In my earlier post we had discuss about how to find top CPU consuming in Linux. Now we are going to discuss about how to find number of CPU-Cores in Linux.

Question: How to find number of CPU-Cores in Linux.

• Using Proc filesystem

In order to find number of CPU-Cores in Linux we can take help of proc file system. This proc is an pseudo filesystem which keeps track of run-time environment. To Learn more about Proc file-system follow this link.

In order to get cpu information you need to simply cat “/proc/cpuinfo” file within proc. This gives in depth information about the CPU such as vendor_id, cpu family, model, cpu MHz etc. as below:

[root@ip-172-31-16-14 ~]# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 63
model name      : Intel(R) Xeon(R) CPU E5-2676 v3 @ 2.40GHz
stepping        : 2
microcode       : 0x25
cpu MHz         : 2394.660
cache size      : 30720 KB
physical id     : 0
siblings        : 4
core id         : 0
cpu cores       : 4
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 smep bmi2 erms invpcid xsaveopt
bogomips        : 4789.01
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:
-----OUTPUT TRUNCATED---------------------------

Hence to find number of CPU-Cores in Linux with exact details use below commands:

[root@ip-172-31-16-14 ~]# cat /proc/cpuinfo|grep processor
processor       : 0
processor       : 1
processor       : 2
processor       : 3
[root@ip-172-31-16-14 ~]# cat /proc/cpuinfo|grep processor|wc -l
4

Here in this case we have got 4 CPU’s ,numbers ranging from 0 to 3.

• Using lscpu command

You can also find number of CPU-Cores in Linux using lscpu command.

[root@ip-172-31-16-14 ~]# lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 63
Model name:            Intel(R) Xeon(R) CPU E5-2676 v3 @ 2.40GHz
Stepping:              2
CPU MHz:               2394.660
BogoMIPS:              4789.01
Hypervisor vendor:     Xen
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              30720K
NUMA node0 CPU(s):     0-3

In the above out put it’s clearly mentioned number of CPU’s as 4 against the “CPU(s)” heading.

• Using nproc command

This nproc command helps you find number of CPU-Cores in Linux directly without any grep or calculation as below.

[root@ip-172-31-16-14 ~]# nproc
4
[root@ip-172-31-16-14 ~]#

• Using dmidecode command

dmidecode command also gives information about CPU along with other hardware information such as System Information, Chassis Information. To get exact or find number of CPU-Cores in Linux with dmidecode command you need to grep it with the word CPU as below:

[root@ip-172-31-16-14 ~]# dmidecode |grep -i CPU
        Socket Designation: CPU 1
        Socket Designation: CPU 2
        Socket Designation: CPU 3
        Socket Designation: CPU 4
[root@ip-172-31-16-14 ~]#