pwck






pwck − verify integrity of password files

pwck [options] [passwd [ shadow ]]



     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









                             ‐2‐


should be used in those circumstances to remove the
offending entry.



     The −r and −s options cannot be combined.

     The options which apply to the pwck command are:

     −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.



     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.











                             ‐3‐




     /etc/group
     Group account information.

     /etc/passwd
     User account information.

     /etc/shadow
     Secure user account information.



     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



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