CSC 209: midterm solutions, October 2011

2. [6 marks]
Here is a portion of a unix filesystem. Like the "ls -l" output, we list whether the file (inode) is a plain file, directory, etc, with '-' for plain file or 'd' for directory. In the case of directories, the table also states the data content of the directory itself (a list of pairs of: inode number, name).

2	d	. 2, .. 2, usr 7, etc 4, bin 6
3	-
4	d	. 4, .. 2, passwd 3
5	d	. 5, .. 7, fsys.fig 10, src 11
6	d	. 6, .. 2, date 9
7	d	. 7, .. 2, bin 8, ajr 5, you 12
8	d	. 8, .. 7
9	-
10	-
11	d	. 11, .. 5, hello.c 13
12	d	. 12, .. 7, a1 14
13	-
14	-
15
16
17

a) Suppose I do "mkdir /usr/ajr/newdir". Write in all changes/additions to the above list. (There are some free inodes at the end for you to use for new files.)

b) If instead I were cd'd to /usr/ajr and typed simply "mkdir newdir". would the result differ, and if so, how?

c) Suppose I do "ln -s /usr/you/a1 /usr/ajr/othera1", creating a "symbolic link". Write in all changes/additions to the above list.

d) If instead I were cd'd to /usr/you and typed "ln -s a1 /usr/ajr/othera1", would the result differ, and if so, how?

Solutions:

2a)

add to inode 5: ", newdir 15"
inode 15 is a directory ('d')
inode 15's contents: ". 15, .. 5"

2b) no difference

2c)

add to inode 5: ", othera1 16"
inode 16 is a symlink ('l')
inode 16's contents (not required in grading): "/usr/you/a1"

2d) inode 16's contents would be "a1". So it wouldn't work (because it would be relative to /usr/ajr).

[sample midterm from Fall 2011]