Files and Directories

Question 1

Secondary Storage Systems include _______ disks, ____, and tapes

Answer 1

magnetic, SSDs

Question 2

Storing bits on ______ is different from storing them on flash

Answer 2

disk

Question 3

The OS provides a ______ view of storage to users

Answer 3

uniform

Question 4

The OS creates file _______ on storage media

Answer 4

systems

Question 5

File systems ________ store and retrieve data

Answer 5

efficiently

Question 6

File systems enable ______ view of data via files and __________

Answer 6

logical, directories

Question 7

A file is a linear array of _____

Answer 7

bytes

Question 8

Files persistently record user-defined information on ________

Answer 8

storage

Question 9

What is the inode number?

Answer 9

The low-level name that internally identifies a file

Question 10

What are example of operation on files?

Answer 10

• Open
• Close
• Read
• Write
• Reposition
• Delete
• Truncate

Question 11

More complex operations on files can be made using ________ operations

Answer 11

primitive

Question 12

In the POSIX file interface, what function do you use to create/open a file?

Answer 12

open(name, arg)

Question 13

In the POSIX file interface, what does open() return?

Answer 13

A file descriptor used for accessing files

Question 14

In the POSIX file interface, what do the arguments O_CREAT, O_WRONLY. and O_TRUNC do in open()?

Answer 14

O_CREAT - create new file
O_WRONLY - only write to the file
O_TRUNC - remove any existing content in the file

Question 15

In the POSIX file interface, how do you close a file?

Answer 15

close(file descriptor)

Question 16

In the POSIX file interface, how do you rename a file?

Answer 16

rename(char *old, char *new)

Question 17

In the POSIX file interface, how do you delete a file?

Answer 17

unlink(char *name)

Question 18

In the POSIX file interface, how do you read files?

Answer 18

read(file descriptor, buffer pointer, the size of the buffer)

Question 19

In the POSIX file interface, how do you write to files?

Answer 19

write(file descriptor, buffer pointer, the size of the buffer)

Question 20

In the POSIX file interface, what does read() return?

Answer 20

Number of bytes read

Question 21

In the POSIX file interface, what does write() return?

Answer 21

Number of bytes written

Question 22

In the POSIX file interface, you should repeat multiple _______ calls for larger files

Answer 22

write()

Question 23

In the POSIX file interface, each open file has a _______ offset

Answer 23

current

Question 24

In the POSIX file interface, the current offset determines _____ the next read or write will begin from the file

Answer 24

where

Question 25

Current offset is also known as the ____ offset into the file

Answer 25

byte

Question 26

In the POSIX file interface, read()/write() advances the current offset by the number of bytes _______/______

Answer 26

read/written

Question 27

In the POSIX file interface, we can explicitly update the current offset using ______

Answer 27

lseek()

Question 28

``` In the POSIX file interface, for the function off_t lseek(int fd, off_t offset, int whence); what do the 4 parts of the function do? ```

Answer 28

off_t: returns the resulting current offset fd: file descriptor offset: target position whence: how the seek is performed

Question 29

In the POSIX file interface, for the function lseed(). what are the 3 valid whence values and what do they do?

Answer 29

- SEEK_SET: current offset = [offset] - SEEK_CUR: current offset += [offset] - SEEK_END: current offset = size of the file plus [offset] bytes

Question 30

Storage and file systems ______ data

Answer 30

buffer

Question 31

File system buffer data to improve __________

Answer 31

performance

Question 32

In file systems, data written and read are __________ in memory

Answer 32

buffered

Question 33

In file systems, data only _______ gets written from buffer to storage. We can ______ written data.

Answer 33

periodically, lose

Question 34

The solution to losing data in the buffer is _______

Answer 34

fsync(int fd)

Question 35

fsync() forces all ______ data to disk for the referred file

Answer 35

dirty

Question 36

What is dirty data?

Answer 36

Data not yet written to disk

Question 37

What does stat()/fstat() do?

Answer 37

Show the file metadata

Question 38

Metadata refers to ___________ about data

Answer 38

information

Question 39

Directories are logical _________ of files/directories

Answer 39

groupings

Question 40

Directories also have an _____ number

Answer 40

inode

Question 41

Directories list pairs of {user-readable ____, _____ number}

Answer 41

name, inode

Question 42

What are some operations of directories?

Answer 42

- search for file - create file - delete file - rename file - list directory - traverse the file system

Question 43

In the POSIX directory interface, how do you make a directory?

Answer 43

mkdir()

Question 44

What 2 entries to empty directories have?

Answer 44

- .(itself) | - ..(parent)

Question 45

In the POSIX directory interface, what does struct_dirent store?

Answer 45

Information about the directory

Question 46

In the POSIX directory interface, we use _______ to delete a directory

Answer 46

rmdir()

Question 47

When using rmdir(), we have to make sure that the directory is ______

Answer 47

empty

Question 48

In the POSIX directory interface, what is the function for linking a new file name to an old one?

Answer 48

link(old pathname, new)

Question 49

link() allows us to create another way to ______ to the same file

Answer 49

refer

Question 50

In the POSIX directory interface, how is link implemented internally? (2 steps)

Answer 50

1. Create another name in the directory | 2. Refer it to the same inode number of the original file

Question 51

In a ____ link, there is no difference between the new and old file

Answer 51

hard

Question 52

A _______ _____ tracks how many different names have been linked to an inode

Answer 52

reference count

Question 53

When unlink() is called, the reference count _________

Answer 53

decrements

Question 54

A file is _____ deleted when the reference count reaches zero

Answer 54

truly

Question 55

How can you find the reference count of a file?

Answer 55

stat()

Question 56

Symlinks are more _______ than hard links

Answer 56

useful

Question 57

Hard links cannot create to a _________ or to a file to another ___________

Answer 57

directory, partition

Question 58

Inode numbers are only unique within a file ______

Answer 58

system

Question 59

Symlinks are a _______ type the file system knows about

Answer 59

third

Question 60

The symlink is a _____ by itself

Answer 60

file

Question 61

The symlink holds the ____________ of the linked-to file as the data of the link file

Answer 61

pathname

Question 62

In a symlink, a longer pathname makes a bigger ________ file

Answer 62

symlink

Question 63

What is a dangling reference?

Answer 63

When the original file is removed and the symlink points to an invalid file

Question 64

How do you create a file system?

Answer 64

mkfs()

Question 65

mkfs() initializes an ______ file system, starting with a ______ __________ onto a disk partition

Answer 65

empty, root directory

Question 66

mkfs() has two inputs: ________ and _____ ______- type

Answer 66

device, file system

Question 67

_______ takes an existing directory as a target mount point

Answer 67

mount()

Question 68

mount() _____ a new file system onto the directory tree at the mount point. The original files are ________ until ________

Answer 68

pastes, invisible, unmounted

Question 69

A mount ______ shows what is mounted on a system

Answer 69

program

Question 70

For mounting, ext4 refers to a ______ disk-based file system

Answer 70

standard

Question 71

For mounting, ______ is a file system for accessing information about the current processes

Answer 71

proc

Question 72

For mounting, ______ is a file system for temporary files

Answer 72

tmpfs

Question 73

For mounting, AFS is a _________ file system

Answer 73

distributed