Basic O & M knowledge free-M, uptime, top, show processlist

1. Show processlist view the number of processes in MySQL

2. freem-M view memory

3. view system running status on top

4. View load in uptime

 

Use crontab-L to set the threshold, and then send an email alarm.

The Linux uptime command is used to obtain the host running time and query the Linux system load. In the past, the uptime command only showed how long the system was running. Now, we can display how long the system has been running. The information is displayed in sequence as follows: current time, how long the system has been running, how many login users are there, and the average load of the system in the past 1 minute, 5 minutes, and 15 minutes.

51cto editing recommendations: Linux monitoring tools

The uptime command is easy to use: directly enter

# Uptime

You can.

Input example:

18:02:41 up 41 days, 1 user, load average: 0.00, 0.00, 0.00

1 can be considered as the optimal load value. The load changes with the system. Single CPU Systems 1-3 and SMP systems 6-10 are acceptable.

Another parameter-V is used to query the version. (Note the uppercase letter V)

[Linux @ localhost] $ uptime-V

Procps version 3.2.7

[Linux @ localhost] $ uptime

The result is as follows:

10:19:04 up 257 days, 12 users, load average: 2.10, 2.10, 2.09

Description:

10:19:04 // current system time

Up 257 days, // the host has run time. The larger the time, the more stable your machine is.

12 User // number of user connections, which is the total number of connections rather than the number of users

Load average // average system load, which counts the average system load for the last 1, 5, and 15 minutes

So what is the average system load? The average system load refers to the average number of processes in the queue running at a specific time interval.

If the number of active processes per CPU core is not greater than 3, the system performance is good. If the number of tasks in each CPU kernel is greater than 5, the performance of this machine is seriously affected.

If your Linux host is a dual-core CPU, when the load average is 6, it indicates that the host has been fully used.

How long has it taken to start online CPU average load for several users (3 in total)
First: average load within 1 minute
Second: average load in 5 minutes
Third: average load within 15 minutes

When the system load is too large, multiple commands are blocked in memory and I/O systems.
In a large Linux system, 2 and 3 indicate light loads, 5 and 6 indicate moderate loads, and 10 or more indicate overload.