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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | BUGS | CONFIGURATION | FILES | SEE ALSO | COLOPHON |
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PWCONV(8) System Management Commands PWCONV(8)
pwconv, pwunconv, grpconv, grpunconv - convert between the
system's shadowed and plain account files
pwconv [options]
pwunconv [options]
grpconv [options]
grpunconv [options]
The pwconv command creates shadow from passwd and an optionally
existing shadow.
The pwunconv command creates a plain passwd from shadowed passwd
and shadow and then removes shadow.
The grpconv command creates gshadow from group and an optionally
existing gshadow.
The grpunconv command creates plain group from shadowed group and
gshadow and then removes gshadow.
These four programs all operate on the normal and shadow password
and group files: /etc/passwd, /etc/group, /etc/shadow, and
/etc/gshadow.
Each program acquires the necessary locks before conversion.
pwconv and grpconv are similar. First, entries in the shadowed
file which don't exist in the plain file are removed. Then,
entries in the shadowed file which don't have `x' as the password
in plain file are updated. Any missing shadowed entries are added.
Finally, passwords in the plain file are replaced with `x'. These
programs can be used for initial conversion as well to update the
shadowed file if the plain file has been edited by hand.
pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and
PASS_WARN_AGE from /etc/login.defs when adding new entries to
/etc/shadow.
Likewise pwunconv and grpunconv are similar. Passwords in the
plain file are updated from the shadowed file. Entries which exist
in the plain file but not in the shadowed file are left alone.
Finally, the shadowed file is removed. Some password aging
information is lost by pwunconv. It will convert what it can.
The options which apply to the pwconv, pwunconv, grpconv, and
grpunconv commands are:
-h, --help
Display help message and exit.
-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.
Errors in the password or group files (such as invalid or
duplicate entries) may cause these programs to loop forever or
fail in other strange ways. Please run pwck and grpck to correct
any such errors before converting to or from shadowed files.
The following configuration variable in /etc/login.defs changes
the behavior of grpconv and grpunconv:
MAX_MEMBERS_PER_GROUP (number)
Maximum members per group entry. When the maximum is reached,
a new group entry (line) is started in /etc/group (with the
same name, same password, and same GID).
The default value is 0, meaning that there are no limits in
the number of members in a group.
This feature (split group) permits to limit the length of
lines in the group file. This is useful to make sure that
lines for NIS groups are not larger than 1024 characters.
If you need to enforce such limit, you can use 25.
Note: split groups may not be supported by all tools (even in
the Shadow toolsuite). You should not use this variable unless
you really need it.
The following configuration variables in /etc/login.defs change
the behavior of pwconv:
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
value of -1 means no warning is given. If not specified, no
warning will be provided.
/etc/login.defs
Shadow password suite configuration.
grpck(8), login.defs(5), pwck(8).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about
the project can be found at
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug report
for this manual page, send it to
pkg-shadow-devel@alioth-lists.debian.net. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-10.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
shadow-utils 4.18.0 08/11/2025 PWCONV(8)
Pages that refer to this page: gshadow(5), passwd(5), passwd(5@@shadow-utils), shadow(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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