Process in Linux: an executable running instance that has been started
1, PID: process ID (each new process has a unique PID)
< p>2, PPID: the ID of the parent process
3, any process can create a child process
4, above redhat 7, the parent process of all processes: systemd< /p>
In redhat 5 and 6, the parent process of all processes: init
ps displays the status of the current process pair (the parameters of ps are very many, view it by man)
Common options:
-aux: List all processes
-ef: List all processes
-l: List processes related to the current user
-u user: view the process status of a user
top: You can view the real-time process status
The meaning of some letters in the above ps:
< p > Running:
R: the process is running or waiting to run
sleeping:
S: sleeping but can be awakened
D: Sleeping and cannot be awakened. The process is interrupted, which may cause an abnormal state of the device.
K: Sleeping and cannot be awakened, the process can be interrupted.
has been stopped:
T: The process is stopped, but it can be restored by other processes
T: the process being debugged
zombie stop:
Z: the child process sends a signal to the parent process when it exits, all resources except PID are released
X: the parent process has acquired the structure of the child process, The child process can be completely released, and you can’t see it in the state process
In ps -aux
Process priority:
1,< high priority Level
2, n low priority
3, s contains child processes
4, + process group in the background
ps -aux parameter explanation
1, %CPU: occupied CPU usage rate
2, %MEM: occupied memory usage rate
3, VSZ: Occupied virtual memory size
4, RSS: Occupied memory size
5, TTY: the minor device number of the terminal (minor device number of tty)
6, STAT: the status of the itinerary
7, START: the time the process started
8, TIME: the execution time
9, COMMAND ：Command executed
Process: an independent program run by Linux itself
Interactive process: a process started by a shell, which can run in the foreground, It can also run in the background
Batch process: it is a sequence of processes and has no connection with the terminal
Monitoring process (daemon): the process started when the Linux system is started, and Running in the background
Job: A process that is being executed, and the job can contain one or more processes.
Job control: Control the behavior of the running process. Such as: suspend a process, wait for a while and then execute it. This allows users to switch between multiple jobs.
&: Use this symbol after any command to allow the command to be executed in the background
jobs: You can view what is in the background Running job (front and back job status)
-l: In addition to listing the job number, PID is also listed
-r: List the jobs that only run in the background
-s: List jobs that are only suspended in the background
sleep: Delay a few seconds
ctrl + c: interrupt
ctrl + z: Hanging
< p>fg: transfer the background command to the foreground to continue execution, and cannot continue to put it back into the background
% job number
bg: continue the execution of the suspended command in the background
% job number
ps -j: display current job process information
TGID: thread group ID number
SID: reply ID number
Linux interrupt process
Signals: operations passed to the Linux process
kill -l displays all the signals that can be passed to the Linux process
Commonly used:
kill -9 PID: kill the iyge process-force
kill -15 PID: terminate a process in a normal way
kill -2: with ctrl+ The operation of c is the same