Linux Lab (AD-506) - Unit 3 Short Notes

How unit 3 is examined

This unit covers file system types and the UFS on-disk structures (boot block, super block, inode), plus tuning and repair; no past questions have been asked on it recently.

Definition of File System, Defining Geometry, Disk Controller, Solaris File System, Disk Based File Systems, Network-Based File Systems, Virtual File systems, UFS File System

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Definition. <mark>A file system is the method and data structure an operating system uses to name, store, organise and retrieve files on a storage device.</mark>

Key points.

1. Disk geometry is the physical layout of a disk into platters, cylinders, tracks and sectors; the disk controller drives the hardware and reads or writes these sectors.
2. Disk-based file systems (UFS, ext) live on local disks, network-based file systems (NFS) share files from a remote host, and virtual file systems (VFS, procfs, tmpfs) exist in memory.
3. Solaris uses UFS, a disk-based file system divided into cylinder groups, each holding a super block copy, inodes and data blocks.

The Boot Block, The Super Block, The Inode, Tuning File System, Repairing File System

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Definition. <mark>The boot block holds the program that loads the OS, the super block describes the whole file system, and an inode stores every attribute of one file except its name.</mark>

Key points.

1. The boot block is the first block of the file system and holds the bootstrap loader.
2. The super block records the file system size, block size, free block and inode counts, and is copied in each cylinder group.
3. An inode holds owner, permissions, size, timestamps, link count and the pointers to the data blocks.
4. Tuning uses tunefs to change parameters such as minimum free space and optimisation preference (time or space).
5. Repairing uses fsck on an unmounted file system to check and fix inconsistencies in blocks, inodes and links.

Last-minute revision

• A file system organises files on a storage device.
• Disk geometry: platters, cylinders, tracks, sectors.
• The disk controller reads and writes sectors on the disk.
• UFS is the Solaris disk-based file system.
• NFS is a network-based file system; VFS is the virtual layer over all file systems.
• The boot block holds the bootstrap loader.
• The super block describes the file system and is replicated per cylinder group.
• An inode stores file attributes and block pointers, not the file name.
• tunefs tunes a file system; fsck repairs it.
• Run fsck only on an unmounted file system.

Memory hooks

• Boot, Super, Inode: "Start, Summary, Single file".
• tunefs tunes, fsck fixes.
• Inode has everything except the name; the directory holds the name.

Coverage checklist

• Definition of File System, Defining Geometry, Disk Controller, Solaris File System, Disk Based File Systems, Network-Based File Systems, Virtual File systems, UFS File System: no past questions.
• The Boot Block, The Super Block, The Inode, Tuning File System, Repairing File System: no past questions.