pwck

PWCK(8)                   System Management Commands                   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.
       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).

       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).

shadow-utils 4.8.1                11/29/2022                           PWCK(8)