Notes common Linux commands (ii) processes and ports

View system processes

• ps: the current process for reporting system status
  • a: the display program execution in all of the terminal

ps -ef/ps aux： 这两个命令都是查看当前系统正在运行进程，两者的区别是展示格式不同。
如果想要查看特定的进程可以使用这样的格式：ps aux|grep redis （查看包括redis字符串的进程）

[root@VM_0_4_centos ~]# ps -ef | grep nginx
root      1892     1  0 15:19 ?        00:00:00 nginx: master process nginx
nginx     1893  1892  0 15:19 ?        00:00:00 nginx: worker process
root      1908  1248  0 15:19 pts/0    00:00:00 grep --color=auto nginx



root@iZuf6c0rnhno78oq2pxylnZ:~# ps -aux 
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND

USER 进程的属主；
PID 进程的ID；
PPID 父进程；
%CPU 进程占用的CPU百分比；
%MEM 占用内存的百分比；
NI 进程的NICE值，数值大，表示较少占用CPU时间；
VSZ 进程虚拟大小；
RSS 驻留中页的数量；
TTY 终端ID
STAT 进程状态（有以下几种）
D 无法中断的休眠状态（通常 IO 的进程）；
R 正在运行可中在队列中可过行的；
S 处于休眠状态；
T 停止或被追踪；
W 进入内存交换（从内核2.6开始无效）；
X 死掉的进程（从来没见过）；
Z 僵尸进程；

Kill the process

• kill: to delete the program or work execution
  • Syntax: kill (Option) (parameters)
  • Options:
    • a: When dealing with the current process, does not limit the correspondence between the command name and the process ID;
      
    • l <message number>: If left <message number> option, the -l option will list the names of all of the information;
    • p: Specifies the kill command to print only the process ID related processes, without sending any signal;
    • s <message name or number>: Specifies the information sent;
    • u: Specifies the user
  • Parameters: process or job ID: Specifies the process or job to be deleted. Common PID
• List all signal names
  • kill -l

  root@iZuf6c0rnhno78oq2pxylnZ:~# kill -l
   1) SIGHUP       2) SIGINT       3) SIGQUIT      4) SIGILL       5) SIGTRAP
   6) SIGABRT      7) SIGBUS       8) SIGFPE       9) SIGKILL     10) SIGUSR1
  ·
  ·
  ·

• Numerical designation signal obtained
  • kill -l KILL

  root@iZuf6c0rnhno78oq2pxylnZ:~# kill -l KILL
  9

• Kill the process

1. View nginx processes: ps -aux | grep nginx

root@iZuf6c0rnhno78oq2pxylnZ:~# ps -aux | grep nginx
root       323  0.0  0.2 117656  4924 ?        Ss    2019   0:00 nginx: master process nginx
root      3412  0.0  0.0  14224   968 pts/0    S+   16:32   0:00 grep --color=auto nginx
www-data 30902  0.0  0.2 118032  4992 ?        S    Jan04   0:00 nginx: worker process

2, killing nginx processes: kill -9 323 30902

root@iZuf6c0rnhno78oq2pxylnZ:~# kill -9 323 30902

Viewer occupied port number

ps: lsof -i requires root permissions to perform

• lsof: the current system is a tool list of open files
  • Syntax: lsof (option)
  • Options
    • a: list the process of opening an existing file;
    • c <process name>: lists the specified process open files;
    • g: GID list number of the process details;
    • d <file number>: Lists the occupation process the file number;
    • d <directory>: List directory files from being opened;
    • D <directory>: recursively list directory files from being opened;
    • n <directory>: List of files using NFS;
    • i <condition>: Lists qualifying process. (4,6, agreement: port, @ip)
    • p <process ID>: List the process is specified as open files;
    • u: UID number listed details of the process;
    • h: display help information;
    • v: Displays version information.
• Check occupied port 80 program
• lsof -i: port number

root@iZuf6c0rnhno78oq2pxylnZ:~# lsof -i:80
COMMAND     PID     USER   FD   TYPE   DEVICE SIZE/OFF NODE NAME
AliYunDun   822     root   21u  IPv4 46829108      0t0  TCP 172.17.1.142:37126->100.100.30.25:http (ESTABLISHED)
nginx     19170     root    6u  IPv4 69865848      0t0  TCP 172.17.1.142:http (LISTEN)
nginx     19173 www-data    6u  IPv4 69865848      0t0  TCP 172.17.1.142:http (LISTEN)

