289 lines
8.9 KiB
XML
289 lines
8.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<refentry id='chpasswd.8'>
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<!-- $Id$ -->
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<refmeta>
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<refentrytitle>chpasswd</refentrytitle>
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<manvolnum>8</manvolnum>
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<refmiscinfo class="sectdesc">System Management Commands</refmiscinfo>
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</refmeta>
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<refnamediv id='name'>
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<refname>chpasswd</refname>
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<refpurpose>update passwords in batch mode</refpurpose>
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</refnamediv>
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<refsynopsisdiv id='synopsis'>
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<cmdsynopsis>
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<command>chpasswd</command>
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<arg choice='opt'>
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<replaceable>options</replaceable>
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</arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1 id='description'>
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<title>DESCRIPTION</title>
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<para>
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The <command>chpasswd</command> command reads a list of user name and
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password pairs from standard input and uses this information to update
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a group of existing users. Each line is of the format:
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</para>
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<para>
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<emphasis remap='I'>user_name</emphasis>:<emphasis
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remap='I'>password</emphasis>
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</para>
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<para>
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By default the supplied password must be in clear-text, and is
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encrypted by <command>chpasswd</command>.
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Also the password age will be updated, if present.
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</para>
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<para>
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The default encryption algorithm can be defined for the system with
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the ENCRYPT_METHOD variable of <filename>/etc/login.defs</filename>,
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and can be overwiten with the <option>-e</option>,
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<option>-m</option>, or <option>-c</option> options.
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</para>
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<para>
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This command is intended to be used in a large system environment
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where many accounts are created at a single time.
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</para>
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</refsect1>
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<refsect1 id='options'>
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<title>OPTIONS</title>
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<para>
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The options which apply to the <command>chpasswd</command> command
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are:
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</para>
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<variablelist remap='IP'>
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<varlistentry>
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<term><option>-c</option>, <option>--crypt-method</option></term>
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<listitem>
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<para>Use the specified method to encrypt the passwords.</para>
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<para>
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The available methods are DES, MD5, and SHA256 or SHA512
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if compiled with the ENCRYPTMETHOD_SELECT flag.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-e</option>, <option>--encrypted</option></term>
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<listitem>
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<para>Supplied passwords are in encrypted form.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-h</option>, <option>--help</option></term>
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<listitem>
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<para>Display help message and exit.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-m</option>, <option>--md5</option></term>
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<listitem>
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<para>
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Use MD5 encryption instead of DES when the supplied passwords are
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not encrypted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-s</option>, <option>--sha-rounds</option></term>
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<listitem>
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<para>
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Use the specified number of rounds to encrypt the passwords.
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</para>
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<para>
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The value 0 means that the system will choose the default
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number of rounds for the crypt method (5000).
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</para>
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<para>
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A minimal value of 1000 and a maximal value of 999,999,999
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will be enforced.
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</para>
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<para>
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You can only use this option with the SHA256 or SHA512
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crypt method.
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</para>
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<para>
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By default, the number of rounds is defined by the
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SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
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<filename>/etc/login.defs</filename>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id='caveats'>
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<title>CAVEATS</title>
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<para>
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Remember to set permissions or umask to prevent readability of
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unencrypted files by other users.
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</para>
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<para>
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PAM is not used to update the passwords.
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Only <filename>/etc/passwd</filename> and
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<filename>/etc/shadow</filename> are updated, and the various checks
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or options provided by PAM modules are not used.
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</para>
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</refsect1>
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<refsect1 id='configuration'>
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<title>CONFIGURATION</title>
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<para>
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The following configuration variables in
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<filename>/etc/login.defs</filename> change the behavior of this
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tool:
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</para>
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<!--********************************************************************
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** **
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** Definitions copied from login.def.5.xml **
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** **
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********************************************************************-->
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<variablelist>
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<varlistentry>
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<term><option>MD5_CRYPT_ENAB</option> (boolean)</term>
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<listitem>
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<para>
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Indicate if passwords must be encrypted using the MD5-based
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algorithm. If set to <replaceable>yes</replaceable>, new
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passwords will be encrypted
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using the MD5-based algorithm compatible with the one used by
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recent releases of FreeBSD. It supports passwords of
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unlimited length and longer salt strings. Set to
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<replaceable>no</replaceable> if you
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need to copy encrypted passwords to other systems which don't
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understand the new algorithm. Default is
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<replaceable>no</replaceable>.
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</para>
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<para>
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This variable is superceded by the
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<option>ENCRYPT_METHOD</option> variable or by any command
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line option.
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</para>
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<para>
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This variable is deprecated. You should use
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<option>ENCRYPT_METHOD</option>.
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</para>
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<para>
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Note: if you use PAM, it is recommended to set this variable
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consistently with the PAM modules configuration.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ENCRYPT_METHOD</option> (string)</term>
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<listitem>
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<para>
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This defines the system default encryption algorithm for
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encrypting passwords (if no algorithm are specified on the
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command line).
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</para>
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<para>
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It can take one of these values:
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<itemizedlist>
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<listitem>
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<para><replaceable>DES</replaceable> (default)</para>
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</listitem>
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<listitem>
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<para><replaceable>MD5</replaceable></para>
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</listitem>
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<listitem>
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<para><replaceable>SHA256</replaceable></para>
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</listitem>
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<listitem>
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<para><replaceable>SHA512</replaceable></para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Note: this parameter overrides the
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<option>MD5_CRYPT_ENAB</option> variable.
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</para>
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<para>
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Note: if you use PAM, it is recommended to set this variable
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consistently with the PAM modules configuration.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>SHA_CRYPT_MIN_ROUNDS</option> (number)</term>
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<term><option>SHA_CRYPT_MAX_ROUNDS</option> (number)</term>
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<listitem>
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<para>
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When <option>ENCRYPT_METHOD</option> is set to
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<replaceable>SHA256</replaceable> or
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<replaceable>SHA512</replaceable>, this defines the number of
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SHA rounds used by the encryption algorithm by default (when
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the number of rounds is not specified on the command line).
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</para>
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<para>
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With a lot of rounds, it is more difficult to brute forcing
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the password. But note also that more CPU resources will be
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needed to authenticate users.
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</para>
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<para>
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If not specified, the libc will choose the default number of
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rounds (5000).
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</para>
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<para>
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The values must be inside the 1000-999999999 range.
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</para>
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<para>
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If only one of the <option>SHA_CRYPT_MIN_ROUNDS</option> or
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<option>SHA_CRYPT_MAX_ROUNDS</option> values is set, then this
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value will be used.
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</para>
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<para>
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If <option>SHA_CRYPT_MIN_ROUNDS</option> >
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<option>SHA_CRYPT_MAX_ROUNDS</option>, the highest value will
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be used.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id='files'>
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<title>FILES</title>
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<variablelist>
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<varlistentry>
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<term><filename>/etc/passwd</filename></term>
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<listitem>
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<para>User account information.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>/etc/shadow</filename></term>
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<listitem>
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<para>Secure user account information.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>/etc/login.defs</filename></term>
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<listitem>
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<para>Shadow password suite configuration.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id='see_also'>
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<title>SEE ALSO</title>
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<para>
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<citerefentry>
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<refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>newusers</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>useradd</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry>.
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</para>
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</refsect1>
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</refentry>
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