Linux Display CPU Information Number of CPUs and Their Speed

How do I display CPU information like number of CPUs, threads, cores, sockets, NUMA nodes, information about CPU caches, CPU family, model and stepping and their speed on Linux operating systems?

You need to use Proc (/proc) file system provides information about CPU and their speed which is a pseudo-filesystem. It is used as an interface to kernel data structures. It is commonly mounted at /proc. Most of it is read-only, but some files allow kernel variables to be changed.

You can also use the command called lscpu to display information on CPU architecture on modern Linux distributions.

Display the number of processors in Linux

You need to use the /proc/cpuinfo file. This is 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. SMP machines have information for each CPU. Type the following command:
$ more /proc/cpuinfo
OR
$ cat /proc/cpuinfo
OR
$ less /proc/cpuinfo
Sample outputs:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.00GHz
stepping        : 3
cpu MHz         : 2992.991
cache size      : 2048 KB
physical id     : 0
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2
ss ht tm pbe nx lm pni monitor ds_cpl cid
bogomips        : 5931.00
processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.00GHz
stepping        : 3
cpu MHz         : 2992.991
cache size      : 2048 KB
physical id     : 0
siblings        : 2
.....
...
....

You can narrow down the output with the following commands, to display number of processors in the system:
$ grep processor /proc/cpuinfo

Say hello to lscpu

The lscpu command is CPU architecture information helper and can be found under Fedora Linux / RHEL / CentOS v6+ / Debian Linux v6+ and many other latest distro includes this command.
$ lscpu
Sample outputs:

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
CPU(s):                8
Thread(s) per core:    2
Core(s) per socket:    4
CPU socket(s):         1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 30
Stepping:              5
CPU MHz:               1199.000
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              8192K

Warning : lscput command has bug and sometimes in Xen Dom0 kernel reports wrong data. So please use /proc/cpuinfo for verification purpose.