Determine how many CPUs in the systems

I came across this sniffy forgotten tools to help determine the CPU information. I guess we are all familiar with top. But if you type "1" after top, you are able to see details in the individual A. Using top

# top

top - 10:11:35 up 95 days, 20:02,  2 users,  load average: 0.51, 0.39, 0.20
Tasks: 326 total,   1 running, 325 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.1%sy,  0.0%ni, 99.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  65951272k total, 65647784k used,   303488k free,   221504k buffers
Swap: 33046520k total,        0k used, 33046520k free, 63608900k cached

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
13469 root      20   0 15172 1436  956 R  2.6  0.0   0:00.72 top
1 root      20   0 19352 1520 1208 S  0.0  0.0   0:01.58 init
2 root      20   0     0    0    0 S  0.0  0.0   0:00.01 kthreadd
..............
..............
1

top - 10:11:58 up 95 days, 20:03,  2 users,  load average: 0.46, 0.38, 0.21
Tasks: 310 total,   1 running, 309 sleeping,   0 stopped,   0 zombie
Cpu0  :  0.0%us,  0.3%sy,  0.0%ni, 99.3%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  :  0.3%us,  0.0%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu4  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu5  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu6  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu7  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu8  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu9  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu10 :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu11 :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
.........

---

B. Using lspcu to take a look at summary

# lscpu

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                12
On-line CPU(s) list:   0-11
Thread(s) per core:    1
Core(s) per socket:    6
CPU socket(s):         2
NUMA node(s):          2
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 45
Stepping:              7
CPU MHz:               2501.000
BogoMIPS:              4999.27
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              15360K
NUMA node0 CPU(s):     0-5
NUMA node1 CPU(s):     6-11

Introduction to Systemd on CentOS 7

A few terms we need to grasp:

1. Daemons are processes that wait or run in the background performing various tasks.
2. To listen for connections, a daemon uses a socket.
3. service often refers to one or more daemons

If you are moving from CentOS 6 to CentOS 7, you may be wondering why the need to move to systemd. Here are the features

1. Parallelization capabilities, which increase the boot speed of a system
2. Automatic service dependency management which can prevent long time-out.
3. A method of tracking related processes together by using Linux control groups
4. On-demand starting of daemons without requiring a separate service

---

Listing unit files with systemctl

1. Query the state of all units

   # systemctl

2. Query the state of selected service

   # systemctl --type=service

3. List full output of the selected service. Useful for detailed check and investigation

   # systemctl status sshd.service -l

4. To check whether the particular is active and enabled to start at boot time

   # systemctl is-active sshd
   # systemctl is-enabled sshd

5. List the active state of all loaded units. --all will include inactive units

   # systemctl list-units --type=service
   # systemctl list-units --type=service --all

6. View the enabled and disabled settings for all units

   # systemctl list-unit-files --type=service
   

7. View only failed services.

   # systemctl --failed --type=service
   

    

---

Controlling System Services a. Status of a Service

# systemctl status sshd.service

b. Disable of a Service

# systemctl disable sshd.service

c. Enable and verify the status of a Service

# systemctl enable sshd.service

# systemctl is-enabled sshd.service

d. Reload configuration file of a running service

# systemctl is-enabled sshd.service