8.6 Modifying Accounts

There are a variety of different commands available in the Unix environment to manipulate user accounts. The most common commands are summarized below, followed by more detailed examples of their usage.

Command Summary
adduser The recommended command-line application for adding new users.
rmuser The recommended command-line application for removing users.
chpass A flexible tool to change user database information.
passwd The simple command-line tool to change user passwords.
pw A powerful and flexible tool to modify all aspects of user accounts.

8.6.1 adduser

adduser is a simple program for adding new users. It creates entries in the system passwd and group files. It will also create a home directory for the new user, copy in the default configuration files (``dotfiles'') from /usr/share/skel, and can optionally mail the new user a welcome message.

To create the initial configuration file, use adduser -s -config_create. [1] Next, we configure adduser defaults, and create our first user account, since using root for normal usage is evil and nasty.

Example 8-1. Configuring adduser

    # adduser -v
    Use option ``-silent'' if you don't want to see all warnings and questions.
    Check /etc/shells
    Check /etc/master.passwd
    Check /etc/group
    Enter your default shell: csh date no sh tcsh zsh [sh]: zsh
    Your default shell is: zsh -> /usr/local/bin/zsh
    Enter your default HOME partition: [/home]:
    Copy dotfiles from: /usr/share/skel no [/usr/share/skel]: 
    Send message from file: /etc/adduser.message no 
    [/etc/adduser.message]: no
    Do not send message
    Use passwords (y/n) [y]: y
    
    Write your changes to /etc/adduser.conf? (y/n) [n]: y
    
    Ok, let's go.
    Don't worry about mistakes. I will give you the chance later to correct any input.
    Enter username [a-z0-9_-]: jru
    Enter full name []: J. Random User
    Enter shell csh date no sh tcsh zsh [zsh]: 
    Enter home directory (full path) [/home/jru]: 
    Uid [1001]: 
    Enter login class: default []: 
    Login group jru [jru]: 
    Login group is ``jru''. Invite jru into other groups: guest no 
    [no]: wheel
    Enter password []: 
    Enter password again []: 
    
    Name:     jru
    Password: ****
    Fullname: J. Random User
    Uid:      1001
    Gid:      1001 (jru)
    Class:    
    Groups:   jru wheel
    HOME:     /home/jru
    Shell:    /usr/local/bin/zsh
    OK? (y/n) [y]: y
    Added user ``jru''
    Copy files from /usr/share/skel to /home/jru
    Add another user? (y/n) [y]: n
    Goodbye!
    #

In summary, we changed the default shell to zsh (an additional shell found in the Ports Collection), and turned off the sending of a welcome mail to added users. We then saved the configuration, created an account for jru, and made sure jru is in wheel group (so that she may assume the role of root with the su command.)

Note: The password you type in is not echoed, nor are asterisks displayed. Make sure you do not mistype the password twice.

Note: Just use adduser without arguments from now on, and you will not have to go through changing the defaults. If the program asks you to change the defaults, exit the program, and try the -s option.

8.6.2 rmuser

You can use rmuser to completely remove a user from the system. rmuser performs the following steps:

  1. Removes the user's crontab(1) entry (if any).

  2. Removes any at(1) jobs belonging to the user.

  3. Kills all processes owned by the user.

  4. Removes the user from the system's local password file.

  5. Removes the user's home directory (if it is owned by the user).

  6. Removes the incoming mail files belonging to the user from /var/mail.

  7. Removes all files owned by the user from temporary file storage areas such as /tmp.

  8. Finally, removes the username from all groups to which it belongs in /etc/group.

    Note: If a group becomes empty and the group name is the same as the username, the group is removed; this complements the per-user unique groups created by adduser(8).



rmuser cannot be used to remove superuser accounts, since that is almost always an indication of massive destruction.

By default, an interactive mode is used, which attempts to make sure you know what you are doing.

Example 8-2. rmuser Interactive Account Removal

    # rmuser jru
    Matching password entry:
    jru:*:1001:1001::0:0:J. Random User:/home/jru:/usr/local/bin/tcsh
    Is this the entry you wish to remove? y
    Remove user's home directory (/home/jru)? y
    Updating password file, updating databases, done.
    Updating group file: trusted (removing group jru -- personal group is empty) done.
    Removing user's incoming mail file /var/mail/jru: done.
    Removing files belonging to jru from /tmp: done.
    Removing files belonging to jru from /var/tmp: done.
    Removing files belonging to jru from /var/tmp/vi.recover: done.
    #

8.6.3 chpass

chpass changes user database information such as passwords, shells, and personal information.

Only system administrators, as the superuser, may change other users' information and passwords with chpass.

When passed no options, aside from an optional username, chpass displays an editor containing user information. When the user exists from the editor, the user database is updated with the new information.

Example 8-3. Interactive chpass by Superuser

    #Changing user database information for jru.
    Login: jru
    Password: *
    Uid [#]: 1000
    Gid [# or name]: 1000
    Change [month day year]:
    Expire [month day year]:
    Class:
    Home directory: /home/jru
    Shell: /usr/local/bin/tcsh
    Full Name: J. Random User
    Office Location:
    Office Phone:
    Home Phone:
    Other information:

The normal user can change only a small subset of this information, and only for themselves.

Example 8-4. Interactive chpass by Normal User

    #Changing user database information for jru.
    Shell: /usr/local/bin/tcsh
    Full Name: J. Random User
    Office Location:
    Office Phone:
    Home Phone:
    Other information:

Note: chfn and chsh are just links to chpass, as are ypchpass, ypchfn, and ypchsh. NIS support is automatic, so specifying the yp before the command is not necessary. If this is confusing to you, do not worry, NIS will be covered in Chapter 17

8.6.4 passwd

passwd is the usual way to change your own password as a user, or another user's password as the superuser.

Note: Users must type in their original password before changing their password, to prevent an unauthorized person from changing their password when the user is away from their console.

Example 8-5. Changing Your Password

    % passwd
    Changing local password for jru.
    Old password:
    New password:
    Retype new password:
    passwd: updating the database...
    passwd: done

Example 8-6. Changing Another User's Password as the Superuser

    # passwd jru
    Changing local password for jru.
    New password:
    Retype new password:
    passwd: updating the database...
    passwd: done

Note: As with chpass, yppasswd is just a link to passwd, so NIS works with either command.

8.6.5 pw

pw(8) is a command line utility to create, remove, modify, and display users and groups. It functions as a front end to the system user and group files. pw has a very powerful set of command line options that make it suitable for use in shell scripts, but new users may find it more complicated than the other commands presented here.

Notes

[1]

The -s makes adduser default to quiet. We use -v later when we want to change defaults.

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