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Chapter 13: System And Kernel Management

Chapter 13: System And Kernel Management. The Complete Guide to Linux System Administration. Objectives. Establish a Linux backup strategy Configure and review system log files Understand the use of kernel modules and the features of a high-end kernel Upgrade and recompile the Linux kernel.

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Chapter 13: System And Kernel Management

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  1. Chapter 13:System And Kernel Management The Complete Guide to Linux System Administration

  2. Objectives • Establish a Linux backup strategy • Configure and review system log files • Understand the use of kernel modules and the features of a high-end kernel • Upgrade and recompile the Linux kernel The Complete Guide to Linux System Administration

  3. Backing Up a Linux System • Backup • Copy of data on computer system • Form of insurance The Complete Guide to Linux System Administration

  4. Designing a Backup Strategy • Backup plan • Written document that outlines: • When and how files are backed up • How files are stored • How files are restored • Backup media • Item that holds backed-up data • Restore data • Copy from backup media to file system The Complete Guide to Linux System Administration

  5. Designing a Backup Strategy (continued) • Backup plan questions • What files should be backed up? • Who will back up files? • Where are files located? • How should backups be performed? • Must you be able to restore data within a specific period of time? The Complete Guide to Linux System Administration

  6. Designing a Backup Strategy (continued) • Determining value of data • Spend more to protect integrity of expensive data • Opportunity cost • Determine when to back up data • Data changes frequently in most organizations • User data • Log files • E-mail archives • Constitutes daily work of users within organization The Complete Guide to Linux System Administration

  7. A Linux Backup Strategy • Backup level • Defines how much data is backed up • Backup operation at given backup level stores all data that has changed since last backup of previous level • Levels • Level 0, full backup • Level 1, weekly differential backup • Level 2, daily differential backup The Complete Guide to Linux System Administration

  8. A Linux Backup Strategy (continued) • Full backup • Also called epoch backup • Everything on system is backed up • Differential backup stores only files that changed since full backup • Incremental backup stores files that changed since most recent incremental backup or differential backup The Complete Guide to Linux System Administration

  9. A Linux Backup Strategy (continued) The Complete Guide to Linux System Administration

  10. A Linux Backup Strategy (continued) • Restoring file from three-level backup • Check most recent level 2 backup, level 1backup, and level 0 backup • Entire system restore from three-level backup • Restore most recent level 0 backup, level 1 backup, and level 2 backup The Complete Guide to Linux System Administration

  11. A Linux Backup Strategy (continued) • Managing and storing backup media • Determine how many backup media needed for each level • Carefully label media • Most organizations store one set of monthly backup media off-site • Possibly weekly as well • Can reuse same set of level 1 weekly tape cartridges each month starting with oldest one The Complete Guide to Linux System Administration

  12. A Linux Backup Strategy (continued) The Complete Guide to Linux System Administration

  13. A Linux Backup Strategy (continued) • Backing up root file system • Requires special attention in backup plan • Contains tools normally used to restore damaged data • Think about how to respond if root file system is damaged The Complete Guide to Linux System Administration

  14. Hardware and Software Issues • Determine best tools to get job done • Linux includes all necessary software utilities for many backup tasks • Backup media such as tape cartridges cost much less than hard disk • Verify backups regularly • Check backup log each morning The Complete Guide to Linux System Administration

  15. Hardware and Software Issues (continued) • Know exactly what information is backed up • Backup utilities normally include options to maintain or ignore file ownership and permissions • Choose whether to use compression feature • When data compressed, redundancy removed The Complete Guide to Linux System Administration

  16. Using Linux Backup Utilities • tar • cpio • dump • restore • dd (“Data dump”) The Complete Guide to Linux System Administration

  17. Using Linux Backup Utilities (continued) • Graphical utilities rely on tar, cpio, or dump and restore in background • Common to use Linux backup utilities across network • Most full-featured backup utilities create own network connections • ark • Graphical tool for managing data backup operations The Complete Guide to Linux System Administration

