199 lines
9.0 KiB
Groff
199 lines
9.0 KiB
Groff
.\" $Id: passwd.1,v 1.25 2005/05/09 10:14:40 kloczek Exp $
|
|
.\" Copyright 1989 - 1994, Julianne Frances Haugh
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of Julianne F. Haugh nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.TH PASSWD 1
|
|
.SH NAME
|
|
passwd \- change user password
|
|
.SH SYNOPSIS
|
|
\fBpasswd\fR [\fB\-f\fR|\fB\-s\fR] [\fIname\fR]
|
|
.br
|
|
\fBpasswd\fR [\fB\-g\fR] [\fB\-r\fR|\fB\-R\fR] \fIgroup\fR
|
|
.br
|
|
\fBpasswd\fR [\fB\-x\fR \fImax\fR] [\fB\-n\fR \fImin\fR]
|
|
[\fB\-w\fR \fIwarn\fR] [\fB\-i\fR \fIinact\fR] \fIlogin\fR
|
|
.br
|
|
\fBpasswd\fR {\fB\-l\fR|\fB\-u\fR|\fB\-d\fR|\fB\-S\fR|\fB\-e\fR} \fIlogin\fR
|
|
.SH DESCRIPTION
|
|
\fBpasswd\fR changes passwords for user and group accounts. A normal user
|
|
may only change the password for his/her own account, the super user may
|
|
change the password for any account. The administrator of a group may change
|
|
the password for the group. \fBpasswd\fR also changes account information,
|
|
such as the full name of the user, user's login shell, or password expiry
|
|
date and interval.
|
|
.PP
|
|
The \fB\-s\fR option makes \fBpasswd\fR call \fBchsh\fR to change the user's
|
|
shell. The \fB\-f\fR option makes \fBpasswd\fR call \fBchfn\fR to change the user's
|
|
gecos information. These two options are only meant for compatiblity, since
|
|
the other programs can be called directly.
|
|
.SS Password Changes
|
|
The user is first prompted for his/her old password, if one is present. This
|
|
password is then encrypted and compared against the stored password. The
|
|
user has only one chance to enter the correct password. The super user is
|
|
permitted to bypass this step so that forgotten passwords may be changed.
|
|
.PP
|
|
After the password has been entered, password aging information is checked
|
|
to see if the user is permitted to change the password at this time. If not,
|
|
\fBpasswd\fR refuses to change the password and exits.
|
|
.PP
|
|
The user is then prompted for a replacement password. This password is
|
|
tested for complexity. As a general guideline, passwords should consist of 6
|
|
to 8 characters including one or more from each of following sets:
|
|
.IP "" .5i
|
|
Lower case alphabetics
|
|
.IP "" .5i
|
|
Upper case alphabetics
|
|
.IP "" .5i
|
|
Digits 0 thru 9
|
|
.IP "" .5i
|
|
Punctuation marks
|
|
.PP
|
|
Care must be taken not to include the system default erase or kill
|
|
characters. \fBpasswd\fR will reject any password which is not suitably
|
|
complex.
|
|
.PP
|
|
If the password is accepted, \fBpasswd\fR will prompt again and compare the
|
|
second entry against the first. Both entries are required to match in order
|
|
for the password to be changed.
|
|
.SS Group passwords
|
|
When the \fB\-g\fR option is used, the password for the named group is
|
|
changed. The user must either be the super user, or a group administrator
|
|
for the named group. The current group password is not prompted for. The
|
|
\fB\-r\fR option is used with the \fB\-g\fR option to remove the current
|
|
password from the named group. This allows group access to all members. The
|
|
\fB\-R\fR option is used with the \fB\-g\fR option to restrict the named group
|
|
for all users.
|
|
.SS Password expiry information
|
|
The password aging information may be changed by the super user with the
|
|
\fB\-x\fR, \fB\-n\fR, \fB\-w\fR, and \fB\-i\fR options. The \fB\-x\fR option is
|
|
used to set the maximum number of days a password remains valid. After
|
|
\fImax\fR days, the password is required to be changed. The \fB\-n\fR option
|
|
is used to set the minimum number of days before a password may be changed.
|
|
The user will not be permitted to change the password until \fImin\fR days
|
|
have elapsed. The \fB\-w\fR option is used to set the number of days of
|
|
warning the user will receive before his/her password will expire. The
|
|
warning occurs \fIwarn\fR days before the expiration, telling the user how
|
|
many days remain until the password is set to expire. The \fB\-i\fR option is
|
|
used to disable an account after the password has been expired for a number
|
|
of days. After a user account has had an expired password for \fIinact\fR
|
|
days, the user may no longer sign on to the account.
