pwck(8) — Linux manual page


PWCK(8)                System Management Commands                PWCK(8)

NAME         top

       pwck - verify the integrity of password files

SYNOPSIS         top

       pwck [options] [PASSWORDFILE [ SHADOWFILE ]]

DESCRIPTION         top

       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:

       •   the correct number of fields

       •   a unique and valid user name

       •   a valid user and group identifier

       •   a valid primary group

       •   a valid home directory

       •   a valid login shell

       Checks for shadowed password information are enabled when the
       second file parameter SHADOWFILE is specified or when /etc/shadow
       exists on the system.

       These checks are the following:

       •   every passwd entry has a matching shadow entry, and every
           shadow entry has a matching passwd entry

       •   passwords are specified in the shadowed file

       •   shadow entries have the correct number of fields

       •   shadow entries are unique in shadow

       •   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. All other errors are
       warnings 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         top

       The -r and -s options cannot be combined.

       The options which apply to the pwck command are:

           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. Only
           absolute paths are supported.

       -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.


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

       NONEXISTENT (string)
           If a system account intentionally does not have a home
           directory that exists, this string can be provided in the
           /etc/passwd entry for the account to indicate this. The
           result is that pwck will not emit a spurious warning for this

       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, 0 will be assumed (which disables
           the restriction).

       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         top

           Group account information.

           User account information.

           Secure user account information.

EXIT VALUES         top

       The pwck command exits with the following values:


           invalid command syntax

           one or more bad password entries

           can't open password files

           can't lock password files

           can't update password files

           can't sort password files

SEE ALSO         top

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

COLOPHON         top

       This page is part of the shadow-utils (utilities for managing
       accounts and shadow password files) project.  Information about
       the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, send it to  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-15.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

shadow-utils 4.11.1            12/22/2023                        PWCK(8)

Pages that refer to this page: passwd(5@@shadow-utils)shadow(5)grpck(8)pwconv(8)