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.TH NU 8
.SU
.SH NAME
nu \- manage user login accounts (create, modify, destroy Unix accounts)
.SH SYNOPSIS
.nf
.B /etc/nu -a
.B /etc/nu -m
.B /etc/nu -d
.B /etc/nu -k user1 user2 ...
.fi
.SH DESCRIPTION
.I Nu
is a program to help a Unix system manager create, modify, 
delete, and and destroy
accounts on that machine. While everything accomplished by \fInu\fR
can be done manually by editing files and issuing shell commands, \fInu\fR
will steer you through getting all the details right, worrying about file
locking, checking for typos, etc.
.PP
When \fInu\fR is run with the ``a'' option, it adds new accounts. The program
prompts you for the login id, password, name, and other information about
each new user, and then goes off and creates the account, creates its
directories, initializes their contents, and makes an entry in a log file.
.PP
When \fInu\fR is run with the ``m'' option, it modifies existing accounts. It
repeatedly asks for account names and instructions for the changes that you
want to make to those accounts, until you tell it that you are done making
changes. At that time it sorts the updated account records and merges them
all at once into /etc/passwd. 
.PP
When \fInu\fR is run with the ``d'' option, it deletes accounts while still
leaving an /etc/passwd entry for the deleted account. This will prevent that
uid from being reused, and will enable you to make sense out of accounting
data after deleting an account. The program repeatedly asks you for the names
of accounts to be deleted, and how much deleting you really want to do to
them.
.PP
When \fInu\fR is run with the ``k'' option and a list of login id's, it
deletes from the system almost all information pertaining to those login id's.
Specifically, it removes the entry from /etc/passwd, deletes the login
directory and all of its contents, and deletes the mailbox. It does not
currently remove that user from any mailing lists in /usr/lib/aliases.
The ``k'' option is not interactive: the complete list of accounts to be
deleted is provided on the command line after the ``\-k''.
.SH CONFIGURATION
When 
.I nu
is started up, it reads configuration commands from the file /etc/nu.cf. This
file specifies the details of how new accounts are to be created on your
machine.  Typically you will need to change only the GroupHome declarations
in that  file, which declare the file systems that hold the login directories
for  members of different groups. However, you can change anything that you
find there if your system management policies require it.
.PP
When \fInu\fR wants to create a new directory, it runs a shell script named
in /etc/nu.cf. Similarly, when it wants to initialize the files in a
newly-created directory, it runs another shell script whose name it
determines from /etc/nu.cf. By way of configuration and customization, you
can edit those shell scripts to conform to local practices. When you do that
editing, please remember that \fInu\fR runs as root and that the shell
scripts contain statements like ``rm \-rf *''; it goes without saying that
you must be quite cautious. There is a debug mode available, in which
\fInu\fR will try not to hurt anything, but whenever you are running as root
you should be unusually careful. \fINu\fR can be run by non-root users if its
debug mode is enabled by a ``Debug=1'' statement in /etc/nu.cf.
.PP
.SH CONFIGURATION FILE FORMAT
The configuration file /etc/nu.cf is a text file containing a series of
statements, one statement per line. A semicolon that is not inside a quoted
string causes the rest of that line to be treated as a comment. Each line in
the file that is nonblank after stripping comments is treated as an
assignment statement. Each statement assigns a value to one variable. With
the exception of the variable "GroupHome", which is special, all of the
variables act like ordinary shell variables, which is to say that they can
take either integer values or string values. All integers are decimal; all
strings must be delimited with double-quotes ("). There is no quoting or
doubling convention for putting a doublequote character inside a string.
.PP
Here are the configuration variables and what they mean. Case is significant.
.HP 5
.B Backupfile
.br
This string variable gives the pathname that \fInu\fR will use to make a
backup copy of /etc/passwd, to protect itself from disaster in case something
happens while it is writing /etc/passwd. Typical value of Backupfile is
"/usr/adm/nu.passwd".
.HP 5
.B CreateDir
.br
This string  variable identifies the shell script that is run whenever
\fInu\fR needs to create a new directory. That shell script must be
executable. It is called
with 6 arguments: 1, the integer uid; 2, the integer groupid; 3, the name
of the user's actual home directory; 4, the name of a symbolic link that
should be set up to point to that home directory; 5, an integer that is
nonzero iff it is ok to clobber an existing directory of the same name as
argument 4; and 6, an integer that is nonzero iff nu is running in debug
mode. The standard value for CreateDir is "/etc/nulib/nu1.sh".