• Check occupied by the process according to the port number PID
• lsof -i | grep pid

root@iZuf6c0rnhno78oq2pxylnZ:~# lsof -i | grep 19170
nginx     19170            root    6u  IPv4 69865848      0t0  TCP 172.17.1.142:http (LISTEN)
nginx     19170            root    7u  IPv4 69865849      0t0  TCP 172.17.1.142:81 (LISTEN)
nginx     19170            root    8u  IPv4 69865850      0t0  TCP 172.17.1.142:8000 (LISTEN)
nginx     19170            root    9u  IPv4 69865851      0t0  TCP 172.17.1.142:8001 (LISTEN)
nginx     19170            root   10u  IPv4 69865852      0t0  TCP 172.17.1.142:8002 (LISTEN)

• According to the process name to view the port number occupied

root@iZuf6c0rnhno78oq2pxylnZ:~# lsof -i | grep nginx
nginx     19170            root    6u  IPv4 69865848      0t0  TCP 172.17.1.142:http (LISTEN)
nginx     19170            root    7u  IPv4 69865849      0t0  TCP 172.17.1.142:81 (LISTEN)
nginx     19170            root    8u  IPv4 69865850      0t0  TCP 172.17.1.142:8000 (LISTEN)
nginx     19170            root    9u  IPv4 69865851      0t0  TCP 172.17.1.142:8001 (LISTEN)
nginx     19170            root   10u  IPv4 69865852      0t0  TCP 172.17.1.142:8002 (LISTEN)
nginx     19173        www-data    6u  IPv4 69865848      0t0  TCP 172.17.1.142:http (LISTEN)
nginx     19173        www-data    7u  IPv4 69865849      0t0  TCP 172.17.1.142:81 (LISTEN)
nginx     19173        www-data    8u  IPv4 69865850      0t0  TCP 172.17.1.142:8000 (LISTEN)
nginx     19173        www-data    9u  IPv4 69865851      0t0  TCP 172.17.1.142:8001 (LISTEN)
nginx     19173        www-data   10u  IPv4 69865852      0t0  TCP 172.17.1.142:8002 (LISTEN)

View Linux network system status information

• netstat
  • Syntax: netstat (option)
  • Options:
    • or a --all: all wiring in the Socket;
    • n or --numeric: ip address directly, without passing through the domain name server;
    • p or --programs: display program identifier and the program name being used Socket;
• According to the process name to view the port number occupied

root@iZuf6c0rnhno78oq2pxylnZ:~# netstat -anp | grep nginx
tcp        0      0 172.17.1.142:8000       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:8001       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:8002       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:80         0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:81         0.0.0.0:*               LISTEN      19170/nginx: master
unix  3      [ ]         STREAM     CONNECTED     69865863 19170/nginx: master 
unix  3      [ ]         STREAM     CONNECTED     69865862 19170/nginx: master 

• Check occupied by the process according to the port number PID

root@iZuf6c0rnhno78oq2pxylnZ:~# netstat -anp | grep 80
tcp        0      0 172.17.1.142:8000       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:8001       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:8002       0.0.0.0:*               LISTEN      19170/nginx: master
tcp        0      0 172.17.1.142:80         0.0.0.0:*               LISTEN      19170/nginx: master

Reference article

Every day a linux command (42): kill command
Linux view the port occupancy
Linux command Daquan
how to view the process of occupation in Linux port number