Linux-Process Management

Process view

• ps aux
ps is process status , which means process status.
  Parameter information

  • a : all displays the processes used, not only the processes started by the current user
  • u : Output process information in the format of user

  • x : Display the processes under all terminals of the current user
    returned messages

    USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
    root         1  0.0  0.2  44672  3864 ?        Ss   1月15   0:02 /usr/lib/syste
    root         2  0.0  0.0      0     0 ?        S    1月15   0:00 [kthreadd]
    root         4  0.0  0.0      0     0 ?        S<   1月15   0:00 [kworker/0:0H]
    

• USER The user who started the process
• PID Process ID
• %CPU CPU share (%)
• %MEM Memory occupancy rate (%)
• VSZ virtual memory (swap space) occupied by 061e43a098cf09
• RSS occupies the size of the resident memory (physical memory)
• TTY process is running on which terminal, ? unknown or no terminal required

• STAT indicates process status

  • S sleep
  • R run
  • Z Zombie
  • < high priority
  • N low priority
  • s parent process
  • + foreground process
• START Process start time
• TIME process take to execute
• COMMAND The command to start the process

• ps ef
  Parameter information

  • e : Display information about all processes in the system
  • f : full display process information in full format
    Display information
    Basically similar aux

• top
  Display information

  top - 01:25:39 up  5:25,  4 users,  load average: 0.03, 0.06, 0.07
  Tasks: 101 total,   4 running,  97 sleeping,   0 stopped,   0 zombie
  %Cpu(s):  1.3 us,  1.7 sy,  0.0 ni, 97.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
  KiB Mem :  1882012 total,   404536 free,   199104 used,  1278372 buff/cache
  KiB Swap:        0 total,        0 free,        0 used.  1486184 avail Mem 
  
    PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND   
   1056 root      20   0   51136   1112    772 R  0.7  0.1   2:33.37 rshim        
      1 root      20   0   44672   3864   2444 S  0.0  0.2   0:02.64 systemd 

  • The first line, the task queue information, is the same as the result of the uptime

    System Time: 01:25:39

    Running time: up 5:25

    Currently logged in users: 4 users

    Load balancing: load average: 0.03, 0.06, 0.07 The three numbers represent the load of 1 minute, 5 minutes and 15 minutes respectively

  • second line, task

    Tasks: 101 total, 4 running, 97 sleeping, 0 stopped, 0 zombie total processes: 101 running: 4 sleeping: 97 stopped: 0 zombie processes: 0

  • The third line, the cpu share

    %Cpu(s): 1.3 us, 1.7 sy, 0.0 ni, 97.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st

    • us - user space: 1.3%
    • sy - Kernel space (sysctl): 1.7%
    • ni - Processes whose priority has changed (nice): 0.0%
    • id - idle cpu (idol): 97.0%
    • wa - io wait (wait): 0.0%
    • hi - Hard interrupt usage (Hardware IRQ): 0.0%
    • si - Software Interrupts: 0.0%

  • The fourth line, the memory status

    KiB Mem : 1882012 total, 404536 free, 199104 used, 1278372 buff/cache total memory = free memory + used memory + cached memory

  • The fifth line, swap swap partition information

    KiB Swap: 0 total, 0 free, 0 used. 1486184 avail Mem

    linux order to improve the efficiency and speed of reading and writing, the file will be cached in memory, this is part of the cache memory cache memory , even after the end of your program to run this memory will not be released, which leads to your linux system After the program reads and writes files frequently, the available physical memory becomes less. When the physical memory becomes insufficient, it needs to release some space from the physical memory. This part of the released space information will be temporarily reserved in the swap space. Wait until the program When this part of data is needed for operation Swap partition to the memory, so when the Swap used changes frequently, it means that the physical memory of the system is not enough at this time.

    • The sixth line, the meaning of the field is basically similar ps aux
top -p process pid can only see the process information pid

  process control

  Process priority control

  nice -n 10 XXX : nice xxx process is started to set its priority to 10. The range of this value is (-20~19), the smaller the value, the higher the priority.
renice -n -20 17265 : The pid = 17265 priority of a process of re-setting -20

  Process job control

  ./xxx.sh & The process to be started, running in the background.
jobs can view the processes running in the background.

  [2]+ Running nice -n 10 ./minio server /data/minio.data/ &

  fg 2 : fg + jobs number brings the process to the foreground.
ctrl + z : Change the process to stopped state.
bg 2 : bg + jobs number Run this program in the background.

  Service Management Tools

  service and systemctl are Linux manages services.

• service actually goes to the /etc/init.d directory to execute related programs

  service redis start
  等同于
  /etc/init.d/redis start
  

  service xxx start Start service

  service xxx stop shutdown service

  service xxx restart restart service

  service xxx status View service status

• systemctl is Linux latest initialize the system init , the role is to improve the system's boot speed, systemctl also compatible service command that systemctl also to init.d directory continue implementation of relevant procedures.

  systemctl start xxx Start the service

  systemctl stop xxx shutdown service

  systemctl restart xxx restart service

  systemctl status xxx View service status

  systemctl reload xxx reload service

  systemctl enable xxx boot service

  systemctl disable xxx Start and stop service