405 lines
12 KiB
XML
405 lines
12 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<refentry id='passwd.1'>
|
|
<!-- $Id$ -->
|
|
<refmeta>
|
|
<refentrytitle>passwd</refentrytitle>
|
|
<manvolnum>1</manvolnum>
|
|
<refmiscinfo class="sectdesc">User Commands</refmiscinfo>
|
|
</refmeta>
|
|
<refnamediv id='name'>
|
|
<refname>passwd</refname>
|
|
<refpurpose>change user password</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv id='synopsis'>
|
|
<cmdsynopsis>
|
|
<command>passwd</command>
|
|
<arg choice='opt'>
|
|
<replaceable>options</replaceable>
|
|
</arg>
|
|
<arg choice='opt'>
|
|
<replaceable>LOGIN</replaceable>
|
|
</arg>
|
|
</cmdsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1 id='description'>
|
|
<title>DESCRIPTION</title>
|
|
<para>
|
|
The <command>passwd</command> command changes passwords for user accounts.
|
|
A normal user may only change the password for his/her own account, while
|
|
the superuser may change the password for any account.
|
|
<command>passwd</command> also changes account information, such as
|
|
the full name of the user, the user's login shell, or his/her password
|
|
expiry date and interval.
|
|
</para>
|
|
|
|
<refsect2 id='password_changes'>
|
|
<title>Password Changes</title>
|
|
<para>
|
|
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 superuser is permitted to bypass this step so that
|
|
forgotten passwords may be changed.
|
|
</para>
|
|
|
|
<para>
|
|
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, <command>passwd</command> refuses to change the
|
|
password and exits.
|
|
</para>
|
|
|
|
<para>
|
|
The user is then prompted twice for a replacement password. The
|
|
second entry is compared against the first and both are required to
|
|
match in order for the password to be changed.
|
|
</para>
|
|
|
|
<para>
|
|
Then, the password is tested for complexity. As a general guideline,
|
|
passwords should consist of 6 to 8 characters including one or more
|
|
characters from each of the following sets:
|
|
</para>
|
|
|
|
<itemizedlist mark='bullet'>
|
|
<listitem>
|
|
<para>lower case alphabetics</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>digits 0 thru 9</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>punctuation marks</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>
|
|
Care must be taken not to include the system default erase or kill
|
|
characters. <command>passwd</command> will reject any password which
|
|
is not suitably complex.
|
|
</para>
|
|
|
|
</refsect2>
|
|
|
|
<refsect2 id='hints_for_user_passwords'>
|
|
<title>Hints for user passwords</title>
|
|
<para>
|
|
The security of a password depends upon the strength of the
|
|
encryption algorithm and the size of the key space. The
|
|
<emphasis>UNIX</emphasis> 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.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<para>
|
|
Your password must be 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.
|
|
</para>
|
|
|
|
<para>
|
|
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:
|
|
</para>
|
|
|
|
<itemizedlist mark='bullet'>
|
|
<listitem>
|
|
<para>Ask not for whom the bell tolls</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>which produces</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>An4wtbt</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1 id='options'>
|
|
<title>OPTIONS</title>
|
|
<para>
|
|
The options which apply to the <command>passwd</command> command are:
|
|
</para>
|
|
<variablelist remap='IP'>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-a</option>, <option>--all</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
This option can be used only with <option>-S</option> and causes show
|
|
status for all users.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-d</option>, <option>--delete</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Delete a user's password (make it empty). This is a quick way
|
|
to disable a password for an account. It will set the named
|
|
account passwordless.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-e</option>, <option>--expire</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Immediately expire an account's password. This in effect can
|
|
force a user to change his/her password at the user's next login.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><option>-h</option>, <option>--help</option></term>
|
|
<listitem>
|
|
<para>Display help message and exit.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-i</option>, <option>--inactive</option> <replaceable>INACTIVE</replaceable>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
This 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 <replaceable>INACTIVE</replaceable>
|
|
days, the user may no longer sign on to the account.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-k</option>, <option>--keep-tokens</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Indicate password change should be performed only for expired
|
|
authentication tokens (passwords). The user wishes to keep their
|
|
non-expired tokens as before.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-l</option>, <option>--lock</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Lock the named account. This option disables an account by changing
|
|
the password to a value which matches no possible encrypted value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-m</option>, <option>--mindays</option> <replaceable>MIN_DAYS</replaceable>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Set the minimum number of days between password changes to
|
|
<replaceable>MIN_DAYS</replaceable>. A value of zero for this field
|
|
indicates that the user may change his/her password at any time.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-q</option>, <option>--quiet</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Quiet mode.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-r</option>, <option>--repository</option> <replaceable>REPOSITORY</replaceable>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
change password in <replaceable>REPOSITORY</replaceable> repository
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-S</option>, <option>--status</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Display account status information. 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.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-u</option>, <option>--unlock</option>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Unlock the named account. This option re-enables an account by
|
|
changing the password back to its previous value (to value before
|
|
using <option>-l</option> option).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-w</option>, <option>--warndays</option> <replaceable>WARN_DAYS</replaceable>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Set the number of days of warning before a password change is
|
|
required. The <replaceable>WARN_DAYS</replaceable> option is
|
|
the number of days prior to the password expiring that a user
|
|
will be warned that his/her password is about to expire.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>
|
|
<option>-x</option>, <option>--maxdays</option> <replaceable>MAX_DAYS</replaceable>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Set the maximum number of days a password remains valid. After
|
|
<replaceable>MAX_DAYS</replaceable>, the password is required
|
|
to be changed.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1 id='caveats'>
|
|
<title>CAVEATS</title>
|
|
<para>
|
|
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 or she 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.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 id='files'>
|
|
<title>FILES</title>
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>/etc/passwd</filename></term>
|
|
<listitem>
|
|
<para>User account information.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>/etc/shadow</filename></term>
|
|
<listitem>
|
|
<para>Secure user account information.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1 id='exit_values'>
|
|
<title>EXIT VALUES</title>
|
|
<para>
|
|
The <command>passwd</command> command exits with the following values:
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable>0</replaceable></term>
|
|
<listitem>
|
|
<para>success</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>1</replaceable></term>
|
|
<listitem>
|
|
<para>permission denied</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>2</replaceable></term>
|
|
<listitem>
|
|
<para>invalid combination of options</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>3</replaceable></term>
|
|
<listitem>
|
|
<para>unexpected failure, nothing done</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>4</replaceable></term>
|
|
<listitem>
|
|
<para>unexpected failure, <filename>passwd</filename> file missing</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>5</replaceable></term>
|
|
<listitem>
|
|
<para><filename>passwd</filename> file busy, try again</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><replaceable>6</replaceable></term>
|
|
<listitem>
|
|
<para>invalid argument to option</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 id='see_also'>
|
|
<title>SEE ALSO</title>
|
|
<para>
|
|
<citerefentry>
|
|
<refentrytitle>group</refentrytitle><manvolnum>5</manvolnum>
|
|
</citerefentry>,
|
|
<citerefentry>
|
|
<refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum>
|
|
</citerefentry>,
|
|
<citerefentry>
|
|
<refentrytitle>shadow</refentrytitle><manvolnum>5</manvolnum>
|
|
</citerefentry>.
|
|
</para>
|
|
</refsect1>
|
|
</refentry>
|