Guide to Linux Installation and Administration, 2e1 Chapter 10 Managing System Resources

Guide to Linux Installation and Administration, 2e

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Chapter 10

Managing System Resources


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Objectives

In this chapter, you will:

• Access the /proc file system to manage system status

• Control how processes use system resources

• Track physical and virtual memory usage

• Locate and relieve system bottlenecks

• Manage system logs


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Viewing System Status in /proc

• The /proc file system is a specialized file system that lets you view and control system resources such as processes, memory, and kernel networking parameters

• When you query a filename in /proc, the Linux kernel responds with live information about the status of a process, memory, or other resource


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Viewing Device Information


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System Information in the KDE Control Center


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Viewing Process Information

• The /proc file system contains detailed information about each process running on Linux

• Before you can access information in /proc regarding a specific process, you need to find the process’s PID number

• To find the PID for a running process, use the ps command


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Managing Processes

• To manage your system effectively, you will often need to display detailed information about specific processes

• The ps command has many options to select processes to be included in the command output

• You can select what information is displayed about each process


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Ps Options Used to Select Processes


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Combination Process Information Fields Available from ps


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Process Information Fields Available from ps


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Process Information Fields Available from ps (continued)


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Changing Process Priorities

• Each process in Linux is assigned a priority, called a nice level

• The root user can change the priority of any process; other users can raise the nice level of processes they have started

• The nice and renice commands set a process’s nice level; other command-line and graphical programs also let you change a process’s nice level


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Viewing Processor Usage with top

• The top command lists processes according to how much CPU time they are using

• The output of top is updated every few seconds• The top command can also be used to control

processes by sending them signals


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Interactive Commands in top


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Using Graphical Process Managing Tools

• KDE System Guard and the Gnome System Monitor are two powerful graphical process management utilities

• Graphical process managing tools display many fields of information about each process and can be used to send signals to a process


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The KDE System Guard Utility


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The Gnome System Monitor Utility


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Actively Monitoring the CPU Load

• You can display a small CPU load monitor on the Panel of your desktop to keep an eye on system load

• When the CPU load is consistently high, you can begin checking for processes that may need attention


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A CPU Load Monitor


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Managing Memory

• The Gnome System Monitor provides memory management features

• You can manage physical memory (RAM) and virtual memory

• The Linux kernel and Linux programs can only interact with information stored in RAM


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Understanding Shared Libraries

• Shared libraries let many Linux programs access the same programming functionality without loading it into memory multiple times

• Dynamically linked applications use shared libraries

• Statically linked applications have a copy of the programming libraries they need built into the application itself


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Understanding Paged Memory

• A page of memory is a block of 4 KB of RAM

• The Linux kernel moves data to and from swap space in pages


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Tracking Memory Usage

• The free command displays information about RAM and virtual memory usage

• All the information displayed by free is in kilobytes

• A buffer is memory used by an application for data storage


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Memory Usage


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The Preferences Dialog Box in the Gnome System Monitor


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Tracking Per-Application Memory Use

• You can use the Gnome System Monitor to view how a single process is using memory

• Right-click on any process and choose Memory Maps from the pop-up menu


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Graphical Memory Map Tab for a Single Process


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Viewing Virtual Memory Information

• You can use the vmstat command to view detailed information about how swap space is used

• When vmstat is run as a regular command, its output is based on information averaged over time since the system was booted


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Locating System Bottlenecks

• A bottleneck is the part of a computer system that significantly slows down completion of the task at hand

• Bottlenecks reduce system performance when one component, such as a slow network connection or disk drive, can’t keep up with the rest of the system


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Identifying and Removing Bottlenecks

• Use various utilities• Test many programs• Review performance measurements and

system status


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Using Benchmarks

• To identify bottlenecks a benchmark program can be used

• Benchmarks provide a numeric measurement of one aspect of system performance


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Managing System Logs

• Log files record the activities of Linux programs

• The main system log used by the kernel and many daemons is /var/log/messages

• A message is a description of what is happening within a program


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Commonly Logged Events and Their Log Files


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The syslogd and klogd Daemons

• Any program running on Linux can call the shared programming function syslog and pass it a message

• syslogd watches for messages submitted by programs

• The klogd daemon (kernel logging daemon) watches for messages submitted by the Linux kernel


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How syslogd and klogd Work together to Process Log Messages


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Configuring the System Log

• Both syslogd and klogd rely on a single configuration file: /etc/syslog.conf

• Each line in syslog.conf defines a set of messages and what action to take with those messages

• Messages are defined using a selector, which is made up of a facility and a priority

• The facility defines the type of program that generated the message

• The priority defines the severity or type of message


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The Facilities


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The Priorities


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The Actions

• Once you set up a selector (consisting of a facility and a priority), you can assign an action to that selector

• The action determines what syslogd and klogd do with the messages defined by the selector


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Configuration File Syntax


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Using the logger Utility

• The logger utility lets you send a message to the system logging daemon

• You can use the logger utility from a command line or from a script

• You can specify selectors with the logger command


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Analyzing Log Files

• Log files contain a valuable record of what has occurred on your Linux system

• A system administrator should regularly check log files for indications of trouble

• You can use standard Linux tools like grep to search for information in the log files


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Interpreting Sample Log File Entries


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Rotating Log Files

• A common log rotation system stores log files for a month, with a separate archive file for each week

• Red Hat Linux provides a utility called logrotate to manage many types of log files

• The configuration file /etc/logrotate.conf defines how log files are rotated


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Summary

• The /proc file system lets you view details about the kernel, running processes, and other system information

• You can view process information using /proc or using the ps and top commands

• Each process in Linux is assigned a priority, called a nice level

• The nice and renice commands set a process’s nice level

• KDE System Guard and the Gnome System Monitor display information about each process and can be used to send signals to a process


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Summary

• The Linux kernel moves data to and from swap space in pages—4 KB pieces

• The free and vmstat commands display information about RAM and virtual memory usage

• Bottlenecks reduce system performance, but benchmarks can help identify bottlenecks

• System and kernel messages are logged by the syslogd and klogd daemons using the configuration in /etc/syslog.conf

• Log files must be maintained by rotating them using the logrotate command

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Guide to Linux Installation and Administration, 2e1 Chapter 10 Managing System Resources