How to create a new user under Linux

How to create a new user under Linux

In a Linux system, only the root user has permission to create other users.
The creation process is as follows:
useradd-d/home/newuser NewUser (Set the user's home directory and user name)
useradd-d/home/newuser-g 0-g 0,1,3,4,6,10-u 500-r-P love NewUser (Specifies the user's group ID and a list of the IDs, user IDs, passwords, etc.) of the owning group

To explicitly set a password for a user

Command for passwd username;
[Email protected] ~]# passwd hudamin
Changing password for user hudamin.
New UNIX Password:
Bad password:it are too short
Retype new UNIX Password:
Passwd:all authentication tokens updated successfully.

When the system is logged in, it will prompt the user home directory is not created, so there is a lack of a step, that is, for the corresponding user to create a belong to the user's home directory, create a time to note that because the new user's home directory is created by root, but the Linux system requires the owner of the home directory must be the user itself , therefore, after you create the home directory with root, you need to replace the owner with the new user itself. The command is as follows:

SU username

mkdir-p/home/newuser
Chown Newuser:newuser/home/newuser

This allows you to log in with NewUser ...

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Create users under Linux
1. Add FTP User
Useradd ftpname-d/home/ftp
passwd ftppwd
The following operations are performed with root privileges:
Service vsftpd start starts the Linux-brought FTP service

2. Add a normal user
Useradd Nagios–d/usr/local/nagios
Chown Nagios.nagios/usr/local/nagios
To switch users to Nagios users, add Nagios Access users:
Su Nagios
Htpasswd–c/usr/local/nagios/etc/htpasswd.users Nagiosadmin
You will be prompted to enter two passwords, for example, two times to enter Nagios.
Note: This is the first time the user is created and requires the "-C" option, which means creating a file that holds the user name and password, without the "-C" option when adding users or modifying passwords again.

Add a new user account using the Useradd command with the following syntax:

　　Useradd option User Name

Each of these options has the following meanings:

　　-C Comment Specifies an annotative description.

The-D directory specifies the home directory, and if this directory does not exist, the-m option can be used to create the master directory.

The-G user group specifies the user group to which the user belongs.

-G user Group, user group specifies the additional group to which the user belongs.

-S Shell file specifies the user's login shell.

　-u user number specifies the user's user number, and if you have the-o option, you can reuse the other user's identification number.

USERNAME Specifies the login name of the new account.

For example:

　　# useradd–d/usr/sam-m Sam

　　This command creates a user Sam, where the-D and-m options are used to generate a home directory for the login Sam/usr/sam (/usr is the parent directory where the default user home directory resides).

# useradd-s/bin/sh-g group–g adm,root Gem

This command creates a new user gem, which is the login shell of/bin/sh, which belongs to the group user groups, and also to the ADM and root user groups, where group user groups are their primary groups.

Add user account is in the/etc/passwd file to add a record for the new user, while updating other system files such as/etc/shadow,/etc/group and so on. The contents of these files will be described in detail later.

Linux provides an integrated system management tool, userconf, which can be used to manage user accounts uniformly.

If a user's account is no longer in use, it can be removed from the system. Deleting a user account is to delete the user record in the system files such as/etc/passwd, and delete the user's home directory if necessary. Delete an existing user account using the Userdel command , in the following format:

　　Userdel option User Name

The common option is-r, which is to remove the user's home directory.

For example:

# Userdel Sam

　　This command removes the user Sam's records in the system files (mainly/etc/passwd,/etc/shadow,/etc/group, etc.) while deleting the user's home directory.

Modify user account is based on the actual situation to change the user's relevant attributes, such as user number, home directory, user group, login shell and so on.

　　Modify the information for an existing user using the Usermod command, which is in the following format :

Usermod option User Name

　　Common options include-C,-D,-M,-G,-G,-S,-u, and-O, etc., which have the same meaning as the options in the Useradd command, specifying a new resource value for the user. In addition, some systems can use the following options:

-L New User name

This option specifies a new account that will change the original user name to the new one.

For example:

# usermod-s/bin/ksh-d/home/z–g developer Sam

This command modifies the user Sam's login shell to Ksh, the home directory to/home/z, and the user group to developer.

An important part of user management is the management of user passwords. The user account has just been created without a password, but is locked by the system, cannot be used, it must be given a password before it can be used, even if a blank password is specified.

The shell command that specifies and modifies the user's password is passwd. A superuser can specify a password for himself and another user, and a normal user can only use it to modify his or her password. The format of the command is:

　　passwd option User Name

Options available for use:

　　-L locks the password, which disables the account.

-u password to unlock.

-D make the account no password.

-F forces the user to modify the password the next time they log on.

If the default user name, the password for the current user is modified.

For example, assuming the current user is Sam, the following command modifies the user's own password:

$ passwd

Old password:******

New password:*******

Re-enter New password:*******

If you are a superuser, you can specify the password for any user in the following form:

# passwd Sam

New password:*******

Re-enter New password:*******

Ordinary users to modify their own password, the passwd command will first ask the original password, verify and then ask the user to enter two times the new password, if the password two times the same, the password is assigned to the user, and the superuser to specify a password for the user, you do not need to know the original password.

For system security, the user should choose a more complex password, for example, preferably with a 8-bit long password, the password contains uppercase, lowercase letters and numbers, and should be different from name, birthday, and so on.

　When you specify an empty password for a user, the following forms of command are executed:

# passwd-d Sam

　　This command removes the password for the user Sam so that the next time the user Sam logs on, the system will no longer ask for the password .

The passwd command can also lock a user with the-l (lock) option so that it cannot log on, for example:

# passwd-l Sam

How to create a new user under Linux