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Linux+ Guide to Linux Certification, Second Edition

Linux+ Guide to Linux Certification, Second Edition. Chapter 6 Linux Filesystem Administration. Objectives. Identify the structure and types of device files in the /dev directory Understand common filesystem types and their features

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Linux+ Guide to Linux Certification, Second Edition

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  1. Linux+ Guide to Linux Certification, Second Edition Chapter 6 Linux Filesystem Administration

  2. Objectives • Identify the structure and types of device files in the /dev directory • Understand common filesystem types and their features • Mount and unmount floppy disks to and from the Linux directory tree • Mount and unmount CD-ROMs to and from the Linux directory tree • Create hard disk partitions Linux+ Guide to Linux Certification, 2e

  3. Objectives (continued) • Mount and unmount hard disk partitions to and from the Linux directory tree • Monitor free space on mounted filesystems • Check filesystems for errors • Use hard disk quotas to limit user space usage Linux+ Guide to Linux Certification, 2e

  4. The /dev Directory • Device file: File representing a system device • Typically found in /dev directory • Character devices: Transfer data to and from system character by character • Block devices: Transfer chunks or blocks of data using physical memory as a buffer • Fast data transfer • CD-ROM, HDD, floppy disks Linux+ Guide to Linux Certification, 2e

  5. The /dev Directory (continued) Table 6-1: Common device files Linux+ Guide to Linux Certification, 2e

  6. The /dev Directory (continued) Table 6-1 (continued): Common device files Linux+ Guide to Linux Certification, 2e

  7. The /dev Directory (continued) • Major number: Points to the device’s driver in the Linux kernel • Minor number: Indicates the particular device • Device file type (block or character), major number, and minor number make up a device file’s unique characteristics • mknod command: Can be used to re-create a corrupted device file • Must know file type, major, and minor numbers Linux+ Guide to Linux Certification, 2e

  8. Filesystems • Filesystem: Organization imposed on physical storage media • Formatting: Creating a filesystem on a device Linux+ Guide to Linux Certification, 2e

  9. Filesystem Types Table 6-2: Common Linux filesystems Linux+ Guide to Linux Certification, 2e

  10. Filesystem Types (continued) Table 6-2 (continued): Common Linux filesystems Linux+ Guide to Linux Certification, 2e

  11. Mounting • Mounting: Making a device accessible to users via the logical directory tree • Mount point: Directory to which a device is attached • Any existing directory can be a mount point • Root filesystem: When Linux filesystem first turned on, a filesystem on the hard drive is mounted to the / directory • Contains most OS files Linux+ Guide to Linux Certification, 2e

  12. Mounting (continued) Figure 6-1: The directory structure prior to mounting Linux+ Guide to Linux Certification, 2e

  13. Mounting (continued) Figure 6-2: The directory structure after mounting a floppy device Linux+ Guide to Linux Certification, 2e

  14. Mounting (continued) • mount command: Used to mount devices to mount point directories • With no options or arguments, lists currently mounted filesystems • umount command: Used to unmount devices from mount point directories Linux+ Guide to Linux Certification, 2e

  15. Working with Floppy Disks • Floppy disks must be prepared before use • Formatted with a filesystem • mkfs (make filesystem) command: Used to format a disk device with a filesystem • –t option: Specifies filesystem type • Default is ext2 filesystem • To mount or unmount floppies, must ensure that no user is currently using the mount point directory • fuser command: With the –u option, lists users using a directory Linux+ Guide to Linux Certification, 2e

  16. Working with Floppy Disks (continued) Table 6-3: Commands used to create filesystems Linux+ Guide to Linux Certification, 2e

  17. Working with Floppy Disks (continued) • /etc/fstab file: Used to mount devices at boot time • Also consulted when users do not specify enough mount command arguments • Six fields: Device to mount, mount point, type, mount options, dump#, fsck# Linux+ Guide to Linux Certification, 2e

  18. Working with Floppy Disks (continued) Table 6-4: Useful commands when mounting and unmounting filesystems Linux+ Guide to Linux Certification, 2e

  19. Working with Floppy Disks (continued) Figure 6-3: Mounting a floppy device using a GUI environment Linux+ Guide to Linux Certification, 2e

  20. Working with Floppy Disks (continued) Figure 6-4: Accessing filesystem devices in the KDE desktop Linux+ Guide to Linux Certification, 2e

  21. Working with CD-ROMs • Most Linux systems have ATAPI-compliant IDE CD-ROM drive • Acts as a normal IDE hard disk • Must configure in one of the following: • Primary master (/dev/hda) • Primary slave (/dev/hdb) • Secondary master (/dev/hdc) • Secondary slave (/dev/hdd) Linux+ Guide to Linux Certification, 2e

  22. Working with CD-ROMs (continued) • Typically use iso9660 filesystem type and are not writable • Mount with –r (read-only) option • Cannot be ejected until properly unmounted Linux+ Guide to Linux Certification, 2e

