CentOS File Permissions Learn notes

Let's take a look at an example:

[root@local opt] #ls-al

The Ls-al command is all files that list directories, including hidden files. The filename of the hidden file is the first character '. '

-rw-r--r--1 root root 08-02 14:54 gtkrc-1.2-gnome2
-RW-------1 root root 189 08-02 14:54 iceauthority
-RW-------1 root 08-05 10:02. lesshst
drwx------3 root root 4096 08-02 14:54. metacity
Drwxr-xr-x 3 root root 4096 08-02 14:54 Nautilus

The columns of the list are defined as follows:

[Permission Property Information] [Number of connections] [Owned by] [Owner owned user Group] Size [Last Modified time] FileName

The list of permission attributes is 10 characters:

The first character represents the file type, D is the directory-for the normal file L for connect b for the storage interface device C for keyboard mouse input devices
2, 3, 4 characters for owner permission, 5, 6, 7 characters for owner same group User rights, 8, 9, 10 for other user rights
The second character represents the owner Read permission, or R if it has permission, or-
The third character represents the owner write permission, or W if it has permission, or-
The fourth character represents the owner execution permission, or X if it has permission, or-
The fifth character indicates that the owner has the same group of users Read permissions, or R if they have permission, or-
The sixth character indicates that the owner has the same group of users write permission, or W if the permission is-
The seventh character indicates that the owner has the same group of users to execute the permission, if the permission is x, and no permission is-
The eighth character indicates other read permissions other than the same group, if the permission is R, and no permission is-
The nineth character indicates other write permissions that are not in the same group, or W if they have permissions, or-
The tenth character represents other permissions that are not in the same group, if the permission is x, and no permission is-

To modify a file-owning group command:

[root@local opt] #chgrp [-r] Group name file name

Where-R is recursively set

To modify the owner and group commands for a file:

[root@local opt] #chown [-r] User [: User Group] File name

To modify File access Permissions command:

[root@local opt] #chmod [-r] 0777 filename

Here's a example of setting file permissions for the user

To view basic information about a file:

-~/.BASHRC 
-rw-r--r--1 bailing bailing 71901-09 21:08/home/ bailing /. BASHRC

Ls-l output Basic file information:

Output Columns	Description
-rw-r--r--	File access permissions.
1	The number of hard connections is 1.
Bailing bailing	Group and user information for the file attribution.
719	Size of file (in bytes).
01-09 21:08	File modification time.
/home/bailing/.bashrc	Filename.

File access rights

The character of the file access permission is represented by:

character	Description	Sample
-	Regular files.	~/.bashrc
D	Directory.	Ls-ld/tmp
L	Symbolic connections.	/dev/stdin->/proc/self/fd/0
C	Character device files.	/dev/console
D	Block device files.	/dev/sda
P	Named pipes.
S	The socket file.	/tmp/mysql.sock

Umask

At the beginning of each file creation, there is a default access right (the file creation mask). The default value for the file is 0666, and the default value for the directory is 0777. The default access rights are affected by umask, and umask limits which permissions should not be granted.

View the value of the Umask (0002 for other not writable):

$ umask 
 0002

View the symbol representation for umask (-s To view the permissions that can be granted):

- S
u=rwx,g=rwx,o = Rx

Create 1 Files:

$ > /tmp/um.txt $ ls-L/tmp/um.txt-RW-RW-R-- 1bailing bailing0  -- -  One: to /tmp/um.txt

Um.txt's initial permission is 0666, whereas Umask is 0002, and the two operations are: 0664, so the final file permission is: 0664 (-rw-rw-r--).

To modify the value of Umask:

$ umask U = rwx , g =, o =

To view the value of the new umask:

$ umask 
 0077  
-S u = rwx, G =, o 
  =

To create a new file and view permissions:

$ > /tmp/um.txt $ ls-L/tmp/um.txt-RW------- 1bailing bailing0  -- -  One:Panax Notoginseng /tmp/um.txt