Linux Command sharing-New user and Group commands

The roles of Linux users are identified by UID and GID.

UID user ID: equivalent to a separate ID card, which is unique in the system

GID group ID: equivalent to your own family or your school.

1. The commands for creating a user and setting a password are as follows:

Useradd [parameter] user name

-g genus group

-u set uid

-m create home directory

-M has no home directory

-G specifies that it belongs to multiple groups

-s specifies login shell

-d specify home directory

-c comment

-D change its default properties

-e the date specified is the date on which the account expires

You can man useradd in xshell.

Examples are as follows:

Useradd-c "admin"-m abc

Explanation: create an ordinary abc user with a comment "admin" and automatically create a home directory.

2. Use the passwd command to set the password and modify the user password for the new user:

Passwd parameter user name

-l: lock the name of the named account

-u: unlock the account lock status

-x,-- maximum=DAYS: maximum password usage time (days)

-n,-- minimum=DAYS: minimum password usage time (days)

-d: delete the user's password

-S: check the password authentication type of the specified user

-- stdin: non-interactive change / set password. The disadvantage is that the operation log can check the password and kill it with history-c.

Example:

Passwd user name echo 123345 | passwd-- stdin user name

Note: when we delete a user's password, we do not need a password to log in.

3. Modify the user:

Usermod parameter user name

-c: modify the remarks of the user's account.

-d: modify the directory when the user logs in.

-e: modify the validity period of the account.

-f: change the number of days after the password expires to close the account.

-g: modify the group to which the user belongs.

-G: modify the additional group to which the user belongs.

-l: modify the user account name.

-L: locks the user's password so that the password is invalid.

-s: modify the shell used by users after logging in.

-u: modify the user ID.

-U: unlock the password.

Common parameters include-c,-d,-m,-g,-G,-s,-u, and-o, which, like the options in the useradd command, can specify a new resource value for the user.

Examples are as follows:

The common option for the user name of the userdel parameter is-r, which deletes the user's home directory together. Userdel-r abc

5. Create a user group:

Groupadd parameter user group name

-g: specify the gid of the new user group

-r: create a system workgroup. The group ID of the system user is less than 500mm.

-K: overwrite the configuration file "/ ect/login.defs"

-o: allows you to add workgroups whose group ID number is not unique.

Example:

Groupadd-g 344 bqh

Explanation: create a bqh group with an id of 344.

6. Reorganize:

Groupmod parameter user group name

-g: GID specifies a new group identification number for the user group.

-o: when used in conjunction with the-g option, the new GID of the user group can be the same as the GID of the existing user group on the system.

-n: new user group changes the name of the user group to a new name

Example:

Groupmod-g 356-n bqh2 bqh

Explanation: change the name of the user group bqh to bqh2, and the group gid to 356.

7. Delete a user group:

Groupdel user name

Example:

Groupdel bqh2

User query related commands:

Id / / query user information, such as which user group the user belongs to, and uid and gid, etc.

W / / to see who has logged in and what has been done, the switch is not good, only if you log in again.

Who / / check which users are logging in, terminal and login time, source host.

Users / / only shows which users are logged in.

Last / / shows a list of users who have logged in and logged out

Last log / / you can check whether any users have logged in to the system (accounts that are not enabled)

Original address: https://www.linuxprobe.com/linux-creat-group.html