number of way, pick the one which works for you -

1. nproc command -

[daniel@kauai tmp]$ nproc
2

2. /proc/cpuinfo

[daniel@kauai tmp]$ grep proc /proc/cpuinfo 
processor	: 0
processor	: 1

3. top - run top command and press ‘1’ (number 1), you will see the list of cores at the top, right below tasks.

Cpu0  :  0.7%us,  0.3%sy,  0.0%ni, 99.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu1  :  2.7%us,  1.0%sy,  0.0%ni, 96.3%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st

4. lscpu - display information about the CPU architecture. Count Sockets times Core(s) per socket, in this case 2 x 1=2 -

[daniel@kauai tmp]$ 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:             AuthenticAMD
CPU family:            16
Model:                 6
Model name:            AMD Athlon(tm) II X2 250 Processor
Stepping:              3
CPU MHz:               3000.000
BogoMIPS:              6027.19
Virtualization:        AMD-V
L1d cache:             64K
L1i cache:             64K
L2 cache:              1024K
NUMA node0 CPU(s):     0,1

5. Kernel threads - pick one of the kernel house keeping threads, such as “migration” or “watchdog” and see on how many cores it is running -

[daniel@kauai tmp]$ ps aux |grep '[m]igration'
root         3  0.0  0.0      0     0 ?        S    Dec09   0:02 [migration/0]
root         7  0.0  0.0      0     0 ?        S    Dec09   0:02 [migration/1]

[daniel@kauai tmp]$ ps aux |grep '[w]atchdog'
root         6  0.0  0.0      0     0 ?        S    Dec09   0:00 [watchdog/0]
root        10  0.0  0.0      0     0 ?        S    Dec09   0:00 [watchdog/1]
FILED UNDERcpu