It can be the name of a new user or the name of an existing user (or an user created before by newusers). In case of an existing user, the user's information will be changed, otherwise a new user will be created.
If the field is empty, an new (unused) UID will be defined automatically by newusers.
If this field contains a number, this number will be used as the UID.
If this field contains the name of an existing user (or the name of an user created before by newusers), the UID of the specified user will be used.
If the UID of an existing user is changed, the files ownership of the user's file should be fixed manually.
If this field contains the name of an existing group (or a group created before by newusers), the GID of this group will be used as the primary group ID for the user.
If this field is a number, this number will be used as the primary group ID of the user. If no groups exist with this GID, a new group will be created with this GID, and the name of the user.
If this field is empty, a new group will be created with the name of the user and a GID will be automatically defined by newusers to be used as the primary group ID for the user and as the GID for the new group.
If this field contains the name of a group which does not exist (and was not created earlier wbefore by newusers), a new group will be created with the specified name and a GID will be automatically defined by newusers to be used as the primary group ID for the user and Gs the ID for the new group.
If this field does not specify an existing directory, the specified directory is created, with ownership set to the user being created or updated and its primary group.
If the home directory of an existing user is changed, newusers does not move or copy the content of the old directory to the new location. This should be done manually.
newusers first tries to create or change all the specified users, and then write these changes to the user or group databases. If an error occurs (except in the final writes to the databases), no changes are committed to the databases.
During this first pass, users are created with a locked password (and passwords are not changed for the users which are not created). A second pass is used to update the passwords using PAM. Failures to update a password are reported, but will not stop the other password updates.
This command is intended to be used in a large system environment where many accounts are updated at a single time.
The options which apply to the newusers command are:
System users will be created with no aging information in /etc/shadow, and their numeric identifiers are choosen in the SYS_UID_MIN-SYS_UID_MAX range, defined in login.defs, instead of UID_MIN-UID_MAX (and their GID counterparts for the creation of groups).
The input file must be protected since it contains unencrypted passwords.
The following configuration variables in /etc/login.defs change the behavior of this tool:
GID_MAX (number), GID_MIN (number)
The default value is 0, meaning that there are no limits in the number of members in a group.
This feature (split group) permits to limit the length of lines in the group file. This is useful to make sure that lines for NIS groups are not larger than 1024 characters.
If you need to enforce such limit, you can use 25.
Note: split groups may not be supported by all tools (even in the Shadow toolsuite). You should not use this variable unless you really need it.
SYS_GID_MAX (number), SYS_GID_MIN (number)
SYS_UID_MAX (number), SYS_UID_MIN (number)
UID_MAX (number), UID_MIN (number)
useradd and newusers use this mask to set the mode of the home directory they create
login.defs(5), passwd(1), useradd(8).