PWCK(8)                   (02/07/2020)                    PWCK(8)

     NAME
          pwck - verify integrity of password files

     SYNOPSIS
          pwck [options] [passwd [ shadow ]]

     DESCRIPTION
          The pwck command verifies the integrity of the users and
          authentication information. It checks that all entries in
          /etc/passwd and /etc/shadow have the proper format and
          contain valid data. The user is prompted to delete entries
          that are improperly formatted or which have other
          uncorrectable errors.

          Checks are made to verify that each entry has:

          +o   the correct number of fields

          +o   a unique and valid user name

          +o   a valid user and group identifier

          +o   a valid primary group

          +o   a valid home directory

          +o   a valid login shell

          shadow checks are enabled when a second file parameter is
          specified or when /etc/shadow exists on the system.

          These checks are the following:

          +o   every passwd entry has a matching shadow entry, and
              every shadow entry has a matching passwd entry

          +o   passwords are specified in the shadowed file

          +o   shadow entries have the correct number of fields

          +o   shadow entries are unique in shadow

          +o   the last password changes are not in the future

          The checks for correct number of fields and unique user name
          are fatal. If the entry has the wrong number of fields, the
          user will be prompted to delete the entire line. If the user
          does not answer affirmatively, all further checks are
          bypassed. An entry with a duplicated user name is prompted
          for deletion, but the remaining checks will still be made.

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     PWCK(8)                   (02/07/2020)                    PWCK(8)

          All other errors are warning and the user is encouraged to
          run the usermod command to correct the error.

          The commands which operate on the /etc/passwd file are not
          able to alter corrupted or duplicated entries.  pwck should
          be used in those circumstances to remove the offending
          entry.

     OPTIONS
          The -r and -s options cannot be combined.

          The options which apply to the pwck command are:

          --badname
              Allow names that do not conform to standards.

          -h, --help
              Display help message and exit.

          -q, --quiet
              Report errors only. The warnings which do not require
              any action from the user won't be displayed.

          -r, --read-only
              Execute the pwck command in read-only mode.

          -R, --root CHROOT_DIR
              Apply changes in the CHROOT_DIR directory and use the
              configuration files from the CHROOT_DIR directory.

          -s, --sort
              Sort entries in /etc/passwd and /etc/shadow by UID.

          By default, pwck operates on the files /etc/passwd and
          /etc/shadow. The user may select alternate files with the
          passwd and shadow parameters.

     CONFIGURATION
          The following configuration variables in /etc/login.defs
          change the behavior of this tool:

          PASS_MAX_DAYS (number)
              The maximum number of days a password may be used. If
              the password is older than this, a password change will
              be forced. If not specified, -1 will be assumed (which
              disables the restriction).

          PASS_MIN_DAYS (number)
              The minimum number of days allowed between password
              changes. Any password changes attempted sooner than this
              will be rejected. If not specified, -1 will be assumed
              (which disables the restriction).

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          PASS_WARN_AGE (number)
              The number of days warning given before a password
              expires. A zero means warning is given only upon the day
              of expiration, a negative value means no warning is
              given. If not specified, no warning will be provided.

     FILES
          /etc/group
              Group account information.

          /etc/passwd
              User account information.

          /etc/shadow
              Secure user account information.

     EXIT VALUES
          The pwck command exits with the following values:

          0
              success

          1
              invalid command syntax

          2
              one or more bad password entries

          3
              can't open password files

          4
              can't lock password files

          5
              can't update password files

          6
              can't sort password files

     SEE ALSO
          group(5), grpck(8), passwd(5), shadow(5), usermod(8).

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