{"id":292,"date":"2019-10-21T19:34:36","date_gmt":"2019-10-21T17:34:36","guid":{"rendered":"http:\/\/linuxboxen2.dk\/?p=292"},"modified":"2019-10-21T19:34:36","modified_gmt":"2019-10-21T17:34:36","slug":"chpasswd","status":"publish","type":"post","link":"https:\/\/www.linuxboxen.dk\/?p=292","title":{"rendered":"CHPASSWD"},"content":{"rendered":"
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CHPASSWD(8)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System Management Commands\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 CHPASSWD(8)<\/p>\n

NAME<\/p>\n

chpasswd – update passwords in batch mode<\/p>\n

SYNOPSIS<\/p>\n

chpasswd [options]<\/p>\n

DESCRIPTION<\/p>\n

The chpasswd command reads a list of user name and password pairs
\nfrom standard input and uses this information to update a group of
\nexisting users. Each line is of the format:<\/p>\n

user_name:password<\/p>\n

By default the passwords must be supplied in clear-text, and are
\nencrypted by chpasswd. Also the password age will be updated, if
\npresent.<\/p>\n

The default encryption algorithm can be defined for the system with
\nthe ENCRYPT_METHOD or MD5_CRYPT_ENAB variables of \/etc\/login.defs,
\nand can be overwitten with the -e, -m, or -c options.<\/p>\n

chpasswd first updates all the passwords in memory, and then commits
\nall the changes to disk if no errors occured for any user.<\/p>\n

This command is intended to be used in a large system environment
\nwhere many accounts are created at a single time.<\/p>\n

OPTIONS<\/p>\n

The options which apply to the chpasswd command are:<\/p>\n

-c, –crypt-method METHOD
\nUse the specified method to encrypt the passwords.<\/p>\n

The available methods are DES, MD5, NONE, and SHA256 or SHA512 if
\nyour libc support these methods.<\/p>\n

By default (if none of the -c, -m, or -e options are specified),
\nthe encryption method is defined by the ENCRYPT_METHOD or
\nMD5_CRYPT_ENAB variables of \/etc\/login.defs.<\/p>\n

-e, –encrypted
\nSupplied passwords are in encrypted form.<\/p>\n

-h, –help
\nDisplay help message and exit.<\/p>\n

-m, –md5
\nUse MD5 encryption instead of DES when the supplied passwords are
\nnot encrypted.<\/p>\n

-R, –root CHROOT_DIR
\nApply changes in the CHROOT_DIR directory and use the
\nconfiguration files from the CHROOT_DIR directory.<\/p>\n

-s, –sha-rounds ROUNDS
\nUse the specified number of rounds to encrypt the passwords.<\/p>\n

The value 0 means that the system will choose the default number
\nof rounds for the crypt method (5000).<\/p>\n

A minimal value of 1000 and a maximal value of 999,999,999 will
\nbe enforced.<\/p>\n

You can only use this option with the SHA256 or SHA512 crypt
\nmethod.<\/p>\n

By default, the number of rounds is defined by the
\nSHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
\n\/etc\/login.defs.<\/p>\n

CAVEATS<\/p>\n

Remember to set permissions or umask to prevent readability of
\nunencrypted files by other users.<\/p>\n

CONFIGURATION<\/p>\n

The following configuration variables in \/etc\/login.defs change the
\nbehavior of this tool:<\/p>\n

ENCRYPT_METHOD (string)
\nThis defines the system default encryption algorithm for
\nencrypting passwords (if no algorithm are specified on the
\ncommand line).<\/p>\n

It can take one of these values: DES (default), MD5, SHA256,
\nSHA512.<\/p>\n

Note: this parameter overrides the MD5_CRYPT_ENAB variable.<\/p>\n

MD5_CRYPT_ENAB (boolean)
\nIndicate if passwords must be encrypted using the MD5-based
\nalgorithm. If set to yes, new passwords will be encrypted using
\nthe MD5-based algorithm compatible with the one used by recent
\nreleases of FreeBSD. It supports passwords of unlimited length
\nand longer salt strings. Set to no if you need to copy encrypted
\npasswords to other systems which don’t understand the new
\nalgorithm. Default is no.<\/p>\n

This variable is superseded by the ENCRYPT_METHOD variable or by
\nany command line option used to configure the encryption
\nalgorithm.<\/p>\n

This variable is deprecated. You should use ENCRYPT_METHOD.<\/p>\n

SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
\nWhen ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the
\nnumber of SHA rounds used by the encryption algorithm by default
\n(when the number of rounds is not specified on the command line).<\/p>\n

With a lot of rounds, it is more difficult to brute forcing the
\npassword. But note also that more CPU resources will be needed to
\nauthenticate users.<\/p>\n

If not specified, the libc will choose the default number of
\nrounds (5000).<\/p>\n

The values must be inside the 1000-999,999,999 range.<\/p>\n

If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
\nvalues is set, then this value will be used.<\/p>\n

If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value
\nwill be used.<\/p>\n

FILES<\/p>\n

\/etc\/passwd
\nUser account information.<\/p>\n

\/etc\/shadow
\nSecure user account information.<\/p>\n

\/etc\/login.defs
\nShadow password suite configuration.<\/p>\n

SEE ALSO<\/p>\n

passwd(1), newusers(8), login.defs(5),useradd(8).<\/p>\n

COLOPHON<\/p>\n

This page is part of the shadow-utils (utilities for managing
\naccounts and shadow password files) project.\u00a0 Information about the
\nproject can be found at \u27e8http:\/\/pkg-shadow.alioth.debian.org\/\u27e9.\u00a0 If
\nyou have a bug report for this manual page, see
\n\u27e8http:\/\/pkg-shadow.alioth.debian.org\/getinvolved.php\u27e9.\u00a0 This page was
\nobtained from the project’s upstream Subversion repository
\n(svn:\/\/anonscm.debian.org\/pkg-shadow\/) on 2014-12-30.\u00a0 If you dis\u2010
\ncover any rendering problems in this HTML version of the page, or you
\nbelieve there is a better or more up-to-date source for the page, or
\nyou have corrections or improvements to the information in this
\nCOLOPHON (which is not part of the original manual page), send a mail
\nto\u00a0man-pages@man7.org<\/p>\n

shadow-utils 4.1.5.1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 01\/27\/2014\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 CHPASSWD(8)<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

<\/div>\n","protected":false},"excerpt":{"rendered":"

CHPASSWD(8)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System Management Commands\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 CHPASSWD(8) NAME chpasswd – update passwords in batch mode SYNOPSIS chpasswd [options] DESCRIPTION The chpasswd 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: user_name:password By default the passwords must […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":""},"categories":[8],"tags":[],"class_list":["post-292","post","type-post","status-publish","format-standard","hentry","category-shell"],"_links":{"self":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts\/292","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=292"}],"version-history":[{"count":0,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts\/292\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=292"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=292"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=292"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}