Lesson #10 File Systems

Learner Outcomes

• Create new filesystems
• Mount, unmount, check and repair file systems.
• Monitor file system usage and recover from disk full problems
• Establish hard and soft quotas for users.

Activities

• Quiz 3
• Use system tools to find large directories and files that are filling a file system, (sparse files).
• Anatomy of a file system - worksheet
• Create a /home file system.
• View and alter the information in a file system superblock.
• Exercise - Adding File Systems
  1. Create a logical partition of 500 MB: /dev/hda6
  2. Format the partition as ext2
  3. Use tune2fs to add/change the following features:
     1. A label of /home
     2. A journal
     3. Reserved space of 3%
  4. Mount the file system and move all the files from /home to this file system.
  5. Edit /etc/fstab to mount this file system at boot time to /home as an ext3 file system.
  6. Test your configuration by executing the command:
     mount -a
• Exercise - Setting up disk quotas
  1. Enable group quotas for the /home file system by adding grpquota to the options section of /etc/fstab
  2. Remount the /home/file system.
  3. Create the quota files using:
     quotacheck -cgv /dev/hda6
  4. Turn quotas on with:
     quotaon -g /dev/hda6
  5. Set the cis191 and your group's group quotas for inodes and disk blocks using either edquota or setquota.
• Recover from corrupted superblock
• Restore a deleted file
• Demonstrate automounting file systems: CCC Confer Video

Assignment

• Do Lab 7 in the CTC or Networking Lab in 2504
• Read sections 1,3,4,5 and 6 in chapter 9 on Backups, paying special attention to sections 1,3 and 4.

File Systems

1. File System Structure
   • General Terminology
     • Storage
     • File
     • Partition
     • File system
   • Functions of a File System
     • File name translation
     • File protection
     • Data movement
     • Map traversal (Integrity)
2. Development of the ext2 File System
   • UNIX File System (UFS)
     • Bootstrap block
     • Superblock
     • Index nodes (inode table)
     • Allocated blocks
     • Free blocks
   • The Fast File System (FFS)
     • Intended to overcome file fragment problems
   • ext2 takes some features of FFS and UFS
   • Putting it all together
3. ext2 in Depth
   • Linux File System Structure
     • The superblock
     • Primary inodes and their functions
     • Inode space versus the number of actual files
     • ext2 block group trade-off
   • Advanced Features
   • The Future of ext2
4. Consistency Checking
   • Automating Consistency Checks
     • Searches for and locates all disk blocks
     • inodes refer to unique data blocks
     • Consistency Checking takes time
     • Forced only when dirty volume mount is attempted
     • Why not simply push power button to shut down?
     • Assessed after so many mount operations or amount of time
5. Fragmentation
   • FFS, ext2 File Systems limit this with cylinder, Block Groups
   • ext2 File Systems Tend to have little file fragmentation
   • Largest Contiguous ext2 File limited by Group Block Size
   • Defragmenting an ext2 File System
     • Usually not enough fragmentation to use defragmentation in ext2
     • May be bugs in defragmenter
6. Other File Systems
   • ReiserFS
   • XFS
   • ext3
   • JFS
7. File System Hierarchy Standard
   • / subdirectories

     bin	boot	dev	etc	home
     lib	mnt	opt	proc	root
     sbin	tmp	usr	var

   • Program File Placement
   • Mounting a Volume
8. File System Configuration Files
   • /etc/fstab
     • Six fields per record
     • Specifies where and how file systems are mounted
   • /etc/mtab
   • Volume Mounting and Unmounting
     • File System must be mounted for files to be accessed
     • Specify device name and mount point to mount an unlisted device
9. File System Maintenance
   • Built-In Fixes to Common Problems
     • Sudden loss of power in power failure
     • User switching off power improperly
     • Crash due to kernel or software
     • Program working on many files crashes
   • Corrupted File System Characteristics
     • Many files using one data block
     • Data blocks marked as free but being used (and vice-versa)
10. The e2fsprogs suite
    • Understanding Front-End Programs
      • Several files in e2fsprogs are front-end
      • Makes use of back-end programs easier
      • Saves room and typing
11. File Protperties
    • chattr

      -R	-V	-A	-c
      -d	-S	-s	-u

      lsattr
      • Lists the ext2 file system's extended permissions
12. File System Creation
    • mkfs.ext2 (mke2fs)
      • Creates Linux ext2 file systems
    • mklost+found
      • Creates lost and found directory on mounted ext2 file systems
    • resize2fs
      • Resize an ext2 file system
    • e2label
      • Used to change or view label of ext2 file system
13. File System Check
    • fsck.ext2 (e2fsck)
      • Used to check a Linux ext2 file system for errors
      • Invokes file system checker
    • fsck
      • Used to check or repair file systems
      • 0 or empty field,1, 2
    • badblocks
      • Searches block devices for bad blocks
14. File System Manipulation
    • debugfs/dumpe2fs
      • File system debugger
      • Most dangerous and powerful of e2fsprogs
    • tune2fs
      • Adjusts file system parameters
    • uuidgen
      • Creates universally unique identities

Relevant Commands and Files