Linux file and Directory permission descriptions

Permissions for files and directories are divided into: Read, write, execute, permission objects are divided into: creator, the same group as the creator, other users three classes, followed by "-" separated. To modify the permissions of a file or directory use the "chmod 588 file name" For 588 analysis: Each number represents an object, in order of the following: Creator permissions, same group user rights, normal user rights. 1 for the executable permission, 2 for the writable permission, 4 for the readable permission, so 588 in 5=1+4, indicating that the creator permission is executable readable, 8 cannot be divided so it will be displayed illegally. Another quick way to set it up is to use letters:

"A" means all users, "U" means the Creator, "G" means the creator with the same group of users, "O" for other users, "+" for the Add permission, "-" for the cancellation of permissions, "R" for Read permission, "W" for Write permission, "x" for write permission. For example: The chmod a-r file name indicates that all users do not have Read permissions.

Then comes an explanation of total 8, when using LS to see that it is often the number of things that will appear, which refers to the memory of this file or directory. The unit is Kbytes, and it is also noted that the concept of memory in all file systems is "block". This means that memory is always an integer multiple of block. A block occupies a memory size of 4k.

Linux file and Directory permission descriptions