[Day 2] 1. More about File Systems

Disk Partition Conventions

In Windows

Hard Disk: Disk0, Disk1, ...
Partitions: C:, D:, E:, ...

In Linux

Hard Disk: sda, sdb, sdc, ...
Partitions: sda1, sda2, sda3, ...

drwxr-xr-x     1    sunbeam     sunbeam      4096     Sep 26 18:54  copy.txt

| drwxr-xr-x | 1 | sunbeam | sunbeam | 4096 | Sep 26 18:54 | copy.txt | | ------------------------------------------------------------------------------------- | ---------- | ---------------------- | ------------- | --------------------- | ------------ | ---------------- | | First letter 'd' denotes the type of file. The other characters indicate permissions. | Link Count | User/Owner of the file | Group of file | Size of file in bytes | Time Stamp | name of the file |

Types of Files in Linux

Regular File:
```
-
```
Directory File:
```
d
```
Link File:
```
l
```
Pipe File:
```
p
```
- Used for Inter-Process Communication (IPC).
- Example commands:
  - ```
  mkfifo fifo
```
  : Create a pipe file named
```
  fifo
```
  .
- ```
ls -l fifo
```
    : Check the type of file.
Socket File:
```
s
```
Character Special File:
```
c
```
- Data transfer is character by character; used by character devices.
Block Special File:
```
b
```
- Data transfer is block by block; used by block devices.

Groups in Linux

Group: A collection of users with shared permissions.
- Examples:
  - Students →
```
group1
```
  - Staff →
```
group2
```
  - Admins →
```
group3
```
Purpose of Groups: To assign permissions efficiently across users instead of individually.

File Ownership

When a user creates a file, they become the owner.
The file is assigned to the creator’s group.
- Example: If
```
student1
```
  (part of
```
group1
```
  ) creates
```
file.txt
```
  , it belongs to
```
group1
```
  .

File Permissions

Permission Types

Read (
r
): View the file.
Write (
w
): Modify the file.
Execute (
x
): Run the file (for scripts/programs).

Permission Categories

User (Owner):
```
rwx
```
,
```
rw-
```
, etc.
Group:
```
rwx
```
,
```
r--
```
, etc.
Others:
```
rwx
```
,
```
r--
```
, etc.

Understanding Permissions

```
-
```
means the permission is not granted.
Permissions follow an octal number system.

Example

String:
```
rw- rw- r--
```
Binary:
```
110 110 100
```
Octal Representation:
- User: 6
- Group: 6
- Others: 4
- Total:
```
0664
```
  (the leading
```
0
```
  indicates it's octal)
View Octal Representation: Use
```
stat <filename>
```
command.