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37.2.5. Explaining the Process
The following steps illustrate what happens if the command
useradd juan is issued on a system that has shadow passwords enabled:
- A new line for
juanis created in/etc/passwd. The line has the following characteristics:- It begins with the username
juan. - There is an
xfor the password field indicating that the system is using shadow passwords. - A UID greater than 499 is created. (Under Red Hat Enterprise Linux, UIDs and GIDs below 500 are reserved for system use.)
- A GID greater than 499 is created.
- The optional GECOS information is left blank.
- The home directory for
juanis set to/home/juan/. - The default shell is set to
/bin/bash.
- A new line for
juanis created in/etc/shadow. The line has the following characteristics:- It begins with the username
juan. - Two exclamation points (
!!) appear in the password field of the/etc/shadowfile, which locks the account.Note
If an encrypted password is passed using the-pflag, it is placed in the/etc/shadowfile on the new line for the user. - The password is set to never expire.
- A new line for a group named
juanis created in/etc/group. A group with the same name as a user is called a user private group. For more information on user private groups, refer to Section 37.1.1, “Adding a New User”.The line created in/etc/grouphas the following characteristics:- It begins with the group name
juan. - An
xappears in the password field indicating that the system is using shadow group passwords. - The GID matches the one listed for user
juanin/etc/passwd.
- A new line for a group named
juanis created in/etc/gshadow. The line has the following characteristics:- It begins with the group name
juan. - An exclamation point (
!) appears in the password field of the/etc/gshadowfile, which locks the group. - All other fields are blank.
- A directory for user
juanis created in the/home/directory. This directory is owned by userjuanand groupjuan. However, it has read, write, and execute privileges only for the userjuan. All other permissions are denied. - The files within the
/etc/skel/directory (which contain default user settings) are copied into the new/home/juan/directory.
At this point, a locked account called
juan exists on the system. To activate it, the administrator must next assign a password to the account using the passwd command and, optionally, set password aging guidelines.