|
|
.PP
|
|
If you wish to immediately expire an account's password, you can use the
|
|
\fB\-e\fR option. This in effect can force a user to change his/her password at
|
|
the user's next login. You can also use the \fB\-d\fR option to delete a user's
|
|
password (make it empty). Use caution with this option since it can make an
|
|
account not require a password at all to login, leaving your system open to
|
|
intruders.
|
|
.SS Account maintenance
|
|
User accounts may be locked and unlocked with the \fB\-l\fR and \fB\-u\fR
|
|
flags. The \fB\-l\fR option disables an account by changing the password to
|
|
a value which matches no possible encrypted value. The \fB\-u\fR option
|
|
re\-enables an account by changing the password back to its previous value.
|
|
.PP
|
|
The account status may be viewed with the \fB-S\fR option.
|
|
The status information consists of 7 fields.
|
|
The first field is the user's login name.
|
|
The second field indicates if the user account is locked (L), has no
|
|
password (NP), or has a usable password (P).
|
|
The third field gives the date of the last password change.
|
|
The next four fields are the minimum age, maximum age, warning period,
|
|
and inactivity period for the password.
|
|
These ages are expressed in days.
|
|
See \fBPassword expiry information\fR above for a discussion of these fields.
|
|
.SS Hints for user passwords
|
|
The security of a password depends upon the strength of the
|
|
encryption algorithm and the size of the key space.
|
|
The \fB\s\-2UNIX\s+2\fR System encryption method is based on
|
|
the NBS DES algorithm and is very secure.
|
|
The size of the key space depends upon the randomness of the
|
|
password which is selected.
|
|
.PP
|
|
Compromises in password security normally result from careless
|
|
password selection or handling.
|
|
For this reason, you should not select a password which appears in
|
|
a dictionary or which must be written down.
|
|
The password should also not be a proper name, your license
|
|
number, birth date, or street address.
|
|
Any of these may be used as guesses to violate system security.
|
|
.PP
|
|
Your password must easily remembered so that you will not
|
|
be forced to write it on a piece of paper.
|
|
This can be accomplished by appending two small words together
|
|
and separating each with a special character or digit.
|
|
For example, Pass%word.
|
|
.PP
|
|
Other methods of construction involve selecting an easily
|
|
remembered phrase from literature and selecting the first
|
|
or last letter from each word.
|
|
An example of this is
|
|
.IP "" .5i
|
|
Ask not for whom the bell tolls.
|
|
.PP
|
|
which produces
|
|
.IP "" .5i
|
|
An4wtbt.
|
|
.PP
|
|
You may be reasonably sure few crackers will have included this in their
|
|
dictionaries. You should, however, select your own methods for constructing
|
|
passwords and not rely exclusively on the methods given here.
|
|
.SS Notes about group passwords
|
|
Group passwords are an inherent security problem since more than one person
|
|
is permitted to know the password. However, groups are a useful tool for
|
|
permitting co\-operation between different users.
|
|
.SH CAVEATS
|
|
Not all options may be supported.
|
|
Password complexity checking may vary from site to site.
|
|
The user is urged to select a password as complex as he
|
|
feels comfortable with.
|
|
Users may not be able to change their password on a system if NIS
|
|
is enabled and they are not logged into the NIS server.
|
|
.SH FILES
|
|
\fI/etc/passwd\fR \- user account information
|
|
.br
|
|
\fI/etc/shadow\fR \- secure user account information
|
|
.SH EXIT VALUES
|
|
.TP 2
|
|
The \fBpasswd\fR command exits with the following values:
|
|
\fB0\fR \- success
|
|
.br
|
|
\fB1\fR \- permission denied
|
|
.br
|
|
\fB2\fR \- invalid combination of options
|
|
.br
|
|
\fB3\fR \- unexpected failure, nothing done
|
|
.br
|
|
\fB4\fR \- unexpected failure, passwd file missing
|
|
.br
|
|
\fB5\fR \- passwd file busy, try again later
|
|
.br
|
|
\fB6\fR \- invalid argument to option
|
|
.SH "SEE ALSO"
|
|
.BR group (5),
|
|
.BR passwd (5),
|
|
.BR shadow (5)
|
|
.SH AUTHOR
|
|
Julianne Frances Haugh <jockgrrl@ix.netcom.com>
|