How to view and modify file read and Write permissions under Linux system

To view file permission statements:

In Terminal input:
Ls-l xxx.xxx (xxx.xxx is the file name)

Then there will be similar messages, mostly these:
-rw-rw-r--

A total of 10 digits

Which: the front one-represents the type

The middle three rw-represents the owner (user)

Then those three rw-represent groups (group)

The last three r--represent others (other).

And then I'll explain the 9 digits in the back:

R indicates that a file can be read (read)

W indicates that the file can be written (write)

x indicates that the file can be executed (if it is a program)

-Indicates that the appropriate permission has not been granted

Now it's time to talk about modifying file permissions.

In Terminal input:

chmod o W xxx.xxx

Give other people permission to write xxx.xxx this file

chmod GO-RW xxx.xxx

Represents the deletion of read and write permissions for groups and others in xxx.xxx

which

U on behalf of owner (user)

G represents the group where the owner resides

O stands for others, but not u and g (other).

A represents all people, including U,g and O.

R indicates that a file can be read (read)

W indicates that the file can be written (write)

x indicates that the file can be executed (if it is a program)

Where: Rwx can also be replaced by numbers

R------------4

W-----------2

X------------1

-------------0

Let's go:

Represents the Add permission

-Indicates delete permission

= indicates a permission to make it unique

When we all understand the above, then we often have some of the following permissions are easy to understand:

-RW-------(600) Only the owner has read and write permissions

-rw-r--r--(644) Only the owner has read and write permissions, and the group and other people only have Read permissions

-RWX------(700) Only the owner has read, write, execute permissions

-rwxr-xr-x (755) Only the owner has read, write, execute permissions, groups and other people only read and Execute permissions

-rwx--x--x (711) Only the owner has read, write, execute permissions, groups and other people only execute the permissions

-rw-rw-rw-(666) Everyone has access to read and write

-RWXRWXRWX (777) Everyone has access to read and write and execute

Linuxfile and Directory access permissions settings

Usechmodand numbers to change the access rights of a file or directory
Permissions for files and directories are represented by the rwx three characters to represent the permissions of the owner, user group, and other users. Sometimes, characters seem to be too cumbersome, so there is another way to represent permissions in numbers, and only three numbers are required.
R: Corresponding value 4
W: Corresponding value 2
x: Corresponding value 1
-: Corresponding value 0
The key to digital setting is the value of mode, at first many beginners will be confused, in fact, it is very simple, we will rwx as a binary number, if there are 1 said, no 0 said, then rwx r-x R-can be expressed as:
111 101 100
Then convert every three bits into a decimal number, which is 754.
For example, we want a.txt this file to have the following permissions:
Other users of the same group as themselves
Is readable yes Yes Yes
Can be written yes Yes
Executable
So, we first get permission string according to the above table: rw-rw-r--, then convert to binary number is 110 110 100, and then every three bits into a decimal number, we get 664, so we execute the command:
[Email protected] ~]# chmod 664 a.txt
According to the above rules, rwx together is 4 2 1=7, a file with a rwxrwxrwx permission, the value is 777, and the file "---------" with a completely open permission is represented as 000. Here are a few examples:
-RWX------: equals the number represents 700.
-rwxr-r--: equals the number represents 744.
-rw-rw-r-x: equals the number represents 665.
Drwx-x-x: equals the number represents 711.
DRWX------: equals the number represents 700.
In text mode, you can execute the chmod command to change permissions on files and directories. Let's take a look at the ls-l in the directory:
[Email protected] ~]# ls-l
Total dosage 368
-rw-r--r--1 root root 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
You can see that the permissions of the file Conkyrc.sample file are 644, and then change the permissions of this file to 777. Execute the following command
[Email protected] ~]# chmod 777 Conkyrc.sample
Then ls-l look at the results after the execution:
[Email protected] ~]# ls-l
Total dosage 368
-rwxrwxrwx 1 root root 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
You can see that the permissions for the Conkyrc.sample file have been modified to rwxrwxrwx
If you want to add special permissions, you must use a 4-digit number to represent it. The corresponding values for special permissions are:
s or S (SUID): Corresponds to the value 4.
s or S (SGID): corresponds to the value 2.
T or T: corresponds to the value 1.

Use the same method to modify the file permissions.
For example:

[Email protected] ~]# chmod 7600 conkyrc.sample
[Email protected] ~]# ls-l
Total dosage 368
-rws--s--t 1 root root 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
Add the permission to modify all the files in a directory at once, including the file permissions in subdirectories to be modified, to use the parameter-R to initiate recursive processing.
For example:
[[email protected] ~]# chmod 777/home/user Note: Set the/home/user directory to rwxrwxrwx only
[[email protected] ~]# chmod-r 777/home/user Note: The permissions for the entire/home/user directory and its files and subdirectories are set to RWXRWXRWX

Use the command chown to change the ownership of a directory or file
Files and directories can not only change permissions, their ownership and user groups can also be modified, and set permissions similar to the user can be set through the graphical interface, or execute the chown command to modify.
Let's take a look at the contents of Ls-l first:
[Email protected] ~]# ls-l
Total dosage 368
-rwxrwxrwx 1 root root 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
You can see that the owning user group for the conkyrc.sample file is root and the owner is root.
Execute the following command to transfer ownership of the Conkyrc.sample file to the user:
[Email protected] ~]# chown user conkyrc.sample
[Email protected] ~]# ls-l
Total dosage 368
-rwxrwxrwx 1 user root 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
To change the owning group, you can use the following command:
[Email protected] ~]# chown:users conkyrc.sample
[Email protected] ~]# ls-l
Total dosage 368
-RWXRWXRWX 1 user users 12172 August 23:18 conkyrc.sample
Drwxr-xr-x 2 root root 48 September 4 16:32 Desktop
-r--r--r--1 root root 331844 October 21:08 libfreetype.so.6
Drwxr-xr-x 2 root root 48 August 22:25 MyMusic
-rwxr-xr-x 1 root root 9776 November 5 08:08 Net.eth0
-rwxr-xr-x 1 root root 9776 November 5 08:08 net.eth1
-rwxr-xr-x 1 root root 512 November 5 08:08 Net.lo
Drwxr-xr-x 2 root root 48 September 6 13:06 VMware
To modify permissions for a directory, use the-R parameter, as you did before.

How to view and modify file read and Write permissions under Linux system