Linux System Management Preliminary (ii) IO, free, PS, netstat command editing

10.6 Monitoring IO Performance
10.7 Free Command
10.8 PS Command
10.9 Viewing network status
10.10 Linux under Grab Bag

First, Iostat and Iotop command

Iostat command and Iotop, command to see the system disk work, timely discovery of disk problems, these two tools are not the system comes with, the need for Yum installation
Where the Iostat command is in the same (SYSSTAT) package as the SAR command mentioned in the previous blog, you can use the Iostat command if you can use the SAR command.
Installation commands

Yum Install Epel Installing the Epel extension source first
Yum Install Sysstat Iotop

(a) Iostat command, see util if the value is too high, the disk is busy or there is a problem.

To view disk usage

Iostat-x

Pay attention to the value of the red, the system is explained below, anyway this value is very high the system reacts very slowly, either to change the hard disk, or to find out what caused the disk usage to soar.
%util Percentage of elapsed time during which I/O requests were issued to the device (bandwidth utilization for the device ). Device saturation occurs when the this value was close to 100%.

(b) Iotop, production see which process takes up more processes

On the specific server to see more clearly, disk read and write the most in the first row.

II. FREE command

To see how much memory is being used
Free-m free-h
Buff
Cache

III. PS Command View system process

Ps-aux

A zombie process scenario with Nigix enabled and the child process may enter the zombie process when the parent process is accidentally killed

Iv. netstat command

Netstat is used to view network status,
TCP Three-time handshake
Wave four times
NETSTAT-LNP Viewing the Listening port
Netstat-an Viewing the network connection status of the system
Ss-an View Network Connection Status
Little Tricks
Netstat-an|awk '/^txp

Five, packaging tools

You will need to grab the packet when the network is out of the ordinary
When the network has abnormal traffic, you need to catch the packet to see
such as seeing attacks, frequently accessing some ports some requests

Tcpdump
Usage Txpdump-nn

Wireshark

Linux System Management Preliminary (ii) IO, free, PS, netstat command editing