two. Static ps command to view process statistics
1. ps aux command
2 ps -elf
ps aux --no-header | more to remove the head
Output content analysis
[top] current system time
[1:54 system has been running one hour 54 minutes]
2 users currently logged in [2] Users
load average: 0.00, 0.00, 0.00 [system load average: 1 minute, 5 five minutes, 15 minutes]
Tasks: 108 total [tasks: 108 total process]
1 running [a] process is running
107 sleepping process to sleep [107]
0 stoppd process stops [0]
[0 0 zombie zombie process (freezing process)]
Cpu (s): 0.0% us user control of CPU [percentage]
0.0% sy [kernel space occupied by the percentage of CPU]
0.0% ni [priority processes within the user process control changed occupancy percentage of CPU]
100.0% [percentage] idle CUP
MEN: 1012352K total [total physical memory 1012352K]
3424k used [used] these physical memory
352k free [free up]
Four view process information
1 pgrep # PID query information based on specific criteria
-l # displayed process name
-U # specify a specific user
-t # designated terminal
2 pstree -aup
Five process was started
Hand 1 Start
(1) Reception Start
(2) Background start: end of line command added ampersand
If you do not want to call this program nohup rearmost front Add Add &
(3) jobs to view a list of background tasks simultaneously -l displays the PID number
fell into the background foreground fg #
bg # pause the background processes running in the background adjusted
Run (4) to terminate the process
kill # terminates the specified process PID number
killall # terminate all processes with the specified name
No. 9 termination option forces
<3 pkill # terminates the corresponding process depending on the particular conditions
2 scheduled start
(1) at the command # Set time schedule (and some not at CentOS yum command need to install or rpm)
Basic Operations
Ctrl + D to save and exit
atq # query existing time schedule
atrm # delete the first few tasks
(2) periodic task set command crontab
Edit: crontab -e -u [user name]
View: crontab -l [-u username]
Empty: crontab -r [-u username]
Note -u option is only available to the user root
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In fact, the role is a shell command interpreter
Under five absolute path echo $ PATH # View commands used where
date of usage
watch -n 3 'date' # display dynamic execution time of 3 seconds
date -s "year - month - day hour: minutes: seconds" # can modify the current time
Time synchronization ntpdate pool.ntp.org #
Path 5: / usr / sbin / / usr / local / sbin / usr / bin / / usr / local / bin / root / bin
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crontab task configuration format
"Points - when - Day - Month - Week" command +
Min: 0-59
When: 0-23
12:00
Day: 1-31
Month: 1-12
Week: 1-7