Acess Control List

Access Control List (ACL) is a more flexible and fine-grained permission management mechanism, used to define and control the access permissions of file system objects. Compared to traditional file permission systems, ACL provides more detailed permission control, allowing you to set specific permissions for different users and user groups, no longer limited to the traditional three roles (Owner, Group, Others).

Installation

If not installed, you can use the following command.

sudo apt-get install acl

Getfacl

Get the access control list of a file

getfacl - get file access control lists

Usage Example

Get the ACL information of the foo file.

getfacl foo

# file: foo
# owner: kuga
# group: kuga
user::rw-
group::rw-
other::r--

Setfacl

Set the access control list of a file.

setfacl - set file access control lists

Specify User Authorization

The soda user adds read and write permissions to the foo file.

setfacl -m u:soda:rw foo

getfacl foo

# file: foo
# owner: kuga
# group: kuga
user::rw-
user:soda:rw-
group::rw-
mask::rw-
other::r--

Specify Group Authorization

The soda group adds read and write permissions to the foo file.

setfacl -m g:soda:rw foo

getfacl foo

# file: foo
# owner: kuga
# group: kuga
user::rw-
user:soda:rw-
group::rw-
group:soda:rw-
mask::rw-
other::r--

Other Authorization

Add read and write permissions to the foo file for others.

setfacl -m o::rw foo

getfacl foo

# file: foo
# owner: kuga
# group: kuga
user::rw-
user:soda:rw-
group::rw-
group:soda:rw-
mask::rw-
other::rw-

Authorization Modification

The command is in the form of override.

setfacl -m o::r foo

other::rw- will become other::r--.

Clear Authorization

setfacl -m u:soda:- foo

setfacl -m o::- foo

user:soda:---
other::---

Delete Authorization

setfacl -x u:soda foo

setfacl -m g:soda foo

The two lines user:soda and group:soda will be deleted.

End of Line +

For files using ACL, there will be a + sign after the permission column.

-rw-rw-r--+