  23. Working with Hard Disks • IDE HDDs must be configured in one of the following: • Primary master (/dev/hda) • Primary slave (/dev/hdb) • Secondary master (/dev/hdc) • Secondary slave (/dev/hdd) • Different device file for each Linux+ Guide to Linux Certification, 2e

  24. Working with Hard Disks (continued) • SCSI hard disks well-suited to Linux servers • Faster access speed • Multiple hard drives can be attached to a controller • Associated with different device files • First SCSI HDD (/dev/sda) • Second SCSI HDD (/dev/sdb) • Third SCSI HDD (/dev/sdc) • And so on Linux+ Guide to Linux Certification, 2e

  25. Hard Disk Partitioning • As disk size increases, organization becomes more difficult and chance of error increases • Partition: A physical division of an HDD; can have own filesystem • Good practice to use more than two partitions • Segregate different types of data • Allow for use of multiple filesystem types on one HDD • Reduce chance that filesystem corruption will render a system unusable • Speeds up access to stored data; keep filesystems small Linux+ Guide to Linux Certification, 2e

  26. Hard Disk Partitioning (continued) • Track: Areas on a hard disk that form a concentric circle of sectors • Sector: Smallest unit of data storage on a hard disk • Block: Combination of sectors; commonly used by filesystem commands • Cylinder: Series consisting of the same concentric track on all of the metal platters inside a HDD • Partition definitions stored in first readable sector of the hard disk • Master Boot Record (MBR) or master boot block (MBB) Linux+ Guide to Linux Certification, 2e

  27. Hard Disk Partitioning (continued) Figure 6-5: The physical areas of a hard disk Linux+ Guide to Linux Certification, 2e

  28. Hard Disk Partitioning (continued) Table 6-5: Common hard disk partition device files for /dev/hda and /dev/sda Linux+ Guide to Linux Certification, 2e

  29. Hard Disk Partitioning (continued) Table 6-5 (continued): Common hard disk partition device files for /dev/hda and /dev/sda Linux+ Guide to Linux Certification, 2e

  30. Hard Disk Partitioning (continued) Figure 6-6: A sample Linux partitioning strategy Linux+ Guide to Linux Certification, 2e

  31. Hard Disk Partitioning (continued) Figure 6-7: A sample dual-boot Linux partitioning strategy Linux+ Guide to Linux Certification, 2e

  32. Working with Hard Disk Partitions • fdisk command: Create partitions after installation • Specify hard disk partition as an argument • tune2fs command: Create a journal file on the filesystem • Convert ext2 to ext3 • Edit /etc/fstab file to allow system to mount new filesystems automatically at boot time Linux+ Guide to Linux Certification, 2e

  33. Monitoring Filesystems • Check mounted filesystems periodically • Errors • Disk Space usage • Inode usage Linux+ Guide to Linux Certification, 2e

  34. Disk Usage • Using more filesystems typically results in less hard disk space per filesystem • Errors when filesystems fill up with data • e.g., free space on / filesystem falls below 10% • df (disk free space) command: Monitor free space used by mounted filesystems • –h option: More user friendly Linux+ Guide to Linux Certification, 2e

  35. Disk Usage (continued) • du (directory usage) command: View size of a directory and contents in Kilobytes • –s option: Summarizes output • dumpe2fs command: View total number of inodes and free inodes for ext2 or ext3 filesystem • Use –h option Linux+ Guide to Linux Certification, 2e

  36. Checking Filesystems for Errors • Filesystem corruption: Errors in filesystem structure preventing retrieval of data • Commonly occurs due to improper system shutdown • Syncing: Process of writing data stored in RAM to the HDD • Bad blocks: Unusable areas of a disk • Cannot hold a magnetic charge Linux+ Guide to Linux Certification, 2e

  37. Checking Filesystems for Errors (continued) • fsck (filesystem check) command: Check a filesystem for errors • Filesystem must be unmounted • –f option used to perform full check • e2fsck command: Check ext2 and ext3 filesystems • Reiserfsck: Check reiserfs filesystems Linux+ Guide to Linux Certification, 2e

  38. Checking Filesystems for Errors (continued) Table 6-6: Common options to the fsck command Linux+ Guide to Linux Certification, 2e

  39. Hard Disk Quotas • If several users on a system, must be enough hard disk space for each user’s files • Hard disk quotas: User limits on filesystem usage • Restrict number of files/directories or total disk space usage • Soft limit: User may exceed quota briefly • Hard limit: Limit cannot be exceeded Linux+ Guide to Linux Certification, 2e

  40. Hard Disk Quotas (continued) • quotaon and quotaoff commands: Toggle quotas on and off • edquota command: Edit user quotas • repquota command: Report user quotas • quota command: Allows regular users to view quotas and current usage Linux+ Guide to Linux Certification, 2e

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