Linux system Folders 644, 755, 777 permissions are set in detail, left to right, the first digit represents the permissions of the file owner, the second digit represents the permissions of the same group of users, and the third digit represents the permissions of the other user.
And the specific permissions are represented by a number, the Read permission equals 4, with R, the permission to write is equal to 2, with W, the execution of the permission equals 1, denoted by x;
Through the combination of 4, 2, 1, the following permissions are obtained: 0 (no permission); 4 (Read permission); 5 (4+1 | Read + execute); 6 (4+2 | Read + write); 7 (4+2+1 | Read + Write + execute)
Take 755 as an example:
The first bit 7 equals 4+2+1,rwx, the owner has read, write, execute permission;
The second bit 5 equals 4+1+0,r-x, the same group of users have read, execute permissions but no write permission;
Third bit 5, ditto, is also r-x, other users have read, execute permissions but do not have write permission.
Common Linux file permissions are listed below:
444 r–r–r–
RW ——-
644 rw-r–r–
666 rw-rw-rw-
rwx--
744 rwxr–r–
755 Rwxr-xr-x
777 Rwxrwxrwx
RWX permissions digital interpretation under Linux
Chmod can also use numbers to represent permissions such as chmod 777 file
The syntax is: chmod ABC file
Each of the a,b,c is a number that represents the permissions of the user, Group, and other respectively.
R=4,w=2,x=1
To rwx the attribute then 4+2+1=7;
To rw-the attribute then 4+2=6;
To r-x the property, 4+1=7.
Example:
chmod a=rwx File
And
chmod 777 File
Same effect
chmod ug=rwx,o=x File
And
chmod 771 File
Same effect
Use chmod 4755 filename to give this program root privileges
Linux Digital Permission Interpretation