Monitoring Processes

1. 程序(process)：在系統中觸發任何一個事件時，都會將其定義為一個程序並給一個 ID，即 PID(Process ID)。
2. 某一程式佔用太多的系統資源，造成系統變得很慢時，能否找出最耗系統的程序，刪除該程序讓系統恢復正常？
3. ps觀查程序
   

   [root@deyu ~]# ps
     PID TTY          TIME CMD
    2960 pts/1    00:00:00 su
    3019 pts/1    00:00:00 bash
    6522 pts/1    00:00:00 ps
   
   [root@deyu ~]# ps --help
   ********* simple selection *********  ***
   ....
   a  all w/ tty, including other users ... 
   x  processes w/o controlling ttys    ... 
   -l,l long          u  user-oriented  ...
   ........
   
   [root@deyu ~]# ps aux
   USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
   root         1  0.0  0.0  21336  1436 ?        Ss   06:41   0:00 /sbin/init
   root         2  0.0  0.0      0     0 ?        S    06:41   0:00 [kthreadd]
   root         3  0.0  0.0      0     0 ?        S    06:41   0:00 [migration/0]
   .......
   

4. top觀察程序
   

   [root@deyu ~]# top
   
   top - 15:56:47 up  9:15,  9 users,  load average: 0.00, 0.00, 0.00
   Tasks: 210 total,   2 running, 208 sleeping,   0 stopped,   0 zombie
   Cpu(s):  2.0%us,  1.3%sy,  0.0%ni, 96.6%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
   Mem:   3021464k total,  1239316k used,  1782148k free,   101984k buffers
   Swap:   253936k total,        0k used,   253936k free,   458520k cached
   
     PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                         
    2664 dywang    20   0  309m  18m  12m S  3.2  0.6   0:16.62 gnome-terminal                                                  
    2419 root      20   0  175m  33m  12m S  2.9  1.1   3:30.19 Xorg                                                            
    3191 dywang    20   0  938m 196m  38m S  0.5  6.6   9:58.24 firefox
   
   ## h key provides more information
   ## M key orders processes by memory use
   ## P key orders processes by CPU use
   ## q key quit top