201 lines
5.8 KiB
HTML
201 lines
5.8 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SHADOW</TITLE>
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</HEAD><BODY>
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<H1>SHADOW</H1>
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Section: File Formats and Conversions (5)<BR>Updated: 05/28/2020<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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shadow - shadowed password file
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<A NAME="lbAC"> </A>
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<H2>DESCRIPTION</H2>
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<P>
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shadow
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is a file which contains the password information for the system's accounts and optional aging information.
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<P>
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This file must not be readable by regular users if password security is to be maintained.
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<P>
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Each line of this file contains 9 fields, separated by colons (":"), in the following order:
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<P>
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<B>login name</B>
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<DL COMPACT><DT id="1"><DD>
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It must be a valid account name, which exist on the system.
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</DL>
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<P>
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<B>encrypted password</B>
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<DL COMPACT><DT id="2"><DD>
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This field may be empty, in which case no passwords are required to authenticate as the specified login name. However, some applications which read the
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/etc/shadow
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file may decide not to permit any access at all if the password field is empty.
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<P>
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A password field which starts with an exclamation mark means that the password is locked. The remaining characters on the line represent the password field before the password was locked.
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<P>
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Refer to
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<B><A HREF="/cgi-bin/man/man2html?3+crypt">crypt</A></B>(3)
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for details on how this string is interpreted.
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<P>
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If the password field contains some string that is not a valid result of
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<B><A HREF="/cgi-bin/man/man2html?3+crypt">crypt</A></B>(3), for instance ! or *, the user will not be able to use a unix password to log in (but the user may log in the system by other means).
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</DL>
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<P>
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<B>date of last password change</B>
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<DL COMPACT><DT id="3"><DD>
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The date of the last password change, expressed as the number of days since Jan 1, 1970.
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<P>
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The value 0 has a special meaning, which is that the user should change her password the next time she will log in the system.
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<P>
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An empty field means that password aging features are disabled.
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</DL>
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<P>
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<B>minimum password age</B>
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<DL COMPACT><DT id="4"><DD>
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The minimum password age is the number of days the user will have to wait before she will be allowed to change her password again.
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<P>
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An empty field and value 0 mean that there are no minimum password age.
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</DL>
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<P>
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<B>maximum password age</B>
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<DL COMPACT><DT id="5"><DD>
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The maximum password age is the number of days after which the user will have to change her password.
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<P>
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After this number of days is elapsed, the password may still be valid. The user should be asked to change her password the next time she will log in.
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<P>
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An empty field means that there are no maximum password age, no password warning period, and no password inactivity period (see below).
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<P>
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If the maximum password age is lower than the minimum password age, the user cannot change her password.
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</DL>
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<P>
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<B>password warning period</B>
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<DL COMPACT><DT id="6"><DD>
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The number of days before a password is going to expire (see the maximum password age above) during which the user should be warned.
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<P>
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An empty field and value 0 mean that there are no password warning period.
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</DL>
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<P>
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<B>password inactivity period</B>
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<DL COMPACT><DT id="7"><DD>
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The number of days after a password has expired (see the maximum password age above) during which the password should still be accepted (and the user should update her password during the next login).
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<P>
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After expiration of the password and this expiration period is elapsed, no login is possible using the current user's password. The user should contact her administrator.
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<P>
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An empty field means that there are no enforcement of an inactivity period.
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</DL>
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<P>
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<B>account expiration date</B>
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<DL COMPACT><DT id="8"><DD>
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The date of expiration of the account, expressed as the number of days since Jan 1, 1970.
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<P>
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Note that an account expiration differs from a password expiration. In case of an account expiration, the user shall not be allowed to login. In case of a password expiration, the user is not allowed to login using her password.
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<P>
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An empty field means that the account will never expire.
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<P>
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The value 0 should not be used as it is interpreted as either an account with no expiration, or as an expiration on Jan 1, 1970.
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</DL>
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<P>
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<B>reserved field</B>
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<DL COMPACT><DT id="9"><DD>
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This field is reserved for future use.
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</DL>
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<A NAME="lbAD"> </A>
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<H2>FILES</H2>
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<P>
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/etc/passwd
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<DL COMPACT><DT id="10"><DD>
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User account information.
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</DL>
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<P>
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/etc/shadow
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<DL COMPACT><DT id="11"><DD>
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Secure user account information.
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</DL>
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<P>
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/etc/shadow-
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<DL COMPACT><DT id="12"><DD>
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Backup file for /etc/shadow.
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<P>
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Note that this file is used by the tools of the shadow toolsuite, but not by all user and password management tools.
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</DL>
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<A NAME="lbAE"> </A>
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<H2>SEE ALSO</H2>
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<P>
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<B><A HREF="/cgi-bin/man/man2html?1+chage">chage</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+login">login</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+passwd">passwd</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?5+passwd">passwd</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?8+pwck">pwck</A></B>(8),
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<B><A HREF="/cgi-bin/man/man2html?8+pwconv">pwconv</A></B>(8),
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<B><A HREF="/cgi-bin/man/man2html?8+pwunconv">pwunconv</A></B>(8),
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<B><A HREF="/cgi-bin/man/man2html?1+su">su</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?8+sulogin">sulogin</A></B>(8).
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="13"><A HREF="#lbAB">NAME</A><DD>
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<DT id="14"><A HREF="#lbAC">DESCRIPTION</A><DD>
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<DT id="15"><A HREF="#lbAD">FILES</A><DD>
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<DT id="16"><A HREF="#lbAE">SEE ALSO</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:05 GMT, March 31, 2021
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</BODY>
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</HTML>
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