Linux Basic Knowledge

User Management

Linux Users And Groups: User and group description. About the type of user and the function of group.
How to check the Linux user list and about /etc/passwd file: Basic knowledge of Linux. How to check the user list. A description of the /etc/passwd file, /etc/shadow.
Linux Create a new user - useradd: Create a new user on Linux. How to check the default setting of the useradd command. Describe options for the useradd command. Explain how to change the default settings of newly created users.
Change Linux user information - usermod: About how to change user information and account information. Description of usermod command. I will explain the change of user's group, change of home directory, options, format and usage example.
Delete Linux user account - userdel: How to delete user account. User account delete command userdel description, format, options and examples. How to delete an account for each user's home directory, and how to delete all files that the user has.
How to check the Linux group list and about /etc/group file: About how to check the group list. How to output the group list. Description of login to group. Description of /etc/group file, /etc/gshadow.
Linux Create a new group - groupadd: Description of the groupadd command to create a new group. Descriptions of the options of the groupadd command and descriptions of the files modify by the "groupadd" command.
Change Linux group information - groupmod: A description of the command groupmod that makes changes to the group information.You can change the group name and GID with the groupmod command.Describes the options of the groupmod command and describes the files that are modified by the groupmod comma
Delete Linux group - groupdel: A description of the groupdel command to delete a group. About the files that the "groupdel" command changes.
Switch users by su command: How to switch users with the su command. Difference in behavior with or without option "-". Execute commands in a specific account environment.

File and Directory permission management

File and Directory access authority: Descriptions on file / directory access authority. I will explain how to check the set access privilege and how to view the displayed contents.
Symbolic notation and numerical notation of access right (permission): Explanation of symbolic notation and numerical notation of access permission (permission) of file / directory.
Change of access right (permission) - chmod: How to change file / directory access rights (permissions). Explains how to use chmod in detail.
Change ownership and groups of files and directories - chown: How to change file/directory ownership and groups, explaining the detailed usage of chown.
Changing file and directory groups - chgrp: How to change groups of files and directories, and how to use the chgrp command.
SUID (Set User ID) - Special access rights: Description of a special access right called SUID (Set User ID).
SGID (Set Group ID) - Special access rights: Description of a special access right called SGID (Set Group ID).
Sticky Bit - Special Access Rights: Sticky Bit - A description of special access rights.
Default access rights - umask: Describes the default access rights for files and directories, explains the umask value and how to set it.