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chpasswd.8.xml
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chpasswd.8.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!--
SPDX-FileCopyrightText: 1991 , Julianne Frances Haugh
SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
SPDX-License-Identifier: BSD-3-Clause
-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
"http:https://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY BCRYPT_MIN_ROUNDS SYSTEM "login.defs.d/BCRYPT_MIN_ROUNDS.xml">
<!ENTITY ENCRYPT_METHOD SYSTEM "login.defs.d/ENCRYPT_METHOD.xml">
<!ENTITY MD5_CRYPT_ENAB SYSTEM "login.defs.d/MD5_CRYPT_ENAB.xml">
<!ENTITY SHA_CRYPT_MIN_ROUNDS SYSTEM "login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml">
<!ENTITY YESCRYPT_COST_FACTOR SYSTEM "login.defs.d/YESCRYPT_COST_FACTOR.xml">
<!-- SHADOW-CONFIG-HERE -->
]>
<refentry id='chpasswd.8'>
<!-- $Id$ -->
<refentryinfo>
<author>
<firstname>Julianne Frances</firstname>
<surname>Haugh</surname>
<contrib>Creation, 1991</contrib>
</author>
<author>
<firstname>Thomas</firstname>
<surname>Kłoczko</surname>
<email>[email protected]</email>
<contrib>shadow-utils maintainer, 2000 - 2007</contrib>
</author>
<author>
<firstname>Nicolas</firstname>
<surname>François</surname>
<email>[email protected]</email>
<contrib>shadow-utils maintainer, 2007 - now</contrib>
</author>
</refentryinfo>
<refmeta>
<refentrytitle>chpasswd</refentrytitle>
<manvolnum>8</manvolnum>
<refmiscinfo class="sectdesc">System Management Commands</refmiscinfo>
<refmiscinfo class="source">shadow-utils</refmiscinfo>
<refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>chpasswd</refname>
<refpurpose>update passwords in batch mode</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>
<cmdsynopsis>
<command>chpasswd</command>
<arg choice='opt'>
<replaceable>options</replaceable>
</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id='description'>
<title>DESCRIPTION</title>
<para>
The <command>chpasswd</command> command reads a list of user name and
password pairs from standard input and uses this information to update
a group of existing users. Each line is of the format:
</para>
<para>
<emphasis remap='I'>user_name</emphasis>:<emphasis
remap='I'>password</emphasis>
</para>
<para>
By default the passwords must be supplied in clear-text, and are
encrypted by <command>chpasswd</command>.
Also the password age will be updated, if present.
</para>
<para condition="no_pam">
The default encryption algorithm can be defined for the system with
the <option>ENCRYPT_METHOD</option> or
<option>MD5_CRYPT_ENAB</option> variables of
<filename>/etc/login.defs</filename>, and can be overwritten with the
<option>-e</option>, <option>-m</option>, or <option>-c</option>
options.
</para>
<para condition="pam">
By default, passwords are encrypted by PAM, but (even if not
recommended) you can select a different encryption method with the
<option>-e</option>, <option>-m</option>, or <option>-c</option>
options.
</para>
<para>
<phrase condition="pam">Except when PAM is used to encrypt the
passwords,</phrase> <command>chpasswd</command> first updates all the
passwords in memory, and then commits all the changes to disk if no
errors occurred for any user.
</para>
<para condition="pam">
When PAM is used to encrypt the passwords (and update the passwords in
the system database) then if a password cannot be updated
<command>chpasswd</command> continues updating the passwords of the
next users, and will return an error code on exit.
</para>
<para>
This command is intended to be used in a large system environment
where many accounts are created at a single time.
</para>
</refsect1>
<refsect1 id='options'>
<title>OPTIONS</title>
<para>
The options which apply to the <command>chpasswd</command> command
are:
</para>
<variablelist remap='IP'>
<varlistentry>
<term>
<option>-c</option>, <option>--crypt-method</option> <replaceable>METHOD</replaceable>
</term>
<listitem>
<para>Use the specified method to encrypt the passwords.</para>
<para>
The available methods are <phrase condition="bcrypt">
<replaceable>BCRYPT</replaceable>,</phrase>
<replaceable>DES</replaceable>,
<replaceable>MD5</replaceable><phrase condition="sha_crypt">,
<replaceable>SHA256</replaceable>,
<replaceable>SHA512</replaceable></phrase><phrase condition="yescrypt">,
<replaceable>YESCRYPT</replaceable></phrase> and
<replaceable>NONE</replaceable>
if your libc supports these methods.
</para>
<para condition="pam">
By default, PAM is used to encrypt the passwords.
