Transcript Linux+ Guide to Linux Certification Chapter Fourteen

Linux+ Guide to Linux Certification
Chapter Fourteen
Troubleshooting and
Performance
Objectives
• Describe and outline common troubleshooting
procedures
• Identify good troubleshooting practices
• Effectively troubleshoot common hardware-related
problems
• Effectively troubleshoot common software-related
problems
• Monitor system performance using command-line and
graphical utilities
• Understand the purpose and usage of kernel modules
Troubleshooting Methodology
Figure 14-1:
The maintenance
cycle
Troubleshooting Methodology
• Monitoring
– Process by which system areas are observed for
problems or irregularities
• Proactive maintenance
– Measure taken to reduce future system problems
• Reactive maintenance
– Measure taken when system problems arise
Troubleshooting Methodology
• Documentation
– System information that is stored in a log book
for future references
• Troubleshooting procedures
– The tasks performed when solving system
problems
Troubleshooting Methodology
Figure 14-2:
Common
troubleshooting
procedures
Troubleshooting Methodology
• Two golden rules to guide you during any
troubleshooting process:
– Prioritize problems
• Prioritize the problems according to severity and spend a
reasonable amount of time on each problem given its
priority
– Try to solve the root of the problem
• To avoid missing the underlying cause of any problem, try
to justify why a certain solution is successful
Hardware-Related Problems
Figure 14-3:
The KDE
Control
Center
Hardware-Related Problems
• The absence of a device driver will also
prevent the operating system from using the
associated hardware devices
• Kudzu program
– Program used to detect and install support for
new hardware
Hardware-Related Problems
Figure 14-4: The kudzu welcome screen
Hardware-Related Problems
Figure 14-5: Configuring new hardware using kudzu
Hardware-Related Problems
• If the hard disk that contains the / filesystem
fails, then perform the following steps:
– Power down the computer and replace the failed
hard disk
– Reinstall Linux on the new hard disk
– Restore the original configuration and data files
using a back-up utility
Software-Related Problems:
Application-Related Problems
• Dependencies
– The prerequisites required for program execution
such as shared libraries or other packages
• ldd command
– Command used to display the shared libraries
used by a certain program
Software-Related Problems:
Application-Related Problems
• ldconfig command
– Command that updates the /etc/ld.so.conf and
/etc/ld.so.cache files
• /etc/ld.so.conf files
– File that contains a list of directories that contain
shared libraries
• /etc/ld.so.cache file
– File that contains the location of shared library
files
Software-Related Problems:
Application-Related Problems
• Filehandles
– Connection that a program makes to files on a
filesystem
• unlimit command
– Command used to modify process limit
parameters in the current shell
• /var/log directory
– Directory that contains most system log files
Software-Related Problems:
OS-Related Problems
• Most software-related problems are related to
the operating system itself
– These typically involve problems with boot
loaders, filesystems, and serial devices
• mkbootdisk command
– Command used to create a boot floppy diskette
Software-Related Problems:
OS-Related Problems
Figure 14-6: The Red Hat Linux installation welcome screen
Software-Related Problems:
OS-Related Problems
Figure 14-7: Obtaining a shell in rescue mode
Software-Related Problems:
OS-Related Problems
Figure 14-8: The command-line shell used in rescue mode
Software-Related Problems:
OS-Related Problems
Table 14-1: Common keywords used with the setserial utility
Performance Monitoring
• Jabbering
– Process by which failing hardware components
send large amounts of information to the CPU
• Bus mastering
– Process by which peripheral components perform
tasks normally executed by the CPU
Performance Monitoring
• To ease identification of performance
problems, you should run performance
utilities on a healthy Linux system on a
regular basis during normal business hours
and record results in a system log book
• Baseline
– A measure of normal system activity
Monitoring Performance with
sysstat Utilities
• System Statistics (sysstat) package
– Software package that contains common
performance monitoring utilities such as mpstat,
iostat, sar, and isag
• Multiple Processor Statistics (mpstat) utility
– Command that displays CPU statistics
Monitoring Performance with
sysstat Utilities
• Input/Output Statistics (iostat) command
– Command that displays Input/Output statistics for
block devices
• System Activity Reporter (sar) command
– Command that displays various system statistics
Monitoring Performance with
sysstat Utilities
Table 14-2: Common options to the sar command
Monitoring Performance with
sysstat Utilities
Table 14-2 (continued): Common options to the sar command
Monitoring Performance with
sysstat Utilities
• If there are a large number of pages being sent to
and taken from the swap partition, then the
system will suffer from slower performance
– To remedy this, you could add more physical memory
(RAM) to the system
• Interactive System Activity Grapher (isag)
command
– Command used to graph system performance
information stored in the /var/log/sa directory
Monitoring Performance with
sysstat Utilities
Figure 14-9: Choosing a file to view using the System Activity Grapher
Monitoring Performance with
sysstat Utilities
Figure 14-10: Choosing statistics using the System Activity Grapher
Monitoring Performance with
sysstat Utilities
Figure 14-11: Viewing user statistics using the System Activity Grapher
Other Performance Monitoring
Utilities
• free command
– Command used to display memory and swap
statistics
• vmstat command
– Command used to display memory, CPU, and
swap statistics
Kernel Modules
• Many device drivers and kernel features are
compiled into the kernel
– However, these may also be inserted into the
kernel as modules to reduce the size of the kernel
• It is good form to compile standard device
support into the kernel and leave support for
other devices and features as modules
Kernel Modules
• insmod command
– Command used to insert a module into the Linux
kernel
• modprobe command
– Command used to insert a module and all necessary
prerequisites modules into the Linux kernel
• lsmod command
– Command that lists modules currently used by the
Linux kernel
Kernel Modules
• rmmod command
– Command that removes a module from the Linux
kernel
• /etc/modules.conf file
– File used to load and alias modules at system
initialization
• /etc/rc.d/rc.local file
– File used to load modules at system initialization
Compiling a New Linux Kernel
• To gain certain hardware or kernel support, it
may be necessary to recompile the current
kernel with different features or download the
source code for a newer kernel and compile it
• /usr/src/linux
– The directory that contains source code for the
Linux kernel during compilation
Compiling a New Linux Kernel
Figure 14-12: The make menuconfig interface
Compiling a New Linux Kernel
Figure 14-13: The make xconfig interface
Compiling a New Linux Kernel
Figure 14-14: Configuring code maturity level options
Compiling a New Linux Kernel
Figure 14-15: Configuring USB support
Patching the Linux Kernel
• To install a more current Linux kernel
version, you normally download the source
code for that kernel and place it in a directory
that will be referenced by /usr/src/linux
• Patch command
– Command used to supply a patch to the Linux
kernel source code
Chapter Summary
• After installation, Linux administrators monitor the
system, perform proactive and reactive maintenance,
and document important system information
• Common troubleshooting procedures involve
collecting data to isolate and determine the cause of
system problems, as well as implementing and
testing solutions that can be documented for future
use
• System problems may be categorized as hardwareor software-related
Chapter Summary
• IRQ conflicts, invalid hardware settings,
absence of kernel support, and hard disk
failure are common hardware-related
problems on Linux systems
• Software-related system problems may be
further categorized as application-related or
operating system-related
• System performance is affected by a variety
of hardware and software factors
Chapter Summary
• Using performance monitoring utilities to
create a baseline is helpful when diagnosing
performance problems in the future
• System features and hardware support may be
compiled into the Linux kernel or provided by
a kernel module
• You may compile a Linux kernel with only
the necessary features and support in order to
increase system performance