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.\" Generator: DocBook XSL Stylesheets v1.73.2 <http://docbook.sf.net/>
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.\" Manual: System Management Commands
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.\" Source: System Management Commands
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.TH "CHPASSWD" "8" "04/03/2008" "System Management Commands" "System Management Commands"
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.TH "CHPASSWD" "8" "04/15/2009" "System Management Commands" "System Management Commands"
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.\" disable hyphenation
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.\" disable justification (adjust text to left margin only)
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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:
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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:
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\fIuser_name\fR:\fIpassword\fR
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By default the supplied password must be in clear\-text, and is encrypted by
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\fBchpasswd\fR\. Also the password age will be updated, if present\.
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\fBchpasswd\fR\&. Also the password age will be updated, if present\&.
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The default encryption algorithm can be defined for the system with the ENCRYPT_METHOD variable of
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\fI/etc/login\.defs\fR, and can be overwiten with the
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\fI/etc/login\&.defs\fR, and can be overwiten with the
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This command is intended to be used in a large system environment where many accounts are created at a single time\.
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This command is intended to be used in a large system environment where many accounts are created at a single time\&.
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The options which apply to the
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\fB\-c\fR, \fB\-\-crypt\-method\fR
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Use the specified method to encrypt the passwords\.
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Use the specified method to encrypt the passwords\&.
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The available methods are DES, MD5, NONE, and SHA256 or SHA512 if your libc support these methods\.
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The available methods are DES, MD5, NONE, and SHA256 or SHA512 if your libc support these methods\&.
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\fB\-e\fR, \fB\-\-encrypted\fR
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Supplied passwords are in encrypted form\.
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Supplied passwords are in encrypted form\&.
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\fB\-h\fR, \fB\-\-help\fR
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Display help message and exit\.
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Display help message and exit\&.
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\fB\-m\fR, \fB\-\-md5\fR
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Use MD5 encryption instead of DES when the supplied passwords are not encrypted\.
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Use MD5 encryption instead of DES when the supplied passwords are not encrypted\&.
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\fB\-s\fR, \fB\-\-sha\-rounds\fR
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Use the specified number of rounds to encrypt the passwords\.
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The value 0 means that the system will choose the default number of rounds for the crypt method (5000)\.
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A minimal value of 1000 and a maximal value of 999,999,999 will be enforced\.
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You can only use this option with the SHA256 or SHA512 crypt method\.
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Use the specified number of rounds to encrypt the passwords\&.
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The value 0 means that the system will choose the default number of rounds for the crypt method (5000)\&.
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A minimal value of 1000 and a maximal value of 999,999,999 will be enforced\&.
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You can only use this option with the SHA256 or SHA512 crypt method\&.
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By default, the number of rounds is defined by the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
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\fI/etc/login\.defs\fR\.
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\fI/etc/login\&.defs\fR\&.
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Remember to set permissions or umask to prevent readability of unencrypted files by other users\.
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Remember to set permissions or umask to prevent readability of unencrypted files by other users\&.
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PAM is not used to update the passwords\. Only
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PAM is not used to update the passwords\&. Only
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are updated, and the various checks or options provided by PAM modules are not used\.
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are updated, and the various checks or options provided by PAM modules are not used\&.
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.SH "CONFIGURATION"
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The following configuration variables in
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\fI/etc/login\.defs\fR
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\fI/etc/login\&.defs\fR
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change the behavior of this tool:
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\fBENCRYPT_METHOD\fR (string)
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This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line)\.
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This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line)\&.
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It can take one of these values:
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Note: this parameter overrides the
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\fBMD5_CRYPT_ENAB\fR
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Note: if you use PAM, it is recommended to set this variable consistently with the PAM modules configuration\.
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Note: if you use PAM, it is recommended to set this variable consistently with the PAM modules configuration\&.
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\fBMD5_CRYPT_ENAB\fR (boolean)
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Indicate if passwords must be encrypted using the MD5\-based algorithm\. If set to
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\fIyes\fR, new passwords will be encrypted using the MD5\-based algorithm compatible with the one used by recent releases of FreeBSD\. It supports passwords of unlimited length and longer salt strings\. Set to
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Indicate if passwords must be encrypted using the MD5\-based algorithm\&. If set to
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\fIyes\fR, new passwords will be encrypted using the MD5\-based algorithm compatible with the one used by recent releases of FreeBSD\&. It supports passwords of unlimited length and longer salt strings\&. Set to
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if you need to copy encrypted passwords to other systems which don\'t understand the new algorithm\. Default is
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if you need to copy encrypted passwords to other systems which don\'t understand the new algorithm\&. Default is
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This variable is superceded by the
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\fBENCRYPT_METHOD\fR
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variable or by any command line option used to configure the encryption algorithm\.
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This variable is deprecated\. You should use
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\fBENCRYPT_METHOD\fR\.
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Note: if you use PAM, it is recommended to set this variable consistently with the PAM modules configuration\.
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variable or by any command line option used to configure the encryption algorithm\&.
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This variable is deprecated\&. You should use
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\fBENCRYPT_METHOD\fR\&.
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Note: if you use PAM, it is recommended to set this variable consistently with the PAM modules configuration\&.
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\fBSHA_CRYPT_MIN_ROUNDS\fR (number), \fBSHA_CRYPT_MAX_ROUNDS\fR (number)
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\fISHA512\fR, this defines the number of SHA rounds used by the encryption algorithm by default (when the number of rounds is not specified on the command line)\.
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With a lot of rounds, it is more difficult to brute forcing the password\. But note also that more CPU resources will be needed to authenticate users\.
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If not specified, the libc will choose the default number of rounds (5000)\.
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The values must be inside the 1000\-999999999 range\.
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\fISHA512\fR, this defines the number of SHA rounds used by the encryption algorithm by default (when the number of rounds is not specified on the command line)\&.
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With a lot of rounds, it is more difficult to brute forcing the password\&. But note also that more CPU resources will be needed to authenticate users\&.
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If not specified, the libc will choose the default number of rounds (5000)\&.
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The values must be inside the 1000\-999999999 range\&.
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If only one of the
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\fBSHA_CRYPT_MIN_ROUNDS\fR
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\fBSHA_CRYPT_MAX_ROUNDS\fR
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values is set, then this value will be used\.
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values is set, then this value will be used\&.
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\fBSHA_CRYPT_MIN_ROUNDS\fR
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\fBSHA_CRYPT_MAX_ROUNDS\fR, the highest value will be used\.
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\fBSHA_CRYPT_MAX_ROUNDS\fR, the highest value will be used\&.
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\fI/etc/passwd\fR
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User account information\.
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User account information\&.
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\fI/etc/shadow\fR
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Secure user account information\.
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Secure user account information\&.
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\fI/etc/login\.defs\fR
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\fI/etc/login\&.defs\fR
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Shadow password suite configuration\.
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Shadow password suite configuration\&.
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man/chpasswd.8
