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Friday, August 5, 2011

Linux Top Command

Linux top Command
                                                            In most Unix-like operating systems, the top command is a system monitor tool that produces a frequently-updated list of processes. By default, the processes are ordered by percentage of CPU usage, with only the "top" CPU consumers shown. top shows how much processing power and memory are being used, as well as other information about the running processes. Some versions of top allow extensive customization of the display, such as choice of columns or sorting method.
                                     top is useful for system administrators, as it shows which users and processes are consuming the most system resources at any given time.
The ps command is similar to top, but instead produces a one-time "snapshot" list of processes

#top 
top - 12:59:35 up  3:25,  8 users,  load average: 0.07, 0.17, 0.24
Tasks: 169 total,   2 running, 166 sleeping,   0 stopped,   1 zombie
Cpu(s):  0.7%us,  1.3%sy,  0.0%ni, 98.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   2037228k total,  1970468k used,    66760k free,     2572k buffers
Swap:  8193108k total,      188k used,  8192920k free,   176744k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2579 root      18   0 1607m 627m 8716 S  1.3 31.6  17:10.36 java
 5732 root      15   0  650m  63m  16m S  1.0  3.2   2:57.50 VirtualBox
    1 root      15   0  2160  628  544 S  0.0  0.0   0:00.21 init
    2 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00 migration/0
    3 root      34  19     0    0    0 S  0.0  0.0   0:00.00 ksoftirqd/0
    4 root      RT  -5     0    0    0 S  0.0  0.0   0:00.00 watchdog/0
    5 root      10  -5     0    0    0 S  0.0  0.0   0:00.01 events/0
    6 root      15  -5     0    0    0 S  0.0  0.0   0:00.00 khelper
    7 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 kthread
   10 root      10  -5     0    0    0 S  0.0  0.0   0:00.05 kblockd/0
   11 root      20  -5     0    0    0 S  0.0  0.0   0:00.00 kacpid
  141 root      20  -5     0    0    0 S  0.0  0.0   0:00.00 cqueue/0
  144 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 khubd
  146 root      12  -5     0    0    0 S  0.0  0.0   0:00.00 kseriod
  207 root      22   0     0    0    0 S  0.0  0.0   0:00.00 khungtaskd
  208 root      15   0     0    0    0 S  0.0  0.0   0:00.06 pdflush
  209 root      15   0     0    0    0 S  0.0  0.0   0:00.03 pdflush
  210 root      10  -5     0    0    0 S  0.0  0.0   0:00.64 kswapd0
  211 root      20  -5     0    0    0 S  0.0  0.0   0:00.00 aio/0
  368 root      11  -5     0    0    0 S  0.0  0.0   0:00.00 kpsmoused
  391 root      10  -5     0    0    0 S  0.0  0.0   0:00.42 ata/0
  392 root      16  -5     0    0    0 S  0.0  0.0   0:00.00 ata_aux
  395 root      13  -5     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_0
  396 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_1
  397 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_2
  398 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_3
  401 root      10  -5     0    0    0 S  0.0  0.0   0:00.49 scsi_eh_4
  402 root      11  -5     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_5
  405 root      12  -5     0    0    0 S  0.0  0.0   0:00.00 kstriped
  414 root      16  -5     0    0    0 S  0.0  0.0   0:00.00 ksnapd
  423 root      10  -5     0    0    0 S  0.0  0.0   0:00.26 kjournald
  449 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 kauditd
  486 root      16  -4  2568  940  392 S  0.0  0.0   0:00.23 udevd
 1420 root      15  -5     0    0    0 S  0.0  0.0   0:00.00 hd-audio0
 1953 root      20  -5     0    0    0 S  0.0  0.0   0:00.00 kmpathd/0
 
top command options:

Line1: Gives System present time, up time of the machine, number of users logged in, Load average on system at 5, 10, 15 min interval.
Line2: Gives total number of process on the machine, number of running process, number of sleeping process, number of stopped process, number of Zambie process.
Line3: Gives you CPU details
Line4 &  5: Gives RAM and SWAP details.
Line6: To execute top command shortcuts(See below for the list of top command shortcuts ).
From Line7: dynamically displayed top process results.
 

Linux top Command Shortcut
 
l --To display or to hide load average line

t --To display or to hide task/cpu line

1 --To display or hide all other CPU's

m --to display or to hide RAM and SWAP details

s --To change the time interval for updating top results(value is in sec's)

R --To sort by PID number

u -- Press u then username to get only that user process details

P --To sort by CPU utilization 

M --To sort by RAM utilization 

c --To display or hide command full path

r --To renice a process, press r then the PID no then the renice value to renice a process.

k --To kill a process, press k then PID number then enter to kill a process
 
W --To save the modified configuration permanently.
 
q --To quit the top command. 
 
h --for getting help on top command
 
space -- immediately refresh output


!Enjoy 
Kuldeep Sharma