answers to lab 3

Q: 1. Create a file called "exercise03answers.txt" A: e.g.

touch exercise03answers.txt

vi exercise03answers.txt

Q: 2. At the top of the file, use the label as defined before. A: as before

Q: 3. Put on a line the word "lab" by itself, then work on lab exercises 1-5 below. List all the relevant commands and arguments that you had to use in the lab exercises. Put in comments to show why you did something (this can help your mark even if you did something wrong). A: in sequence

In my directory on the course linux server (my username is "gj"), is a directory called "public_html/dropbox". In this location, create a directory the name of which is your studentid. Set the permissions on this directory to 700.
```
# go to the directory, so I don't have to type so much
cd ~gj/public_html/dropbox/

# create directory, where my studentid is 01234567890
mkdir 01234567890

# set the permissions as indicated with chmod
chmod 700 01234567890
```

In the directory you have just created, put a copy of lines 7-15 of the password file into a file called "partpasswd".

# go to the directory, so I don't have to type so much later on
cd 01234567890

Different options:

# copy original file
cp /etc/passwd partpasswd
# edit file
vi partpasswd
6dd9j100dd:w
# = delete lines 1 to 6, go 9 lines down, remove 100 lines, write file

# use tools
head -15 /etc/passwd | tail -9
# use cut and paste
vi partpasswd

# use tools and redirection
head -15 /etc/passwd | tail -9 > partpasswd

Change the permissions on "partpasswd" so that everyone can read and write the file, but nothing else.
NOTE: this was an ambiguous question, so both the following answers are correct:

# set permissions so that everyone can read and write the file, but
# they cannot do anything else
chmod 666 partpasswd

# change the permissions so that everyone will get read and write
# access, but leave other permissions alone
chmod a+rw partpasswd

Create a new file called "partgroup". Every line should contain one GID followed by a space, followed by the name of the group. List ONLY the GIDs that appear in "partpasswd". Make sure the list is sorted numerically, and remove duplicates.

# copy partpasswd to a new file
cp partpasswd partsolved
# use vi, and edit
vi partsolved
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j0
6dwwd$j
:w!

# sort and remove duplicates
sort -u partsolved > partgroup

# cross reference the numbers by grepping for them in /etc/group
grep 0 /etc/group
grep 12 /etc/group
etc...

# put the entries in the file with vi
vi partgroup

Remove all write access from "partgroup".

# remove write access from all
chmod a-w partgroup

Q: 4. Put on a line the word "notes" by itself, then answer the questions from the course notes file called "permissions.txt" A: in sequence

---------
Exercises
---------

Given the following inode permissions:

    ---x------    1 dar      staff         123 Apr  1  2003 dar1
    dr---wx-w-    1 dar      dat2330       512 Apr  1  2003 dar2
    -r---wx-w-    1 les      dat2330       123 Apr  1  2003 les1
    drwxrw-r-x    1 les      alumni        512 Apr  1  2003 les2
    -rwxrw-r-x    1 pat      alumni        123 Apr  1  2003 pat1
    d--x------    1 pat      staff         512 Apr  1  2003 pat2
    -rw-r--r--    1 root     system        123 Apr  1  2003 root1
    drwx----wx    1 root     system        512 Apr  1  2003 root2

And these users:

    root - super user
    pat  - in groups "student" and "dat2330"
    les  - in groups "alumni" and "staff"
    dar  - in groups "alumni" and "dat2330"
    kai  - in groups "alumni" and "system"
    tam  - in groups "system" and "staff"
    dod  - in groups "nobody"

Answer these questions:

*)  What type of inode is each file?  (directory, file, other...)

Every name that ends with the number "1" is a file, every name that end with the number "2" is a directory.

