Checking Resource Usage in Fedora (Linux)

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Donna Potter
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1 Lab 5C Checking Resource Usage in Fedora (Linux) Objective In this exercise, the student will learn how to check the resources on a Fedora system. This lab covers the following commands: df du top Equipment The following equipment is required for this exercise: A computer with Fedora v12 or greater installed. Scenario There is a server running Fedora (Linux) that has been running efficiently for a long time but the system resources might be reaching their limits. The technician decides to run a few of the commands to check the system resources to ensure that the system will continue to run properly. Procedures There are three basic Linux commands used to check and record the resource usage on a Linux system. 1

2 Step 1: The df Command (disk file system) 1. Login as the root user and open a terminal window. 2. To determine the amount of hard drive space that is being used by Linux, type: df To make the output of the df command easier to read, type: df h You will notice the output is easier for human to read. Explain to your instructor how much hard disk space is being used. Instructor Signature Step 2: The du Command (disk usage) 1. Remain logged in as the root user 2. The du command is useful in determining the size of any directory or file within a directory. To go to the /etc directory and determine the size of the directory and the size of the passwd file, type the following command sequence: cd /etc du du hs du hs passwd 2

3 The size of the /etc directory will be displayed. The size of the passwd file will be displayed. Explain to your instructor the size of the /etc directory and the size of the passwd file. Instructor signature Example of the du command 3

4 Step 3: The top Command 1. From a terminal type: top In the example below, the output shows the followings: CPU idle time=97.6% No. of user =3 No. of processes = 73 No. of processes sleeping =70 Memory used =125508K Memory free = 5196K 4

5 Example of the top command 2 Base on the output of your Linux system top command, explain to your instructor the CPU, User and memory parameters. Instructor signature 5

6 More about the Top command Top command provides a real-time look at what is happening with your system. Top produces so much output that a new user may get over whelmed with all that s presented and what it means. Let s take a look at Top one line at a time. The server has been flooded with http requests to create some load on the server. Top output: The first line in Top: 22:09:08 is the current time; up 14 min shows how long the system has been up for; 1 user how many users are logged in; load average: 0.21, 0.23, 0.30 the load average of the system (1minute, 5 minutes, 15 minutes). 6

7 Load average is an extensive topic and to understand its inner workings can be daunting. The simplest of definitions states that load average is the CPU utilization over a period of time. A load average of 1 means your CPU is being fully utilized and processes not having to wait to use a CPU. A load average above 1 indicates that processes need to wait and your system will be less responsive. If your load average is consistently above 3 and your system is running slow you may want to upgrade to more CPU s or a faster CPU. The second line in Top: Shows the number of processes and their current state. The third line in Top: Shows CPU utilization details. 9.5%us user processes are using 9.5%; 31.2%sy system processes are using 31.2%; 27.0%id percentage of available CPU; 7.6%wa time CPU is waiting for IO. When first analyzing the CPU(s) line in top look at the %id to see how much CPU is available. If %id is low then focus on %us, %sy, and %wa to determine what is using the CPU. The fourth and fifth lines in Top: Describes the memory usage. These numbers can be misleading k total is total memory in the system; K used is the part of the RAM that currently contains information; 88024k free is the part of RAM that contains no information; 25068K buffers and 85724k cached is the buffered and cached data for IO. So the actual amount of free RAM available for programs to use is: free + (buffers + cached) 7

8 88024k + (25068k k) = k How much RAM is being used by programs? The answer is: used (buffers + cached) k (25068k k) = 56776k The processes information: Top will display the process using the most CPU usage in descending order. Let s describe each column that represents a process. PID process ID of the process USER User who is running the process PR The priority of the process NI Nice value of the process (higher value indicates lower priority) VIRT The total amount of virtual memory used RES Resident task size SHR Amount of shared memory used S State of the task. Values are S (sleeping), D (uninterruptible sleep), R (running), Z (zombies), or T (stopped or traced) %CPU Percentage of CPU used %MEM Percentage of Memory used TIME+ Total CPU time used COMMAND Command issued 8

9 Interacting with Top Now that we are able to understand the output from Top lets learn how to change the way the output is displayed. Just press the following key while running top and the output will be sorted in real time. M Sort by memory usage P Sort by CPU usage T Sort by cumulative time z Color display k Kill a process q quit If we want to kill the process with PID 3161, then press k and a prompt will ask you for the PID number, and enter Command Line Parameters with Top You can control what top displays by issuing parameters when you run top. - d Controls the delay between refreshes - p Specify the process by PID that you want to monitor -n Update the display this number of times and then exit If we want to only monitor the http process with a PID of 3166 If we want to change the delay between refreshes to 5 seconds A Graphical View: Gnome System Monitor - Real-time Systems Reporting and Graphing The System Monitor application enables you to display basic system information and monitor system processes, usage of system resources, and file systems. You can also use System Monitor to modify the behavior of your system. Although not as powerful as the KDE System Guard, it provides the basic information which may be useful for new users: Displays various basic information about the computer's hardware and software. 9

Linux Kernel version GNOME version Hardware Installed memory Processors and speeds System Status Currently available disk space Processes Memory and swap space Network usage File Systems Lists all

10 Linux Kernel version GNOME version Hardware Installed memory Processors and speeds System Status Currently available disk space Processes Memory and swap space Network usage File Systems Lists all mounted filesystems along with basic information about each. Gnome System Monitor application The The tool is located at under Applications > System Tools > System Monitor. Explain to your instructor the graphical output generated by the system monitor tool. Instructor Signature 10

APACHE TROUBLESHOOTING. Or, what to do when your vhost won t behave

APACHE TROUBLESHOOTING. Or, what to do when your vhost won t behave APACHE TROUBLESHOOTING Or, what to do when your vhost won t behave ABOUT THE CLASS 24 hours over three days Very Short Lecture and Lots of Labs Hours: 8:30am - 5:00pm Lunch: 11:45am - 1:00pm ABOUT THE