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:

       •   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

       shadow checks are enabled when a second file parameter 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 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:

       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 account.

       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

       /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).