Question

Objective:

Practice common UNIX commands.

Procedure:

1. The following list of Unix commands are given for self-learning. Use 'whatis' or 'man' command to find out about each command. Your document should include the description or screen shots of the output from each of the command.

Commands:

1. df
2. du
3. gzip
4. file
5. history
6. wget

2. Changing access rights:

chmod u+x Dir1.0            adds execute permission for the owner

chmod go-w file1              removes write permission for the group and others

chmod ugo=rw testfile     sets the permissions for everyone to read and write, but not execute

chmod u=rwx newDir      sets the permissions for the owner to read, write, and execute

1. How to check access rights for files or directories?

• 2. Use the command in (a) to find out the access rights for the file named /etc/passwd.
• Who is the owner of this file?
• What is the permission for the group on this file?

Answer 1

Q.1 How to check access rights for files or directories?
Answer:
command :- "ls -l" or "ls -al"
'ls' is used for list all the files
'-l' used to get more information about the files in a directory,
'-la' options can be used to get all the details of the hidden files:

command output:

$ ls -la /root
total 24
drwxr-xr-x 2 root root 4096 2009-12-16 01:10 .
drwxr-xr-x 23 root root 4096 2010-02-18 10:14 ..
-rw------- 1 root root 123 2010-01-21 15:49 .bash_history
-rw-r--r-- 1 root root 2227 2007-10-20 11:51 .bashrc
-rw-r--r-- 1 root root 141 2007-10-20 11:51 .profile
-rw------- 1 root root 868 2009-12-16 00:47 .viminfo

if you want to check the access rights of /root directory then try above command.

(.) refers to the directory itself where as (..) refers to the parent directory and all other files individual lines refer to information about the different files present inside the directory.

Permissions for files are represented r,w and x which is the intial parameter of each lines
r refers to the read permission.
w refers to the write permission.
x refers to the execute permission.

lets take an exmple of below lines.

   rwxr-xr-x 2 root root 4096 2009-12-16 01:10 . (Here the first character refers to file type .d means its a directory)

The next three of letters after the file type in a file list (rwx) shows the permissions for the user, or file owner.
i.e. he has all permissions to read write and execute.
The next three of characters shows the permissions for the group category.
i.e the group has only read and execute access
The last three of characters (r-x) shows the permissions for the final category

Q 2:Use the command in (a) to find out the access rights for the file named /etc/passwd.
Answer:
$ ls -la /etc/passwd

Q 3:Who is the owner of this file?
Answer:
try this command
$ ls -l filename
output : rwxr-xr-x 2 sampleUser root 4096 2009-12-16 01:10
Here the 'sampleUser' is the owner of the file.

Q 4 :What is the permission for the group on this file?
Answer:
lets understand in the below output.
drwxr-xr-x 2 root root 4096 2009-12-16 01:10 .
Here group permission starts from 5th to 7th character i.e. 'r-x'.