What files are created/modified when adding a user (useradd) in linux?

Question

I know that /etc/group and /etc/passwd are modified, and /home/user/* is created, but are there others?

Thanks.

Answer 1

It depends on what NSS system you're using. If it's a standard unix login, typically /etc/passwd and /etc/shadow only. /etc/group is only used if creating a new group or adding the user to supplementary groups.

The files from /etc/skel are typically copied into the new user's home directory, which need not be /home/user

Things such as mailboxes and crontabs are generally created in an on-demand basis, so not when the user is created (the mailbox is normally created when the user receives their first item of email)

Answer 2

That sounds like about it... As far as I know, other resources (like mail spools and crontabs) are all created on demand. The home directory (copied from /etc/skel) and passwd/group/shadow files are all that should be changed on use creation.