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Tag: top
4 Top Command Howto on Linux RHEL 6/CentOS 6
In this article, i will help you to explore most frequently used top commands that linux system administrator use when analyzing the linux performance and use for daily system administrative jobs. Top command displays system summary information such as tasks currently being managed by the Linux kernel, displays ongoing look at processor activity in real time and will displays a listing of the most CPU-intensive tasks on the system. It also will show the processor and memory are being used and other information like running processes. It will help you to summarize how much of your system’s resources are taking up.
1. How to display top command result :
[root@rhel6 ~]# top
This command will show information like tasks, memory, cpu load average, swap and number of users. Press ‘q’ to quit window.
2. How to display selected user using top -u :
[root@rhel6 ~]# top -u apache
3. How to display specific process with given PIDs Using top -p(e.g PID 2449, 2450) :
[root@rhel6 ~]# top -p 2449,2450
4. How to quit top command after a specified number of iterations :
[root@rhel6 ~]# top -n 10
This top command will automatically exit after 10 number of repetition.
How to Track System Activity With top Command on Linux CentOS 5/CentOS 6/RHEL 5/ RHEL 6 server – System Performance
Top command is utility to monitor system activity interactively. When you run top from shell window, it will display all the activity processes and updates the screen. In this post i will show the usage of top command on CentOS 5/CentOS 6/RHEL 5/ RHEL 6 server to keep track system activity and to optimize the system performance.
Display top command on RHEL 6 :
[root@rhel6 ~]# top
top - 18:54:19 up 13:29, 2 users, load average: 0.00, 0.00, 0.00
Tasks: 93 total, 1 running, 90 sleeping, 2 stopped, 0 zombie
Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1031320k total, 225804k used, 805516k free, 31120k buffers
Swap: 2064376k total, 0k used, 2064376k free, 116716k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1375 root 20 0 97768 9796 5768 S 0.3 0.9 0:03.43 httpd
3974 root 20 0 2632 1076 868 R 0.3 0.1 0:00.08 top
1 root 20 0 2828 1392 1196 S 0.0 0.1 0:01.81 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 watchdog/0
6 root 20 0 0 0 0 S 0.0 0.0 0:00.25 events/0
7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuset
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns
10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm
12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 sync_supers
13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 bdi-default
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/0
15 root 20 0 0 0 0 S 0.0 0.0 0:00.02 kblockd/0
16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid
17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify
18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplug
19 root 20 0 0 0 0 S 0.0 0.0 0:00.01 ata/0
20 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_aux
21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksuspend_usbd
22 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khubd
23 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kseriod
25 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khungtaskd
26 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kswapd0
27 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 aio/0
29 root 20 0 0 0 0 S 0.0 0.0 0:00.00 crypto/0
34 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pciehpd
36 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
37 root 20 0 0 0 0 S 0.0 0.0 0:00.00 usbhid_resumer
67 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kstriped
267 root 20 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
268 root 20 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_1
279 root 20 0 0 0 0 S 0.0 0.0 0:00.20 mpt_poll_0
Display top command on CentOS 5.7 :
[root@CentOS57 ~]# top
top - 18:57:39 up 10:04, 2 users, load average: 0.00, 0.00, 0.00
Tasks: 73 total, 1 running, 70 sleeping, 2 stopped, 0 zombie
Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1034700k total, 86916k used, 947784k free, 7292k buffers
Swap: 2096472k total, 0k used, 2096472k free, 36104k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 15 0 2160 676 584 S 0.0 0.1 0:00.93 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 10 -5 0 0 0 S 0.0 0.0 0:00.00 events/0
5 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 khelper
6 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kthread
9 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 kblockd/0
10 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kacpid
173 root 17 -5 0 0 0 S 0.0 0.0 0:00.00 cqueue/0
176 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 khubd
178 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 kseriod
244 root 21 0 0 0 0 S 0.0 0.0 0:00.00 khungtaskd
245 root 22 0 0 0 0 S 0.0 0.0 0:00.00 pdflush
246 root 15 0 0 0 0 S 0.0 0.0 0:00.01 pdflush
247 root 17 -5 0 0 0 S 0.0 0.0 0:00.00 kswapd0
248 root 17 -5 0 0 0 S 0.0 0.0 0:00.00 aio/0
466 root 11 -5 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
492 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 mpt_poll_0
493 root 19 -5 0 0 0 S 0.0 0.0 0:00.00 mpt/0
494 root 19 -5 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
497 root 19 -5 0 0 0 S 0.0 0.0 0:00.00 ata/0
498 root 19 -5 0 0 0 S 0.0 0.0 0:00.00 ata_aux
505 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kstriped
514 root 10 -5 0 0 0 S 0.0 0.0 0:00.17 kjournald
544 root 11 -5 0 0 0 S 0.0 0.0 0:00.00 kauditd
577 root 21 -4 3004 1468 504 S 0.0 0.1 0:00.62 udevd
1730 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kmpathd/0
1731 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 kmpath_handlerd
1790 root 11 -5 0 0 0 S 0.0 0.0 0:00.00 kjournald
1868 root 13 -5 0 0 0 S 0.0 0.0 0:00.00 iscsi_eh
1896 root 18 -5 0 0 0 S 0.0 0.0 0:00.00 cnic_wq
1911 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 ib_addr
1918 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 ib_mcast
1919 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 ib_inform
1920 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 local_sa
1923 root 20 -5 0 0 0 S 0.0 0.0 0:00.00 iw_cm_wq
By default, top will update its screen in every seconds. You can change this interval by using d seconds options as below :
To update the screen every 5 seconds, run the “top d 5” command :
[root@rhel6 ~]# top d 5 top - 18:56:51 up 13:32, 2 users, load average: 0.00, 0.00, 0.00 Tasks: 94 total, 1 running, 90 sleeping, 3 stopped, 0 zombie Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.7%id, 0.2%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1031320k total, 226064k used, 805256k free, 31136k buffers Swap: 2064376k total, 0k used, 2064376k free, 116716k cached
To update the screen every 10 seconds, run the “top d 10” command :
[root@rhel6 ~]# top d 10 top - 18:57:21 up 13:32, 2 users, load average: 0.00, 0.00, 0.00 Tasks: 95 total, 1 running, 90 sleeping, 4 stopped, 0 zombie Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.7%id, 0.2%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1031320k total, 226448k used, 804872k free, 31144k buffers Swap: 2064376k total, 0k used, 2064376k free, 116716k cached
The screen updates every 5 to 20 seconds interval is more usefull tha the default setting, 1 second. This because update every 1 second will lists itself in its own output as the main resource consumer. If you press the h key while top is running, you will see the following output screen :
