PWCK(8) System Management Commands PWCK(8)
NAME
pwck - verify the integrity of password files
SYNOPSIS
pwck [options] [PASSWORDFILE [ SHADOWFILE ]]
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
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
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. 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.
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).
shadow-utils 4.13 03/23/2023 PWCK(8)
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