linux-detailed user and group management

User Category:

Admin: 0

System users: 1-499

Ordinary users: the researcher

Group Category:

Administrators group: 0

System Group: 1-499

General Group: Researcher

Linux files related to users and groups:

/ETC/PASSWD: User's account information

/etc/shadow: User password and related account settings

/etc/group: Group account information

I../etc/passwd file

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The passwd file is composed of 7 parts, separated by the ":" Number.

Login account: Password dot: uid:gid: Comment Information: Home directory: Default Shell interface

Ii../etc/group Documents

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The group file consists of 4 parts, separated by the ":" Number.

Group name: group password dot: GID: A list of users that belong to this group (multiple users are separated by commas, and users with this group are listed as additional groups).

Iii../etc/shadow file

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The shadow file is composed of 9 parts, separated by the ":" Number.

User name: encrypted password (MD5 encryption): The last time the password was modified: password minimum Age: Password maximum age: Password Expiration warning interval: password inactivity period: Account expiration: Reserve an alternate area.

User Add Command: Useradd

-U UID: Specifies the UID to add

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-G GID: Specifies the base group for adding users

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-G GID: Specifies additional groups for adding users

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-C ' COMMENT ': Specify annotation information when adding users

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-d/path/to/somewhere: Specifies the user home directory.

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Note: The specified directory will have a warning message if it exists beforehand. The files in the home directory are copied from/etc/skel.

-S Shell: Specifies that the user uses that Shell interface, only the shell that exists in the/etc/shells file

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-r: Create System User (UID is between 1-499)

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Groupadd command:

-G GID: Specifies the GID to create the group

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-R: Creating a System Group

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passwd command:

Ordinary users can only modify their own password, the administrator is unrestricted.

Administrator to change the password format:

passwd [Username]

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Note: This example has a simple new password, so there is a reminder message.

-L: Lock user

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Note: The user is locked, the password field will have 2 in front of it!!

-U: Unlocking the user

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--stdin: Change password directly from standard input

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Userdel: Deleting users

-r: Delete user and home directory

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Groupdel: Deleting a group

Groupdel GROUPNAME

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Usermod: Modify User

-U uid: Modify user UID

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-G GID: Modify user base Group

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Note: The modified group must exist beforehand

-G: Modifies the user's additional group, which is typically used with-A to modify additional groups in an append manner. -A in front of-g

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-D: Modify the user home directory, which can be used with-m, to create a new home directory and move the user's home directory files to the new home directory.

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-S: Modify Shell interface

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-L: Modify user Name

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Note: This option is the same as CHSH username

To view user information:

ID username

-U: Show user ID

-G: Show basic groups

-G: Show all groups (include basic and additional groups)

-N: This option is displayed with a name instead of a digital display when used with other options above

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To modify a group:

Groupmod:

-G GID

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-N New_group_name

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This article is from "The Blood of the Linux blog" blog, please be sure to keep this source http://xuezhonghua.blog.51cto.com/10167373/1639276

linux-detailed user and group management