IO performance, free, PS, view network status, Linux under Grab packet

One: Monitoring IO performance

Iostat-x disk usage

The last column indicates that the time taken for the disk is longer than
Iotop disk usage

Two: Free command

From left to right, total size, size used, remaining size
The remainder of the available=free+buffers/cached
Total=userd+free+buffers/cached

Three: PS command

View system process PS aux or ps-elf

PID: ID of the process
STAT: Indicates the status of the process, divided into the following types
D a process that cannot be interrupted (usually IO)
R Running Process
S has interrupted the process, usually, most of it is this state
T a process that has stopped or paused
W indicates that there are not enough memory page allocations
X already dead process (as if never appeared)
Z zombie process, can't kill, fight dead garbage process, generally does not appear
< high-priority processes
N Low-priority processes
L was locked in memory paging
S master Process
I Multithreading Process

• Represents a process that is running in the foreground
  is typically used with a pipe character to view a process or his quantity
  PS aux|grep-c process name
  results in minus 1 for the number of processes because grep itself is a process.

  Four: View network status

  To print information such as network connection status, ports that are open to the system, routing tables, and so on.
  Common commands: NETSTAT-LNP print which ports the current system launches
  
  Netstat-an Print network connection status
  

  Tips:
  Netstat-an |awk '/^tcp/{++sta[$NF]} END {for (key in STA) print key, "\ T", Sta[key]} '
  
  count the number of processes in all States
  focus on the number of established

  V: Linux under Grab pack

  Tcpdump
  Install yum install-y tcpdump
  Catch packet
  tcpdump-nn-i eth0
  
  The third and fourth columns show which ip+ port is connected to which ip+ port, and the following information is information about the packet
  - I followed the device name
  -nn to let the third and fourth columns appear as IP and port form, not plus display as host name + service name
  
  -c Specifies the number of packages
  -W writes the specified file, if not added, is displayed as data flow, not packet
  host specified IP
  Port specified ports
  tcpdump-nn-i eth0 host 192.168.233.130 and Port 22-c 100-w 1.cap
  View 1.cap can be Tcpdump-r 1.cap
  also available To download to Windows with Wireshark view.
  Wireshark
  Install yum install-y wireshark
  Usage tshark-n-t a-r http.request-t fields-e "Frame.time"-E "ip.src" -E "Http.host"-E "Http.request.method"-E "Http.request.uri"
  This is similar to a Web Access log.

IO performance, free, PS, view network status, Linux catch-up package