A Lesson about UNIX drive storage.

1. UNIX drive storage
● There are no drive letters.
● The directory structure starts from the 'root' where
everything is seen as a file.
● Directories are simply 'mounted' into another folder.

2. The Unix / Linux / Apple filesystem
+-----+
| / |
+--+--+
|
+--------+---+-----+--------+
| | | |
+--+--+ +--+--+ +---+--+ +--+--+
| bin | | usr | | home | | etc |
+-----+ +-----+ +--+---+ +-----+
|
+-------------+-----+
| |
+---+--+ +---+--+
| FRED | | DAVE |
+---+--+ +---+--+
| |
+-----+---+ +----+-----+
| | | |
+---+--+ +---+--+ +--+---+ +---+--+
| work | | web | | work | | web |
+------+ +------+ +------+ +------+

3. File Permissions and file access.
In MS systems, files listed in Windows Explorer, File Manager (or
equivalent) have letters next to them to indicate their permission
status.
a - archive files
h - hidden files
r - read only files
s - system files

4. Unix files and permissions
drwx------ 2 dforbes EL 512 Dec 1 17:25 Mail
drwx------ 2 dforbes EL 512 Sep 2 1996 News
-rw-r--r-- 1 dforbes EL 7127 Nov 28 18:38 boot.txt
drwxr-x--- 3 dforbes EL 512 Sep 2 1996 dhf
drwxr-xr-x 7 dforbes EL 512 Sep 8 14:03 frames
-rw-r--r-- 1 dforbes EL 28774 Dec 1 14:08 hardware.txt
-rw-r--r-- 1 dforbes EL 3144 Nov 28 18:38 memory.txt
-rw-r--r-- 1 dforbes EL 15483 Nov 28 18:38 networks.txt
-rw-r--r-- 1 dforbes EL 53089 Nov 27 13:56 ports.html
drwx------ 9 dforbes EL 512 Oct 29 14:03 ugf
-rw-r--r-- 1 dforbes EL 5773 Nov 27 13:56 video.htm
-rw-r--r-- 1 dforbes EL 14762 Nov 27 13:56 work1.htm
/homedir/dforbes%

5. Unix permissions determine which files can be
altered, read or executed.
The permissions used are:
r - read access granted
w - write access granted
x - execute access granted

6. UNIX file listings have a set of 10 spaces where the letters r, w or x
are written to indicate WHO is allowed to read, write, or execute that
file.
- - - - - - - - - -
● The first space of the 10 may be left blank to indicate a file, or a
"d" used to indicate a directory, or “l” for a 'link'.
● The remaining 9 spaces are divided into three groups of three.

7. A file which allows:
● read, write and execute permission to the owner,
● read and execute to a group and
● read only to everybody else,
would look like this:
d r w x r - x r - -
In each group of 3 spaces,
● the first character determines the read permission,
● the second the write permission, and
● the third the execute permission.

8. So ::
● The first letter group refers to the permissions granted to the
owner of the file.
● The second, to a specific group of users who are granted
access rights to the file.
● The third letter group determines the access rights of anybody
else to the file.
These attributes can be changed by the owner of the file who
decides which users can have particular access.

9. chmod
To change the permission set up, the chmod command is used:
Each group of three permissions can be represented by an octal
number (0 to 7), (1 = set permission)
d r w x r - x r - -
Binary : 1 1 1 1 0 1 1 0 0
Octal : 4 + 2 + 1 4 + 0 + 1 4 + 0 + 0
= 7 5 4
Command used is: chmod 754 filename.
** Only the owner of the file can change these settings.
Other commands include:
● chgrp - for changing the group given access to the file
● chown - to change the owner of the file

10. Commercial Web filespace
ISP webspace hosting your own web domain, the industry standard access tool is FTP
The web root, eg http://www.somenet.com will be kept in a subdirectory
Every ISP puts this subdirectory in different places, eg.
http://splicehost.com/faq.html
PROGRAMS' LOCATION
- What is the path to PERL? /usr/bin/perl
- What is the path to SENDMAIL? /usr/sbin/sendmail
- What is the path to DATE? /bin/date
- What is the path of my files? /home/yourusername
- Web read-able files are in /home/username/public_html
However, you are only allowed to work from /public_html, and /home/username
is kept invisible to you.
NOTE: DRIVE LETTERS NEVER APPEAR - ONLY UNIX DIRECTORIES

11. So.
A Question.

12. What is the relationship
between
Windows drive letters
and
Internet web site URLs?

13. There is none.
There is no
relationship.

14. Drive letters have
nothing to do with the
Internet.

15. Absolutely nothing.

16. Internet file
naming rules are
UNIX