pwck - verify integrity of password files
[options] [ passwd [ shadow ]]
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
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
•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
•shadow entries have the correct number
•shadow entries are unique in
•the last password changes are not in
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 cannot be combined.
The options which apply to the pwck
Display help message and exit.
Report errors only. The warnings which do not
require any action from the user won't be displayed.
Execute the pwck command in read-only
, --root CHROOT_DIR
Apply changes in the CHROOT_DIR
directory and use the configuration files from the CHROOT_DIR
Sort entries in /etc/passwd and /etc/shadow by
By default, pwck
operates on the files /etc/passwd and /etc/shadow. The
user may select alternate files with the passwd
The following configuration variables in /etc/login.defs change the behavior of
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).
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
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.
Group account information.
User account information.
Secure user account information.
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