Linux change file and directory permissions issues

1. Fast Example Learning

Modify the permissions for all files under a directory, including files in subdirectories, as shown in the following example:

chmod 777 /home/user Note: only/home/chmod777 /home/user Note: Indicates that the entire/home/ The user directory and the permissions for the files and subdirectories in it are set to rwxrwxrwx

where the parameter-R indicates the start-up recursion process

2. chmod command parsing:

CHMOD uses 3 numbers to express the permissions of the user (the owner of the file or directory), the user group (the same group of users), and other users:

such as: chmod 777/test

The number 7 is the expression that has both read, write, and Execute permissions: Read--denoted by the number 4;

Write--represented by the number 2;

Implementation-represented by the number 1;

Follow the rules, such as the permissions you want to set the/test directory to:

To user-readable writable: 4 (Read) + 2 (write) = 6;

Readable executable for user group: 4 (Read) + 1 (execution) = 5;

Readable to other users only: 4 (read);

This allows you to use the command:

chmod 654/test

3. Permission resolution:

Three types of permissions for files:

Read file contents (r), write data to File (w), execute file As command (x)

Three types of permissions for the directory:

Read the name of the file contained in the directory (r);

Write the message to the directory (add and remove links to index points, W);

The search directory (which can use the directory name as the pathname to access the files and subdirectories it contains);

Specific Description:

1. 1. Users with read-only permissions cannot enter the directory with a CD: You must also have Execute permission to access it;
   2. Users with execute permission can access files under the directory only if they know the file name and have read rights;
   3. You must have read and Execute permissions before you can list the directory in LS, or use the CD command to enter the directory;
   4. There is a write permission to the directory to create, delete, or modify any file or subdirectory under the directory, even if the file or subdirectory belongs to another user;

Several common permission instances:

-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

Linux change file and directory permissions issues