File System

Question 1

Types of Data?

Answer 1

Numeric
Character
Binary

Question 2

File Attributes?

Answer 2

Name
Identifier
Type
Location
Size
Protection
Time, date

Question 3

File Operations?

Answer 3

Create
Write
Read
Reposition - Seek
Delete
Truncate
Open
Close

Question 4

Open Files?

Answer 4

Open-file table: tracks open files.
File Pointer: Pointer to last read/write location, per process that has the file open.
File-open count: counter of number of times a file is open, to allow removal of data from open-file table.

Question 5

Open File Locking?

Answer 5

Similar to reader-writer locks
Shared lock similar to reader lock - several processes can acquire concurrently.
Exclusive lock similar to writer lock

Question 6

Mandatory?

Answer 6

Access is denied depending on locks held and requested

Question 7

Advisory?

Answer 7

Processes can find status of locks and decide what to do

Question 8

File Structure?

Answer 8

None
Simple Record Structure
Compex Structures

Question 9

Access Methods?

Answer 9

Sequential Access

Direct Access

Question 10

Sequential Access

Answer 10

Read next
Write next
reset

Question 11

Direct Access?

Answer 11

File is fixed length logical records.
Read n
write n
position to n
--read next
--write next
rewrite n

Question 12

Disk structure?

Answer 12

Disk can be subdivided into partitions

Disk can be RAID protected against failure

Question 13

Operations Performed on Directory?

Answer 13

Search for a file
Create a file
Delete a file
List a directory
Rename a file
Traverse a file system

Question 14

The directory is organized logically to obtain?

Answer 14

Efficiency
Naming
Grouping

Question 15

Acyclic-Graph Directories

Answer 15

Two different names

If dict deletes list -> dangling pointer.

Question 16

Solution to dangling pointer?

Answer 16

Backpointers, so we can delete all pointers variable size records a problem.
Backpointers using a daisy chain organization
Entry-hold-count solution

Question 17

New directory entry types?

Answer 17

Link - another name

Resolve the link - follow pointer to locate the file

Question 18

File Sharing?

Answer 18

Sharing of files on multi-user systems is desirable

Sharing may be done through a protection scheme

Question 19

If multi-user system?

Answer 19

User IDs identify users, allowing permissions and protections to be per-user.

Group IDs allow users to be in groups, permitting group acscess rights

Question 20

Types of File Sharing?

Answer 20

Manually via FTP
Automatically via DFS
Semi-Automatically via WWW

Question 21

Client-Server?

Answer 21

Model allows clients to mount remote file systems from servers.

Server can serve multiple clients
Client and user-on-client identification is insecure or complicated.

Question 22

Client-Server types?

Answer 22

NFS

CIFS

Question 23

NFS?

Answer 23

Is standard UNIX client-server file sharing protocol

Question 24

CIFS?

Answer 24

is standard windows protocol

Question 25

Failure Modes?

Answer 25

All file systems have failure modes

Non user data is called metadata

Question 26

Consistency Semantics?

Answer 26

how multiple users are to access a shared file

Similar to process synchronization algorithms

Question 27

Types of Semantics?

Answer 27

AFS

UFS

Question 28

AFS?

Answer 28

Andrew File System implemented complex remote file sharing semantics

Question 29

UFS?

Answer 29

Unix File System implements
Writes to an open file visible immediately to other users of the same open file

Sharing File pointer to allow multiple users to read and write concurrently.

Question 30

Protection?

Answer 30

The owner manages:
Actions
Permissions

Question 31

Types of access?

Answer 31

Read
Write
Execute
Append
Delete
List

Question 32

Modes of Access?

Answer 32

Read
Write
Execute