</para>
<para condition="no_pam">
By default (if none of the <option>-c</option>,
<option>-m</option>, or <option>-e</option> options are
specified), the encryption method is defined by the
<option>ENCRYPT_METHOD</option> or
<option>MD5_CRYPT_ENAB</option> variables of
<filename>/etc/login.defs</filename>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-e</option>, <option>--encrypted</option></term>
<listitem>
<para>Supplied passwords are in encrypted form.</para>
</listitem>
</varlistentry>
</variablelist>
<variablelist remap='IP'>
<varlistentry>
<term><option>-h</option>, <option>--help</option></term>
<listitem>
<para>Display help message and exit.</para>
</listitem>
</varlistentry>
</variablelist>
<variablelist remap='IP'>
<varlistentry>
<term><option>-m</option>, <option>--md5</option></term>
<listitem>
<para>
Use MD5 encryption instead of DES when the supplied passwords are
not encrypted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-R</option>, <option>--root</option> <replaceable>CHROOT_DIR</replaceable>
</term>
<listitem>
<para>
Apply changes in the <replaceable>CHROOT_DIR</replaceable>
directory and use the configuration files from the
<replaceable>CHROOT_DIR</replaceable> directory.
Only absolute paths are supported.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>-P</option>, <option>--prefix</option> <replaceable>PREFIX_DIR</replaceable>
</term>
<listitem>
<para>
Apply changes to configuration files under the root filesystem
found under the directory <replaceable>PREFIX_DIR</replaceable>.
This option does not chroot and is intended for preparing a cross-compilation
target. Some limitations: NIS and LDAP users/groups are
not verified. PAM authentication is using the host files.
No SELINUX support.
</para>
</listitem>
</varlistentry>
<varlistentry condition="bcrypt;sha_crypt;yescrypt">
<term>
<option>-s</option>, <option>--sha-rounds</option> <replaceable>ROUNDS</replaceable>
</term>
<listitem>
<para>
Use the specified number of rounds to encrypt the passwords.
</para>
<para>
You can only use this option with crypt method:
<phrase condition="bcrypt">
<replaceable>BCRYPT</replaceable></phrase>
<phrase condition="sha_crypt">
<replaceable>SHA256</replaceable>
<replaceable>SHA512</replaceable></phrase>
<phrase condition="yescrypt">
<replaceable>YESCRYPT</replaceable></phrase>
</para>
<para condition="bcrypt">
By default, the number of rounds for BCRYPT is defined by the
BCRYPT_MIN_ROUNDS and BCRYPT_MAX_ROUNDS variables in
<filename>/etc/login.defs</filename>.
</para>
<para condition="bcrypt">
A minimal value of 4 and a maximal value of 31
will be enforced for BCRYPT. The default number of rounds is 13.
</para>
<para condition="sha_crypt">
By default, the number of rounds for SHA256 or SHA512 is defined by
the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
<filename>/etc/login.defs</filename>.
</para>
<para condition="sha_crypt">
A minimal value of 1000 and a maximal value of 999,999,999
will be enforced for SHA256 and SHA512. The default number of rounds
is 5000.
</para>
<para condition="yescrypt">
By default, the number of rounds for YESCRYPT is defined by the
YESCRYPT_COST_FACTOR in <filename>/etc/login.defs</filename>.
</para>
<para condition="yescrypt">
A minimal value of 1 and a maximal value of 11
will be enforced for YESCRYPT. The default number of rounds is 5.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id='caveats'>
<title>CAVEATS</title>
<para>
Remember to set permissions or umask to prevent readability of
unencrypted files by other users.
</para>
</refsect1>
<refsect1 id='configuration'>
<title>CONFIGURATION</title>
<para>
The following configuration variables in
<filename>/etc/login.defs</filename> change the behavior of this
tool:
</para>
<variablelist condition="no_pam">
&ENCRYPT_METHOD;
&MD5_CRYPT_ENAB;
</variablelist>
<variablelist>
&BCRYPT_MIN_ROUNDS; <!--documents also BCRYPT_MAX_ROUNDS-->
&SHA_CRYPT_MIN_ROUNDS; <!--documents also SHA_CRYPT_MAX_ROUNDS-->
&YESCRYPT_COST_FACTOR;
</variablelist>
</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>
<varlistentry>
<term><filename>/etc/login.defs</filename></term>
<listitem>
<para>Shadow password suite configuration.</para>
</listitem>
</varlistentry>
<varlistentry condition="pam">
<term><filename>/etc/pam.d/chpasswd</filename></term>
<listitem>
<para>PAM configuration for <command>chpasswd</command>.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id='see_also'>
<title>SEE ALSO</title>
<para>
<citerefentry>
<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>newusers</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>,
<phrase>
<citerefentry>
<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
</phrase>
<citerefentry>
<refentrytitle>useradd</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>.
</para>
</refsect1>
</refentry>