13.1.3 Framework for Owner User and Owner Group of File
In Linux, users are grouped and managed according to certain criteria to grant or deny privileges to specific user account or user group of. When classifying the types of users who can be granted authority to files, there are three types as follows:
13.1.2 Confirming Permission Information on Window Screen
To confirm the details of a specific file on window screen, click right mouse buttpn on the desired file or directory, and then a pop-up screen will appear as shown in the figure below. Click the [Properties] menu there.
13.1 Understanding Scheme of File Permissions
13.1.1 Confirming Permission Information on File
If you confirm file information on Linux system, you can determine permissions for that file.
Below is the contents of a directory called “testdata” that you have seen with the [File Manager] program on the window screen. You can see that the directory contains a file and another directory.
Chapter 13 Control of File Permission
Chapter’s Main Topics
This chapter describes the basic concepts of how a permissions scheme for a file works on a Linux system, and also describes how to change ownership and execution permissions for a file.
It includes descriptions on the following topics:
■ Scheme of file permission
■ Changing the ownership of a file
■ Change execution permission on a file
12.7.7 Assignment of User Account to User Group
12.7.7.1 Review of Processing Method
If a user account is assigned to a user group, that user inherits all the responsibilities and privileges that the group has. Also, when a certain user group is given a certain responsibility and privilege, all users belonging to that user group are given the same responsibility and privilege.
12.7.6 “delgroup” Command – Delete User Group
You will need to delete user groups that are not needed on your system. When deleting a user group, be careful about the user accounts belonging to that group.
When deleting a user group, you can use “delgroup” and “groupdel” commands. The “delgroup” command makes it easy to create user groups. On the other hand, the “groupdel” command can handle relatively detailed processing with very low-level commands, but it is not used for general purposes because it is complex to use.
12.7.5 “addgroup” Command – Create User Group
You can use “addgroup” and “groupadd” commands to create user groups. The “addgroup” command makes it easy to create user groups. On the other hand, the “groupadd” command can handle relatively detailed processing with very low-level commands, but it is complex to use and is not used for general purposes.
12.7.4 Managing Relationship between User and User Group
Raspberry Pi uses several ways to manage the relationship between user groups and users.
If the user account is not assigned to a separate group, but is assigned only to its own self group, the primary group, the relationship is defined using “/etc/passwd” file.
12.7.3 Managing User Group
In the Raspberry Pi system, user groups are managed in “/etc/group” file. The managed data has the following format.
12.7.2 Relationship between User and User Group
In the Raspberry Pi system, certain user account is always assigned to a specific group. Also, certain user account can belong to more than one group at the same time.
If you do not specify a separate group for a specific user account, the user always belongs to the primary group, which is its own group. This primary group has the same name as its own user account, contains its own user account only, and is created automatically even if you do not create it separately.