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'\" t
.\" Title: chpasswd
.\" Author: Julianne Frances Haugh
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\" Date: 01.02.2026
.\" Manual: System Management Commands
.\" Source: shadow-utils 4.19.3
.\" Language: German
.\"
.TH "CHPASSWD" "8" "01.02.2026" "shadow\-utils 4\&.19\&.3" "System Management Commands"
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.SH "NAME"
chpasswd \- aktualisiert Passw\(:orter im Stapel\-Modus
.SH "\(:UBERSICHT"
.HP \w'\fBchpasswd\fR\ 'u
\fBchpasswd\fR [\fIoptions\fR]
.SH "BESCHREIBUNG"
.PP
The
\fBchpasswd\fR
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:
.PP
\fIuser_name\fR:\fIpassword\fR
.PP
By default the passwords must be supplied in clear\-text, and are encrypted by
\fBchpasswd\fR\&. Also the password age will be updated, if present\&.
.PP
The default encryption algorithm can be defined for the system with the
\fBENCRYPT_METHOD\fR
or
\fBMD5_CRYPT_ENAB\fR
variables of
/etc/login\&.defs, and can be overwritten with the
\fB\-e\fR,
\fB\-m\fR, or
\fB\-c\fR
options\&.
.PP
\fBchpasswd\fR
first updates all the passwords in memory, and then commits all the changes to disk if no errors occurred for any user\&.
.PP
Dieser Befehl ist f\(:ur weitreichende Systeme gedacht, bei denenviele Passw\(:orter gleichzeitig aktualisiert werden m\(:ussen\&.
.SH "OPTIONEN"
.PP
The options which apply to the
\fBchpasswd\fR
command are:
.PP
\fB\-c\fR, \fB\-\-crypt\-method\fR\ \&\fIMETHOD\fR
.RS 4
definiert die Methode, mit der die Passw\(:orter verschl\(:usselt werden\&.
.sp
The available methods are
\fIDES\fR,
\fIMD5\fR, \fISHA256\fR, \fISHA512\fR
and
\fINONE\fR
if your libc supports these methods\&.
.sp
By default (if none of the
\fB\-c\fR,
\fB\-m\fR, or
\fB\-e\fR
options are specified), the encryption method is defined by the
\fBENCRYPT_METHOD\fR
or
\fBMD5_CRYPT_ENAB\fR
variables of
/etc/login\&.defs\&.
.RE
.PP
\fB\-e\fR, \fB\-\-encrypted\fR
.RS 4
Passw\(:orter werden verschl\(:usselt geliefert\&.
.RE
.PP
\fB\-h\fR, \fB\-\-help\fR
.RS 4
zeigt die Hilfe an und beendet das Programm\&.
.RE
.PP
\fB\-m\fR, \fB\-\-md5\fR
.RS 4
Zur Verschl\(:usselung MD5 anstelle von DES verwenden, wenn die Passw\(:orter unverschl\(:usselt geliefert werden\&.
.RE
.PP
\fB\-R\fR, \fB\-\-root\fR\ \&\fICHROOT_DIR\fR
.RS 4
Apply changes in the
\fICHROOT_DIR\fR
directory and use the configuration files from the
\fICHROOT_DIR\fR
directory\&. Only absolute paths are supported\&. No SELINUX support\&.
.RE
.PP
\fB\-P\fR, \fB\-\-prefix\fR\ \&\fIPREFIX_DIR\fR
.RS 4
Apply changes to configuration files under the root filesystem found under the directory
\fIPREFIX_DIR\fR\&. 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\&.
.RE
.PP
\fB\-s\fR, \fB\-\-sha\-rounds\fR\ \&\fIROUNDS\fR
.RS 4
legt die Anzahl von Runden beim Verschl\(:usseln von Passw\(:ortern fest\&.
.sp
You can only use this option with crypt method:
\fISHA256\fR \fISHA512\fR
.sp
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
/etc/login\&.defs\&.
.sp
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\&.
.RE
.SH "WARNUNGEN"
.PP
Achten Sie darauf, dass die Zugriffsrechte der unverschl\(:usselten Datei beziehungsweise
\fBUMASK\fR
ausschlie\(ssen, dass andere Benutzer sie lesen k\(:onnen\&.
.SH "KONFIGURATION"
.PP
The following configuration variables in
/etc/login\&.defs
change the behavior of this tool:
.PP
\fBENCRYPT_METHOD\fR (string)
.RS 4
This defines the system default encryption algorithm for encrypting passwords (if no algorithm is specified on the command line)\&.
.sp
It can take one of these values:
\fIDES\fR
(default),
\fIMD5\fR, \fISHA256\fR, \fISHA512\fR\&. MD5 and DES should not be used for new hashes, see
crypt(5)
for recommendations\&.
.sp
Note: this parameter overrides the
\fBMD5_CRYPT_ENAB\fR
variable\&.
.RE
.PP
\fBMD5_CRYPT_ENAB\fR (boolean)
.RS 4
Indicate if passwords must be encrypted using the MD5\-based algorithm\&. If set to
\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
\fIno\fR
if you need to copy encrypted passwords to other systems which don\*(Aqt understand the new algorithm\&. Default is
\fIno\fR\&.
.sp
This variable is superseded by the
\fBENCRYPT_METHOD\fR
variable or by any command line option used to configure the encryption algorithm\&.
.sp
This variable is deprecated\&. You should use
\fBENCRYPT_METHOD\fR\&.
.RE
.PP
\fBSHA_CRYPT_MIN_ROUNDS\fR (number), \fBSHA_CRYPT_MAX_ROUNDS\fR (number)
.RS 4
When
\fBENCRYPT_METHOD\fR
is set to
\fISHA256\fR
or
\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)\&.
.sp
With a lot of rounds, it is more difficult to brute force the password\&. But note also that more CPU resources will be needed to authenticate users\&.
.sp
If not specified, the libc will choose the default number of rounds (5000), which is orders of magnitude too low for modern hardware\&.
.sp
The values must be inside the 1000\-999,999,999 range\&.
.sp
If only one of the
\fBSHA_CRYPT_MIN_ROUNDS\fR
or
\fBSHA_CRYPT_MAX_ROUNDS\fR
values is set, then this value will be used\&.
.sp
If
\fBSHA_CRYPT_MIN_ROUNDS\fR
>
\fBSHA_CRYPT_MAX_ROUNDS\fR, the highest value will be used\&.
.RE
.SH "DATEIEN"
.PP
/etc/passwd
.RS 4
Informationen zu den Benutzerkonten
.RE
.PP
/etc/shadow
.RS 4
gesch\(:utzte Informationen zu den Benutzerkonten
.RE
.PP
/etc/login\&.defs
.RS 4
konfiguriert die Shadow\-Hilfsprogramme\&.
.RE
.SH "SIEHE AUCH"
.PP
\fBpasswd\fR(1),
\fBnewusers\fR(8),
\fBlogin.defs\fR(5),
\fBuseradd\fR(8)\&.