3 - Filing Systems

Question 1

Three Filing System types

Answer 1

Single-Level: all files in one
Two Level: Each user has directory
Multi : any node may be file or directory

Question 2

Define a hard disk block

Answer 2

A sector traditionally capable of 25616-bit words or 5128-bit bytes (22^9 bytes)

Modern disks allow up to 4KiB but these are in 512 byter blocks (this course)

Question 3

Boot Block

Answer 3

Contains the bootstrap program

Question 4

Super Block

Answer 4

Contains data defining the file system

• Num of inode blocks
• size
• free block details
• free inode details
• last sync date

Question 5

Inode

Answer 5

Contains information about nodes where a node is a file or directory etc

Question 6

What is the structure of an inode?

Answer 6

Flags (2 bytes)
Link Count (1)
Owner ID (1)
Group ID (1)
File Size (3 bytes)
Access dates/times (8 bytes)
8 address words (16bytes)

adds to 32 bytes

Question 7

If each inode is 32 bytes and each block is 512 bytes in size then each block can store…

Answer 7

512/32 = 2&9/2^5 = 2^4 = 16 inodes

Question 8

What is the size of huge file limited to?

Answer 8

2^24 bytes as there are only 24bits set aside in the inode for file size in Unix ver 6

Question 9

Directory Entry

Answer 9

Made up of 16 bytes (2 for inode num and 14 for file name) and stored with 31 other directory entries in a single disk block

Question 10

Are filenames stored in inode?

Answer 10

No, they are stored in a block on the hard disk with the corresponding inode that defines that directory

Question 11

What are the three permissions?

Answer 11

r -read
w - write
x - execute

Question 12

What is the permission order (in terms of the 3 segments of rwx)?

Answer 12

owner-group-all