1: Process management
Process view
ps aux #View all processes in the system. BSD operating system format
a foreground process
x background process
u shows which user the process was created by
ps -le #View all processes in the system. Linux standard format
-l display more detailed information
-e show all information
top #View the health status of the command
The first five lines of the top command are explained in the following pictures
top command option 
pstree to view the process tree
Syntax: pstree [options]
Options:
-p: show the PID of the process
-u: show the user of the process
kill process
kill command
kill -l to view available process signals
eg：
kill -1 88888 restart process number is 88888 process
kill -9 88888 Force close the process ID is 88888
kill -15 88888 normally close the process number is 88888 process
killall command
kill process by process name
Syntax: killall [options] [signals] process name
Options:
-i: interactive, ask if you want to kill a process
-I: ignore case of process names
eg: killall -9 mongo forcibly kills the process whose process name is mongo
pkill command
kill process by process name
Syntax: pkill [options] [signals] process name
Options:
-t terminal number: kick out the user according to the terminal number (used in conjunction with the w command)
eg: pkill -9 mongo forcibly kills the process whose process name is mongo
eg: pkill -9 -t tty1 forcibly kills the process logged in from the tty1 terminal
View a specified service in a tree view
pstree -p | grep mongo
Two: work management
put the process in the background
Method 1: Command &
Method 2: Press the ctrl+z shortcut key during the execution of the command
Note: The difference between Fa 1 and Fa Er is that Fa 1 will continue to run in the background, while Fa 2 will be suspended in the background.
See what's going on in the background
jobs command
Syntax: jobs [options]
Options:
-l show the pid of the job
Note: The "+" sign represents the last job that was put into the background, and it is also the job that is restored by default when the job is resumed.
"-" represents the second-to-last job put into the background
Foreground execution that resumes work suspended in the background
fg command
fg % job number
parameter:
% job number: The % sign can be omitted, but pay attention to the difference between job number and PID.
Resume the work suspended in the background and execute it in the background
bg command
bg % job number
Three: check system resources
vmstat command
View monitoring system resources
Syntax: vmstat [refresh delay refresh times]
eg: vmstat 1 3 Monitor system resources three times with one second interval each time.
dmesg command
Display kernel self-test information at boot time
Syntax: dmesg
eg：dmesg | grep CPU
free command
Check the memory usage status
Syntax: free[options]
Options:
-b in bytes
-k KB in units
-m MB in units
-g GB in units
eg: free -g View memory usage in GB.
View CPU information
cat /proc/cpuinfo
uptime command
Viewing the system running time is equivalent to the first line of the top command. The w command can also see the same content.
View system and kernel related information
uname command
View system kernel version information command
Syntax: uname [options]
Options:
-a View all relevant information of the system;
-r View kernel version;
-s View the kernel name;
Determine the current number of digits in the current system
file /bin/ls
Query the current release version of the Linux system
lsb_release -a
lsof command
List process open or use file information
Syntax: lsof [options]
Options:
-c string: List only files opened by processes starting with the string
-u username: only list files opened by a user's process
-p PID: List files opened by a PID process
eg: lsof -c init # List processes related to init
Four: Scheduled task management
Function: a, backup
b, shut down
c, restart, etc.
crond service (to ensure that the service is started, the scheduled task will take effect)
Check if crond is started: ps aux | grep crond
service crond start prompts "crond: unrecognized service" indicating that it is not installed
Install: yum install vixie-cron
Start crond on boot: ? ?
crontab command
Syntax: crontab [options]
Options:
-e: Edit crontab timing user
-l: Query crontab tasks
-r: delete all crontab tasks of the current user
Five parameters of timed tasks
Special symbols for timed tasks
Timed task demo
eg：
* * * * * echo $(date) >> /temp/dingshi.log Write the current system time to the dingshi.log file every minute
30 18 * * 6 halt #Timely shutdown at 18:30 every Saturday.
30 18 * * 6 /sbin/shutdown -h now #Restart regularly at 18:30 every Saturday.
# Note: -h parameter is shutdown -r parameter is restart.
If shutdown: command not found error, use whereis shutdown to find the path. Reference article: http://www.jb51.net/article/15008.htm