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Chapter 10

Chapter 10. Managing System Resources. 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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Chapter 10

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  1. Chapter 10 Managing System Resources Guide to Linux Installation and Administration, 2e

  2. 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 Guide to Linux Installation and Administration, 2e

  3. 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 Guide to Linux Installation and Administration, 2e

  4. Viewing Device Information Guide to Linux Installation and Administration, 2e

  5. System Information in the KDE Control Center Guide to Linux Installation and Administration, 2e

  6. 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 Guide to Linux Installation and Administration, 2e

  7. 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 Guide to Linux Installation and Administration, 2e

  8. Ps Options Used to Select Processes Guide to Linux Installation and Administration, 2e

  9. Combination Process Information Fields Available from ps Guide to Linux Installation and Administration, 2e

  10. Process Information Fields Available from ps Guide to Linux Installation and Administration, 2e

  11. Process Information Fields Available from ps (continued) Guide to Linux Installation and Administration, 2e

  12. 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 Guide to Linux Installation and Administration, 2e

  13. 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 Guide to Linux Installation and Administration, 2e

  14. Interactive Commands in top Guide to Linux Installation and Administration, 2e

  15. 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 Guide to Linux Installation and Administration, 2e

  16. The KDE System Guard Utility Guide to Linux Installation and Administration, 2e

  17. The Gnome System Monitor Utility Guide to Linux Installation and Administration, 2e

  18. 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 Guide to Linux Installation and Administration, 2e

  19. A CPU Load Monitor Guide to Linux Installation and Administration, 2e

  20. 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 Guide to Linux Installation and Administration, 2e

  21. 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 Guide to Linux Installation and Administration, 2e

  22. 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 Guide to Linux Installation and Administration, 2e

  23. 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 Guide to Linux Installation and Administration, 2e

  24. Memory Usage Guide to Linux Installation and Administration, 2e

  25. The Preferences Dialog Box in the Gnome System Monitor Guide to Linux Installation and Administration, 2e

  26. 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 Guide to Linux Installation and Administration, 2e

  27. Graphical Memory Map Tab for a Single Process Guide to Linux Installation and Administration, 2e

  28. 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 Guide to Linux Installation and Administration, 2e

  29. 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 Guide to Linux Installation and Administration, 2e

  30. Identifying and Removing Bottlenecks • Use various utilities • Test many programs • Review performance measurements and system status Guide to Linux Installation and Administration, 2e

  31. Using Benchmarks • To identify bottlenecks a benchmark program can be used • Benchmarks provide a numeric measurement of one aspect of system performance Guide to Linux Installation and Administration, 2e

  32. 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 Guide to Linux Installation and Administration, 2e

  33. Commonly Logged Events and Their Log Files Guide to Linux Installation and Administration, 2e

  34. 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 Guide to Linux Installation and Administration, 2e

  35. How syslogd and klogd Work together to Process Log Messages Guide to Linux Installation and Administration, 2e

  36. 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 Guide to Linux Installation and Administration, 2e

  37. The Facilities Guide to Linux Installation and Administration, 2e

  38. The Priorities Guide to Linux Installation and Administration, 2e

  39. 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 Guide to Linux Installation and Administration, 2e

  40. Configuration File Syntax Guide to Linux Installation and Administration, 2e

  41. 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 Guide to Linux Installation and Administration, 2e

  42. 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 Guide to Linux Installation and Administration, 2e

  43. Interpreting Sample Log File Entries Guide to Linux Installation and Administration, 2e

  44. 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 Guide to Linux Installation and Administration, 2e

  45. 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 Guide to Linux Installation and Administration, 2e

  46. 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 Guide to Linux Installation and Administration, 2e

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