.HP 5
.B CreateFiles
.br
This string variable identifies the shell script that is run whenever
\fInu\fR needs
to initialize a directory (newly-created or otherwise) with some standard
files. For example, /usr/skel/.[a-z]* are often copied into a new login
directory. This shell script must be executable. It is called with 5
arguments: 1, the name of the login directory to be initialized; 2, the
integer uid of the user; 3, the integer groupid of the user; 4, an integer
that is nonzero iff an MH-format mailbox is to be set up with some initial
contents; and 5, an integer that is nonzero iff \fInu\fR is running in debug
mode. The standard value for CreateFiles is "/etc/nulib/nu2.sh".
.HP 5
.B Debug
.br
This integer variable is set nonzero to cause \fInu\fR to run in debug mode.
Debug mode is intended to help you get the bugs out of your shell scripts
before you go foolishly running them as root. If Debug is nonzero, then you
do not need to be logged on as root to run \fInu\fR. The standard value for
Debug is 0.
.HP 5
.B DefaultGroup
.br
This integer variable is set to the group number of the default user group.
The default is used if the person running \fInu\fR types a carriage return in
response to the question asking for a group id for the new user. \fInu\fR
requires that a valid GroupHome assignment exist for the default group number.
The standard value for DefaultGroup is any group number from /etc/group.
.HP 5
.B DefaultHome
.br
This string variable is set to the file system or top-level directory that
will be used to hold the login directory for accounts in groups 
not explicitly set up to have their login directories somewhere else.
When you are creating a new account, \fInu\fR asks you what group number you
would like the account in. If that group number is mentioned in a GroupHome
declaration (see below), then the home directory for the group is the one
named in that GroupHome declaration. If the group number is not mentioned in
a GroupHome declaration, then login accounts created in that group will have
their login directories put into DefaultHome. The standard value for
DefaultGroup is "/mnt".

.HP 5
.B DefaultShell
.br
This string variable is set to the name of the shell file to use by default.
The standard value for DefaultShell is "/bin/csh".
.HP 5
.B DeleteAccts
.br
This string variable identifies the shell script that is run whenever
\fInu\fR needs to delete a user's account that was created in some earlier
session with \fInu\fR. Deleting accounts involves changing the password so
that the user cannot log in,
deleting all of his files and directories, and deleting his
mailbox. This shell script must be executable. It is called with 5 arguments:
1, the login id of the account to be deleted; 2, the login directory for that
account; 3, the name given in /etc/passwd for the login directory (which
might possibly be a symbolic link to item 2, above, and therefore needs to be
named separately); 4, the name of the log file in which account changes are
being logged, 
and 5, an integer that is nonzero iff \fInu\fR is running in debug mode. The
standard value for DeleteAccts is "/etc/nulib/nu4.sh".
.HP 5
.B DestroyAccts
.br
This string variable identifies the shell script that is run whenever
\fInu\fR needs to destroy a user's account that was created in some earlier
session with \fInu\fR. Destroying accounts involves removing the user from the
password file, deleting all of his files and directories, and deleting his
mailbox. For a (slightly) less drastic account removal action, see
``DeleteAccts'', above.
This shell script must be executable. It is called with 5 arguments:
1, the login id of the account to be deleted; 2, the login directory for that
account; 3, the name given in /etc/passwd for the login directory (which
might possibly be a symbolic link to item 2, above, and therefore needs to be
named separately); 4, the name of the log file in which account changes are
being logged, 
and 5, an integer that is nonzero iff \fInu\fR is running in debug mode. The
standard value for DestroyAccts is "/etc/nulib/nu3.sh".
.HP 5
.B Dummyfile
.br
This string variable holds the name of the hard link that is created as part
of the locking process on /etc/passwd; see \fIvipw(8)\fR. The correct value
for Dummyfile is "/etc/vipw.lock". The only reason that it is specified in
the configuration file and not hardwired into the code of \fInu\fR is that in
debugging you do not want to muck with the real lock (and might in fact not
even have permissions to lock it).