  18. Using Linux Backup Utilities (continued) • Specialized software for maintaining large numbers of backup media for large volumes of data • BRU (backup and restore utility) • Arkeia • Storix • Hypertape • Amanda • Legato The Complete Guide to Linux System Administration

  19. Understanding Redundant Disk Systems and RAID • Redundant arrays of inexpensive disks • Called RAID subsystems or RAID arrays • Group or array of inexpensive hard disks • If one disk fails, others can take over until failed disk replaced • Can be implemented by Linux kernel • As device called /dev/md0 • Composed of several actual hard disk partitions The Complete Guide to Linux System Administration

  20. Understanding Redundant Disk Systems and RAID (continued) • Defining RAID levels • Levels differ in: • Amount of fault tolerance provided • Speed of reading or writing data • Cost of implementation • RAID-Linear • Combine multiple physical devices into single logical device • Not truly RAID level The Complete Guide to Linux System Administration

  21. Understanding Redundant Disk Systems and RAID (continued) • RAID-0 • Data storage technique called striping • Single block of data divided into pieces • Stored on more than one hard disk • RAID-1 • Mirrors data across multiple hard disks • RAID-3 • Stripes data across multiple hard disks • Provides additional protection against failure by using parity The Complete Guide to Linux System Administration

  22. Understanding Redundant Disk Systems and RAID (continued) The Complete Guide to Linux System Administration

  23. Understanding Redundant Disk Systems and RAID (continued) • Mirroring • Two or more hard disks contain identical information • Duplexing • Mirrored hard disks on separate controller cards • Parity • Technique that allows corrupted data to be reconstructed using extra information created as data stored The Complete Guide to Linux System Administration

  24. Understanding Redundant Disk Systems and RAID (continued) • RAID-5 • Similar to RAID-3 • Parity information and stored data striped across multiple hard disks • Write caching stores information in memory until it can be written to multiple hard disks without degrading performance overall The Complete Guide to Linux System Administration

  25. Understanding Redundant Disk Systems and RAID (continued) The Complete Guide to Linux System Administration

  26. Understanding Redundant Disk Systems and RAID (continued) The Complete Guide to Linux System Administration

  27. Understanding Redundant Disk Systems and RAID (continued) • Hardware-based RAID • Control and management of disk array depends on separate hardware system • All special technology contained in RAID device • Often allow hot-swapping disks • Main disadvantage: cost The Complete Guide to Linux System Administration

  28. Understanding Logical Volume Management • Logical volume manager (LVM) used to manage large hard disks • Physical volumes • Use Disk Druid to set up “real” partitions on multiple hard disks • Grouped together into logical volume group • Treated as regular hard disk • Boot loader not able to work directly with LVM The Complete Guide to Linux System Administration

  29. System Logs • Log files • Detailed records of events within system • Created by many programs • /var/log/messages • Many different programs write messages • Message • Description of what is happening within program • Uses standard format • whatis command • Looks at database of program descriptions • Prints one-line description of program The Complete Guide to Linux System Administration

  30. The syslogd and klogd Daemons • syslogd • System logging daemon • Watches for messages submitted by programs • klogd • Kernel log daemon • Watches for messages submitted by kernel • Logs kernel messages to /var/log/messages The Complete Guide to Linux System Administration

  31. syslogd and klogd Work Together to Process Log Messages The Complete Guide to Linux System Administration

  32. Configuring the System Log • /etc/syslog.conf • Configure syslogd and klogd • Each line in syslog.conf file contains two parts: • Selector • Action The Complete Guide to Linux System Administration

  33. Configuring the System Log (continued) The Complete Guide to Linux System Administration

  34. Configuration File Syntax • Comment lines • Begin with # character • Precede and explain purpose of each line • Some aspects of configuration file syntax not obvious even after reading about facilities and actions • After changing syslog.conf configuration file, service syslog restart The Complete Guide to Linux System Administration

