Day 6 Task:
File Permissions and Access Control List
Understanding file permissions is essential for any Linux user or administrator. Linux employs a robust and flexible file permission system that dictates who can access, modify, or execute files and directories. Let's delve into the intricacies of Linux file permissions with a comprehensive guide, exploring the basics, permission types, and practical tips for effective management.
There are three basic types of permissions:
Read (r): If the read permission is granted, the file can be opened and its contents can be viewed.
Write (w): If the write permission is granted, the file can be modified or deleted.
Execute (x): If the execute permission is granted, the file can be executed as a program or script.
File permissions are usually set for three classes of users:
Owner (u): The person who owns the file.
Group (g): The group associated with the file.
Others (o): Everyone else who is not the owner or in the group.
Permissions are often represented as a string of characters, such as "rwxr-xr--". In this example:
The first three characters represent the owner's permissions (read, write, execute).
The next three characters represent the group's permissions (read, execute, no write).
The last three characters represent the others' permissions (read, no execute, no write).
Numeric representation (octal) is another common way to express permissions:
Read (r): 4
Write (w): 2
Execute (x): 1
So, "rwxr-xr--" in octal is 754.
To set permissions, you can use the chmod command in Unix-like systems. For example:
#chmod 754 filename
This command sets the file permissions to read, write, and execute for the owner (7), read and execute for the group (5), and read-only for others (4).
Remember to be cautious with file permissions, especially when dealing with sensitive files or system files, to ensure security and prevent unauthorized access or modifications.
#chmod 765 filename
Here we can understand File permissions through chart
Access Control List:
Access Control Lists (ACLs) provide a more flexible way of specifying permissions for files and directories beyond the traditional Unix file permissions. ACLs allow you to define permissions for specific users and groups beyond the owner, group, and others. This can be particularly useful in complex environments where traditional Unix permissions may not provide enough granularity.
Displays the Acl of a file or directory.
#getfacl filename
For example👇
Modifies the ACL of a file or directory.
#setfacl -m u:username:rwx filename
For example👇
Remove all the ACL permission of a file or directory.
#setfacl -b filename
For example👇