.HP 5
.B GroupHome
.br
This pseudo-variable is the only name defined in the configuration file that
has any trickery attached to it. GroupHome is not really a variable; rather,
it is a name by which the configuration code can load entries into a
directory location table. In particular, if you provide two GroupHome
declarations, they are both processed, while if you provide two of any other
declaration, only the latest one has any effect. A typical set of GroupHome
declarations might look something like this:
.nf
   GroupHome= 10 "/usr"
   GroupHome= 20 "/mnt"
   GroupHome= 25 "/usr/cis"
   GroupHome= 31 "/usr/guest"
.fi
The GroupHome declarations serve as default login directory location
information for new accounts. You can put any account anywhere you want; the
GroupHome information is used to make the defaults come out in the right
places, so that the process of creating a new account consists mostly of
hitting the return key to accept the defaults. The sample declarations above
cause group 10 to default to /usr, i.e. /usr/smith or /usr/jones, and group
31 to default to /usr/guest, i.e. /usr/guest/smith or /usr/guest/jones.
If the login group is not mentioned in a GroupHome declaration, then the
DefaultHome variable is used. A GroupHome declaration is required for the
default group (see variable DefaultGroup); all others are optional.
.HP 5
.B Linkfile
.br
See also ``Dummyfile''. This string variable gives the name of the file to
which links are made for the purpose of locking the password file. Any value
besides "/etc/ptmp" is suspect.
.HP 5
.B Logfile
.br
This string variable names the file in which all \fInu\fR transactions are
logged. The standard value of Logfile is "/usr/adm/nu.log".
.HP 5
.B MaxNameLength
.br
This integer variable gives the maximum number of characters permitted in a
login name. For unmodified 4BSD systems it should be set to 8.
.HP 5
.B PasswdFile
.br
This string variable gives the name of the file into which \fInu\fR will
write its new account entries. Unless you are debugging, its value should be
"/etc/passwd". 
.HP 5
.B SymbolicLinkDir
.br
This string variable gives the name of a directory that can be filled with
symbolic links to real login directories. The value of SymbolicLinkDir is
ignored unless the variable WantSymbolicLinks is nonzero. See its
description, below, for more information. Standard values for SymbolicLinkDir
are "/user" or "/udir".
.HP 5
.B Tempfile
.br
This string variable names the file that \fInu\fR will use for building a
scratch copy of /etc/passwd during the account modification process.
The value doesn't really matter much; it is created at the beginning of an
\fInu\fR execution and destroyed before exit. A typical value for Tempfile is
"/usr/adm/nu.temp".
.HP 5
.B WantMHsetup
.br
This integer variable should be set to 1 if you would like \fInu\fR to take
care of initializing mailbox contents. Initializing an MH mailbox turns out
to be a pleasant way to provide new users with information about the system,
and to give them a tutorial on the use of MH. \fINu\fR just passes the value
of WantMHsetup through to the shell script named in CreateFiles, which is
responsible for doing the actual initialization. Standard value is 1.
.HP 5
.B WantSymbolicLinks
.br
This integer variable controls whether login directory names or symbolic
links to them are put in the actual /etc/passwd file. If WantSymbolicLinks is
nonzero, then all created accounts are given uniform login directory names in
some directory that exists only for the purpose of holding symbolic links,
e.g. /user/smith and /user/jones; the file /user/smith or /user/jones is then
made to be a symbolic link to the real login directory. This is preferable to
the ~smith or ~jones scheme for finding login directories because the ~
notation is not handled by the kernel, but must be handled individually by
all programs that open files. If the variable WantSymbolicLinks is 0, then
accounts will be created such that the true directory name is stored in
/etc/passwd.

.SH SYSTEM ISSUES
\fINu\fR obeys the standard locking protocol for /etc/passwd; see
\fIvipw(8)\fR. It traps INTR characters (e.g. ^C) and refuses to die if you
try to stop it in the middle of a critical section. Critical sections are
primarily the updates of /etc/passwd. A list of all changes is recorded in a
log file, usually /usr/adm/nu.log.

.SH FILES
.ta \w'/usr/adm/nu.passwd    'u
/etc/passwd	system password file
.br
/etc/group	system group file
.br
/etc/ptmp	lock file
.br
/etc/vipw.lock	dummy file linked to by /etc/ptmp
.br
/etc/nu.cf	Configuration file
.br
/etc/nulib/*.sh	Shell scripts to perform the work
.br
others	nu.cf and nulib/*.sh reference other
.br
	files.
.DT
.SH "SEE ALSO"
adduser(8), getgrent(3), getpwent(3), group(5), passwd(5), vipw(8)
.SH AUTHOR
Brian Reid, Erik Hedberg, Fred Yankowski
.SH BUGS
The extensive use of shell scripts for doing sensitive things like purging
accounts means that somebody can make \fInu\fR fail in horrible ways without
having access to the source code. With increased flexibility comes increased
responsibility.
DataMuseum.dk

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