10.6 Monitor io performance
iostat -x : Monitor disk usage (note the column of %util yum install -y sysstat)
iostat -x 1 : Monitor the usage of disk, update once per second (note the column of %util yum install -y sysstat)
iotop dynamic healthy disk usage (yum install -y iotop (similar to the top command))
%util: percentage of working time or busy time to total time
rrqm/s: number of merged read operations per second
wrqm/s : number of combined write operations per second
r/s : number of read operations per second
w/s : number of write operations per second
rMB/s : number of MB bytes read per second
wMB/s: number of writes per second MB bytes
avgrq-sz: The average number of sectors per IO, that is, the average size of all requests, in sectors (512 bytes)
avgqu-sz: The average is the number of completed IO requests, that is, the average meaning mountain The request queue length
await: the average time required for each IO, including the waiting time in the queue, and the effective time for the disk controller to process this request. 
10.7 free command: View the current total system memory size and memory usage
10.8 ps command: You can view the process of the system 
10.9 netstat View the network status
netstat: This command can print out the connection status of the network, the open ports of the system, and the relevant information of the routing table. 
Remember this command:
netstat -an|awk '/^tcp/{++sta[$NF]}END {for(key in sta)print key,"\t",sta[key]}'
10.10 Packet capture under linux