  35. Configuration File Syntax (continued) • SIGHUP signal • Send with kill command • Tells daemon to reread configuration files • kill -HUP ‘cat /var/run/syslogd.pid’ The Complete Guide to Linux System Administration

  36. Using the Logger Utility • Logger utility sends message to syslog function • Example: logger compression utility started • Logged wherever syslog.conf file has configured messages matching selector The Complete Guide to Linux System Administration

  37. Analyzing Log Files • System administrator should regularly check log files for indications of trouble • Become accustomed to what is normal and what is unexpected • Use standard Linux tools to search for information in log files • Use special log management utilities that watch log files for specified conditions • Notify via e-mail about problems The Complete Guide to Linux System Administration

  38. Rotating Log Files • Erase old log files to free up disk space for new log information • Compress log files and store them on archive medium • Rename and compress log files • Common log rotation system stores log files for a month • logrotate utility The Complete Guide to Linux System Administration

  39. Exploring Kernel Components • Learn how Linux keeps track of time • Learn about /proc file system • Work with kernel modules and several high-end features of Linux kernel The Complete Guide to Linux System Administration

  40. Timekeeping in Linux • Hardware clock • Electronic clock with small battery • Maintains correct time even when computer is off • System clock • Internal clock in kernel • Maintained internally as single number • Number of seconds since January 1, 1970 The Complete Guide to Linux System Administration

  41. Timekeeping in Linux (continued) • date command • See current date and time from system clock • hwclock command • See current date and time from hardware clock • Network time server • Computer that maintains highly accurate time based on atomic or radio clocks • Network Time Protocol (NTP) • /etc/ntp.conf file The Complete Guide to Linux System Administration

  42. Kernel Management Using the /proc File System • /proc file system • Interact with system resources as if they were files • Query to learn about system hardware • Can also write information to some file names in /proc • sysctl command • Preferred method of viewing and updating many kernel parameters • Operates on values stored in /proc/sys The Complete Guide to Linux System Administration

  43. Using Kernel Modules • Linux kernel modules • Files containing computer code • Can be loaded into kernel or removed from kernel as needed • lsmod command lists modules that are installed • modinfo command • Learn about modules The Complete Guide to Linux System Administration

  44. Using Kernel Modules (continued) • Adding and removing modules • modprobe command loads module with any required supporting modules • rmmod command removes module from kernel • Module parameters provides information needed by module to locate system resources The Complete Guide to Linux System Administration

  45. Configuring and Upgrading Kernel Components • Add features to kernel by inserting kernel modules • Some kernel features not available as modules • Recompile Linux kernel from source code • File vmlinuz-26.5-1.358 contains Linux kernel • Usually located in / or /boot directory The Complete Guide to Linux System Administration

  46. Installing Kernel Source Code • Source code in single rpm • Named kernel-source • Use rpm command to install • Explore source code files in directory /usr/src/linux-26.5-1.358 • Patch file • Patch command • Insert and change lines based on patch file The Complete Guide to Linux System Administration

  47. Configuring Kernel Features • Select which kernel options to include or activate for system • Configuration utilities • config • menuconfig • xconfig • make command • Programming utility uses instructions in configuration file to execute series of instructions The Complete Guide to Linux System Administration

  48. Compiling a New Kernel • Execute series of make commands • Prepare all source code files • Compile them into kernel image • Requires between 30 minutes and 3 hours • Example: make dep; make bzimage; make modules; make modules_install The Complete Guide to Linux System Administration

  49. Summary • Backup plan creates orderly system for backing up data on regular basis and restoring lost data as needed • Log files record activities of Linux programs • System clock in Linux kernel maintains time and date for system events • RAID systems improve speed and fault tolerance The Complete Guide to Linux System Administration

  50. Summary (continued) • /proc file system • View details about • Kernel • Running processes • Other system information • Linux kernel sometimes updated by Linux vendors via new rpm file The Complete Guide to Linux System Administration

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