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Chapter 6

Troubleshooting the Operating System Part 1. Chapter 6. Identifying and Locating Symptoms and Problems. Hardware Problems. Hardware errors do not crash the system, they leave a message prefixed by the word oops in the log file / var /log/messages. Kernel Problems.

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Chapter 6

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  1. Troubleshooting the Operating System Part 1 Chapter 6

  2. Identifying and Locating Symptoms and Problems

  3. Hardware Problems • Hardware errors do not crash the system, they leave a message prefixed by the word oops in the log file /var/log/messages.

  4. Kernel Problems • Released Linux kernels are remarkably stable, unless experimental versions are used or individual modifications are made. • Loadable kernel modules are considered part of the kernel as well, at least for the time period they are loaded. • Sometimes these can cause difficulties, too. • The good news with modules is that they can be uninstalled and replaced with fixed versions while the system is still running.

  5. Configuration • Configuration problems tend to affect whole subsystems, such as the graphics, printing, or networking subsystems. • If the system is rebooted and a remote file system that was once present is not, the first place to look is in the configuration file /etc/fstab to see if the file system is supposed to be mounted at boot time.

  6. Using System Utilities and System Status Tools • Linux operating systems provide various system utilities and system status tools. • The setserial utility provides information and set options for the serial ports on the system. • The lpq command helps resolve printing problems. • This command will display all the jobs that are waiting to be printed.

  7. Unresponsive Programs and Processes • Sometimes there are programs and processes that for various reasons can become unresponsive or “lock up”. • Sometimes just the process itself will lock up and other times can cause the entire system to become unresponsive. • One method of identifying and locating the unresponsive program and effectively troubleshooting the problem is to kill or restart the process or program.

  8. Examining Log Files • Some of the more important log files on a Linux system are the /var/log/messages, /var/log/secure, and the /var/log/syslog log files. • The system’s log files can be used to monitor system loads such as how many pages a web server has served. • They can also check for security breaches such as intrusion attempts, verify that the system is functioning properly, and note any errors that might be generated by software or programs.

  9. Examining Log Files • There are several different types of information that are good to know, which will make identifying problems using the log files a little easier. • Some of these are listed below: • Monitoring System Loads • Intrusion Attempts and Detection • Normal System Functioning • Missing Entries • Error Messages

  10. The dmesg Command • The dmesg command can be used to display the recent kernel messages, also known as the kernel ring buffer. • These messages contain information about the hardware installed in the system and the drivers. • The information in these messages relates to whether the drivers are being loaded successfully and what devices the drivers are controlling.

  11. Troubleshooting Problems Based on User Feedback • There are several different types of problems that users report. • Some of the most common ones are: • Login Problems • File Permission Problems • Removable Media Problems • E-mail Problems • Program Errors • Shutdown Problems

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