{"id":2196,"date":"2012-03-11T11:50:08","date_gmt":"2012-03-11T03:50:08","guid":{"rendered":"https:\/\/webhostinggeeks.com\/howto\/?p=2196"},"modified":"2023-06-23T12:51:52","modified_gmt":"2023-06-23T12:51:52","slug":"how-to-track-system-activity-with-top-command-on-linux-centos-5centos-6rhel-5-rhel-6-server-system-performance","status":"publish","type":"post","link":"https:\/\/webhostinggeeks.com\/howto\/how-to-track-system-activity-with-top-command-on-linux-centos-5centos-6rhel-5-rhel-6-server-system-performance\/","title":{"rendered":"How to Track System Activity with “top” Command on Linux CentOS (5\/6) and RHEL (5\/6)"},"content":{"rendered":"

In server administration, it’s crucial to have a comprehensive understanding of your system’s activity. This knowledge allows you to optimize performance, troubleshoot issues, and ensure the smooth operation of your web server<\/a>. <\/p>\n

One of the most effective tools for this purpose is the top command, a utility that provides a dynamic, real-time view of a running system. It displays system summary information as well as a list of tasks currently managed by the Linux kernel.<\/p>\n

This guide will walk you through the usage of the top command on CentOS 5\/CentOS 6\/RHEL 5\/ RHEL 6 servers.<\/p>\n

For a more in-depth understanding of web server types, you may want to explore our articles on Apache<\/a>, Nginx<\/a>, and LiteSpeed<\/a>. Understanding the type of server you’re working with can greatly enhance your ability to optimize and troubleshoot it.<\/p>\n

Using the `top` Command<\/h2>\n

The top command is a utility that allows you to monitor system activity interactively. When you run top from a shell window, it displays all active processes and updates the screen in real time. This is particularly useful for keeping track of system activity and optimizing system performance.<\/p>\n

To display the top command on RHEL 6, you would use the following command:<\/p>\n

