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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Process Information Fields Available
from ps
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Process Information Fields Available
from ps (continued)
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Combination Process Information
Fields Available from ps
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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
Identifying and Removing Bottlenecks
• Use various utilities
• Test many programs
• Review performance measurements and
system status
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Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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Valued Gateway
Client:
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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