Linux file attributes and related commands

1. Detailed explanation of file attributes

drwxr-xr-xProperties are mainly divided into 4 parts:

first part

The first letter, indicating the file type

1. d means directory
2. — for ordinary files
3. b represents input and output devices (random access devices)
4. l means link file
5. c represents the serial port device in the device file, such as keyboard, mouse (one-time read device)

part 2

From the 2nd character to the 4th character, indicating the file owner permission

part 3

From the 5th character to the 7th character, it means the permission of the file group

part 4

From the 8th character to the 10th character, indicating the authority of other users

Where r means read permission, w means write permission, x means execute permission, - means no permission

Second, change the file permission command chmod

There are two ways to set file attributes, one is numbers and the other is symbols.

For example, drwxr-xr-xthe permissions of the current test file are:

• owner - readable writeable executable
• User group - readable and executable, not writable
• Other users - readable and executable, not writable

1. Represented by numbers

 chmod [-R] xyz 文件或目录

Options and parameters:

• -R performs recursive (recursive) continuous changes, that is, all files in the subdirectory will be changed
• Where xyz represents the permission number

Each permission symbol can be represented numerically:

• r : 4
• w : 2
• x : 1

The three permissions (r/w/x) of each identity (owner/group/others) need to accumulate scores. For example, when the permissions are -rwxr-xr-xscores:

• owner 4+2+1 = 7
• group 4+0+1 = 5
• others 4+0+1 = 5

When we change the permissions of the test.sh file, it is represented by numbers:

  chmod 755  test

If you want to change the permissions of the files in the directory together, execute

chmod -R 755 test

2. Represented by symbols

chmod [ugoa] [[+ / - / =] [rwx]] [文件名]

The + means to add permissions, - means to subtract permissions, = means to set permissions

The permissions of the test.sh above are represented by symbols -rwxr-xr-x:

 chmod u=rwx g=rx o=rx

3. The super user changes the file owner and associated group chown

注意:chown requires superuser rootprivileges to use, only superusers and file owners belonging to the group can change the file association group. Non-superusers may need to use the chgrp command if they need to set an association group.

1. Set the owner of test to user1:

   chown user1 test
   

2. Change the owner of test to root, and the group it belongs to is root:

    chown root:root test
   

3. Set the owner of all files and subdirectories in the current directory as root, and the user root of the group:

    chown -R root:root test
   

4. Ordinary users change the group chgrp to which the file belongs

Unlike the chown command, chgrp allows ordinary users to change the group to which a file belongs, as long as the user is a member of that group

1. Change the group attribute of the file to staff:

    chgrp staff test
   

2. Change the group of all files in the test directory to staff:

   chgrp -R staff test