\r\n[root@rhel6 ~]# top\r\n<\/pre>\n
This will display a variety of information, including the total number of tasks, the number of running tasks, CPU usage, memory usage, and a list of all active processes.<\/p>\n
\r\n[root@rhel6 ~]# top\r\ntop - 18:54:19 up 13:29,  2 users,  load average: 0.00, 0.00, 0.00\r\nTasks:  93 total,   1 running,  90 sleeping,   2 stopped,   0 zombie\r\nCpu(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\r\nMem:   1031320k total,   225804k used,   805516k free,    31120k buffers\r\nSwap:  2064376k total,        0k used,  2064376k free,   116716k cached\r\n\r\n  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND\r\n 1375 root      20   0 97768 9796 5768 S  0.3  0.9   0:03.43 httpd\r\n 3974 root      20   0  2632 1076  868 R  0.3  0.1   0:00.08 top\r\n    1 root      20   0  2828 1392 1196 S  0.0  0.1   0:01.81 init\r\n    2 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kthreadd\r\n    3 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 migration\/0\r\n    4 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ksoftirqd\/0\r\n    5 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 watchdog\/0\r\n    6 root      20   0     0    0    0 S  0.0  0.0   0:00.25 events\/0\r\n    7 root      20   0     0    0    0 S  0.0  0.0   0:00.00 cpuset\r\n    8 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khelper\r\n    9 root      20   0     0    0    0 S  0.0  0.0   0:00.00 netns\r\n   10 root      20   0     0    0    0 S  0.0  0.0   0:00.00 async\/mgr\r\n   11 root      20   0     0    0    0 S  0.0  0.0   0:00.00 pm\r\n   12 root      20   0     0    0    0 S  0.0  0.0   0:00.00 sync_supers\r\n   13 root      20   0     0    0    0 S  0.0  0.0   0:00.00 bdi-default\r\n   14 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kintegrityd\/0\r\n   15 root      20   0     0    0    0 S  0.0  0.0   0:00.02 kblockd\/0\r\n   16 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kacpid\r\n   17 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kacpi_notify\r\n   18 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kacpi_hotplug\r\n   19 root      20   0     0    0    0 S  0.0  0.0   0:00.01 ata\/0\r\n   20 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ata_aux\r\n   21 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ksuspend_usbd\r\n   22 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khubd\r\n   23 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kseriod\r\n   25 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khungtaskd\r\n   26 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kswapd0\r\n   27 root      25   5     0    0    0 S  0.0  0.0   0:00.00 ksmd\r\n   28 root      20   0     0    0    0 S  0.0  0.0   0:00.00 aio\/0\r\n   29 root      20   0     0    0    0 S  0.0  0.0   0:00.00 crypto\/0\r\n   34 root      20   0     0    0    0 S  0.0  0.0   0:00.00 pciehpd\r\n   36 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kpsmoused\r\n   37 root      20   0     0    0    0 S  0.0  0.0   0:00.00 usbhid_resumer\r\n   67 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kstriped\r\n  267 root      20   0     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_0\r\n  268 root      20   0     0    0    0 S  0.0  0.0   0:00.00 scsi_eh_1\r\n  279 root      20   0     0    0    0 S  0.0  0.0   0:00.20 mpt_poll_0\r\n<\/pre>\n
Adjusting the Update Interval<\/h2>\n
By default, top will update its screen every second. However, you can change this interval by using the d option followed by the number of seconds you want as the new interval. For example, to update the screen every 5 seconds, you would use the following command:<\/p>\n
\r\n[root@rhel6 ~]# top d 5\r\n<\/pre>\n
\r\n[root@rhel6 ~]# top d 5\r\ntop - 18:56:51 up 13:32,  2 users,  load average: 0.00, 0.00, 0.00\r\nTasks:  94 total,   1 running,  90 sleeping,   3 stopped,   0 zombie\r\nCpu(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\r\nMem:   1031320k total,   226064k used,   805256k free,    31136k buffers\r\nSwap:  2064376k total,        0k used,  2064376k free,   116716k cached\r\n<\/pre>\n
To update the screen every 10 seconds, you would use:<\/p>\n
\r\n[root@rhel6 ~]# top d 10\r\n<\/pre>\n
\r\n[root@rhel6 ~]# top d 10\r\ntop - 18:57:21 up 13:32,  2 users,  load average: 0.00, 0.00, 0.00\r\nTasks:  95 total,   1 running,  90 sleeping,   4 stopped,   0 zombie\r\nCpu(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\r\nMem:   1031320k total,   226448k used,   804872k free,    31144k buffers\r\nSwap:  2064376k total,        0k used,  2064376k free,   116716k cached\r\n<\/pre>\n
Updating the screen at an interval of 5 to 20 seconds is often more useful than the default setting of 1 second. This is because when top updates every second, it often lists itself in its own output as the main resource consumer.<\/p>\n
Getting Help<\/h2>\n
If you need help while using top, you can press the h key while top is running to display a help screen.<\/p>\n
\r\n  Z,B,E,e   Global: 'Z' colors; 'B' bold; 'E'\/'e' summary\/task memory scale\r\n  l,t,m     Toggle Summary: 'l' load avg; 't' task\/cpu stats; 'm' memory info\r\n  0,1,2,3,I Toggle: '0' zeros; '1\/2\/3' cpus or numa node views; 'I' Irix mode\r\n  f,F,X     Fields: 'f'\/'F' add\/remove\/order\/sort; 'X' increase fixed-width\r\n\r\n  L,&,<,> . Locate: 'L'\/'&' find\/again; Move sort column: '<'\/'>' left\/right\r\n  R,H,V,J . Toggle: 'R' Sort; 'H' Threads; 'V' Forest view; 'J' Num justify\r\n  c,i,S,j . Toggle: 'c' Cmd name\/line; 'i' Idle; 'S' Time; 'j' Str justify\r\n  x,y     . Toggle highlights: 'x' sort field; 'y' running tasks\r\n  z,b     . Toggle: 'z' color\/mono; 'b' bold\/reverse (only if 'x' or 'y')\r\n  u,U,o,O . Filter by: 'u'\/'U' effective\/any user; 'o'\/'O' other criteria\r\n  n,#,^O  . Set: 'n'\/'#' max tasks displayed; Show: Ctrl+'O' other filter(s)\r\n  C,...   . Toggle scroll coordinates msg for: up,down,left,right,home,end\r\n\r\n  k,r       Manipulate tasks: 'k' kill; 'r' renice\r\n  d or s    Set update interval\r\n  W,Y       Write configuration file 'W'; Inspect other output 'Y'\r\n  q         Quit\r\n<\/pre>\n
Commands Mentioned<\/h2>\n