*)  What permissions do each of the users have on each file inode?
    - which set of permissions apply to each user?
    - can the user read the file?
    - can the user write the file?
    - can the user execute the file?

	root	pat	les	dar	kai	tam	dod
dar1	rwx	---	---	--x	---	---	---
les1	rw-	-wx	r--	-wx	-w-	-w-	-w-
pat1	rwx	rwx	rw-	rw-	rw-	r-x	r-x
root1	rw-	r--	r--	r--	r--	r--	r--

*)  What permissions do each of the users have on each directory inode?
    - which set of permissions apply to each user?
    - can the user read the directory names?
    - can write the directory (create new names, delete names, rename)?
    - can search (pass through) the directory to the contained inodes?

dar2	rwx	-wx	-w-	r--	-w-	-w-	-w-
les2	rwx	r-x	rwx	rw-	rw-	r-x	r-x
pat2	rwx	--x	---	---	---	---	---
root2	rwx	-wx	-wx	-wx	---	---	-wx

Q: 5. Put on a line the word "book" by itself, then answer questions 1-4 and 6-10 from the book, chapter 4, pages 103-105. A: in sequence

1. absolute pathname, relative pathname or simple filename?
1.a simple filename
1.b relative pathname
1.c absolute pathname
1.d absolute pathname
1.e relative pathname
1.f simple filename
2. make home dir your working dir
```
cd
```
```
cd /home/loginname
```
identify working directory
```
pwd
```
3. /home/alex is working dir, literature is a subdirectory, give three different ways to create a subdirectory classics.
```
mkdir literature/classics
```
```
cd literature; mkdir classics
```
```
mkdir /home/alex/litarature/classics
```

3. remove classics directory

rmdir literature/classics

cd literature; rmdir classics

rmdir /home/alex/literature/classics

rm -r literature/classics

cd literature; rm -r classics

rm -r /home/alex/literature/classics

df -h

Filesystem            Size  Used Avail Use% Mounted on
/dev/hda3             2.7G  2.3G  342M  87% /
/dev/hda1             7.6M  4.4M  2.9M  61% /boot
/dev/hdc1              17G  2.2G   14G  14% /d2

4.a 3
4.b /dev/hda3
4.c

ln: creating hard link `./dat2330_04w.tar' to `/d2/dat2330_04w.tar':
Invalid cross-device link

Creating a symbolic link works without errors.

6.a the colon :
6.b 7, viz. loginname, encrypted password, UID, GID, Real Name, Home dir, Shell
6.c 103 (wc -l /etc/passwd)

6.d 6

/bin/bash
/bin/false
/bin/sash
/bin/sh
/bin/sync
/bin/tcsh

6.e yes
7. February 1, 2006
8. the owner can change the permissions on the file with chmod.
```
chmod u+rwx jobs_list
```
or
```
chmod u=rwx
	jobs_list
```
9.
```
drwx------    2 root     root        16384 Jun 19  2003 lost+found/
drwx------   14 root     root         4096 Feb 25 13:59 root/
```
All the other directories provide r-x permissions. The above shown directories only give access to the user/owner of the directories (the root user).

10.

command	owner (jenny)	group (pubs)	other
cd correspond/business/milk_co	change current dir to correspond/business/milk_co	change current dir to correspond/business/milk_co	error message: current dir not changed
ls -al correspond/business	error message: permission denied	error message: permission denied	error message: permission denied
cat correspond/business/cheese_co	displays the contents of cheese_co	displays the contents of cheese_co	error message: permission denied

Q: 6. Put on a line the word "advanced" by itself, then answer questions 12, 13, 15 and 18, chapter 4, pages 105-106. A: in sequence

12. the parent directory. the root directory
13.
```
touch ./-i
```
an argument that starts with a dash is interpreted by the touch command as an option, not as a filename.
```
rm ./-i
```
15.
```
ls -i | sort -n
```
18. the directory dirtmp contains hidden files (files that start with a dot. these are not displayed by the "ls" command, nor can they be removed with the "*" pattern.

Q: 7. Submit using the datsubmit command A: datsubmit 03 exercise03answers.txt