1: top - Process Activity Command
The top program provides a dynamic real-time view of a running system i.e. actual process activity. By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.
Commonly Used Hot Keys
The top command provides several useful hot keys:| Hot Key | Usage |
|---|---|
| t | Displays summary information off and on. |
| m | Displays memory information off and on. |
| A | Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system. |
| f | Enters an interactive configuration screen for top. Helpful for setting up top for a specific task. |
| o | Enables you to interactively select the ordering within top. |
| r | Issues renice command. |
| k | Issues kill command. |
| z | Turn on or off color/mono |
2: vmstat - System Activity, Hardware and System Information
The command vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
[root@NaN NaN]# vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 0 206052 117096 1177156 0 0 49 52 206 445 4 1 94 1 0
Display Memory Utilization Slabinfo
# vmstat -mGet Information About Active / Inactive Memory Pages
# vmstat -a3: w - Find Out Who Is Logged on And What They Are Doing
w command displays information about the users currently on the machine, and their processes.[root@NaN NaN]# w NaN
13:27:45 up 3:26, 2 users, load average: 0.00, 0.00, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
NaN tty1 :0 10:02 3:25m 3:12 0.00s pam: gdm-password
NaN pts/0 :0.0 12:44 0.00s 1.33s 1.52s gnome-terminal
4: uptime - Tell How Long The System Has Been Running
The uptime command can be used to see how long the server has been running. The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.[root@NaN NaN]# uptime
13:28:36 up 3:26, 2 users, load average: 0.00, 0.00, 0.00
5: ps - Displays The Processes
ps command will report a snapshot of the current processes. To select all processes use the -A or -e option:[root@NaN NaN]# ps -A
PID TTY TIME CMD
1 ? 00:00:00 init
2 ? 00:00:00 kthreadd
3 ? 00:00:00 migration/0
4 ? 00:00:00 ksoftirqd/0
5 ? 00:00:00 watchdog/0
6 ? 00:00:00 migration/1
7 ? 00:00:00 ksoftirqd/1
8 ? 00:00:00 watchdog/1
9 ? 00:00:00 events/0
10 ? 00:00:00 events/1
6: free - Memory Usage
The command free displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel.[root@NaN NaN]# free
total used free shared buffers cached
Mem: 2052376 1848564 203812 0 117924 1176184
-/+ buffers/cache: 554456 1497920
Swap: 4196348 0 4196348
7: iptraf - Real-time Network Statistics
The iptraf command is interactive colorful IP LAN monitor. It is an ncurses-based IP LAN monitor that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others. It can provide the following info in easy to read format:- Network traffic statistics by TCP connection
- IP traffic statistics by network interface
- Network traffic statistics by protocol
- Network traffic statistics by TCP/UDP port and by packet size
- Network traffic statistics by Layer2 address
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