pwconv(8) — Linux manual page


PWCONV(8)              System Management Commands              PWCONV(8)

NAME         top

       pwconv, pwunconv, grpconv, grpunconv - convert to and from shadow
       passwords and groups

SYNOPSIS         top

       pwconv [options]

       pwunconv [options]

       grpconv [options]

       grpunconv [options]

DESCRIPTION         top

       The pwconv command creates shadow from passwd and an optionally
       existing shadow.

       The pwunconv command creates passwd from passwd and shadow and
       then removes shadow.

       The grpconv command creates gshadow from group and an optionally
       existing gshadow.

       The grpunconv command creates group from 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

       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 main file are removed. Then,
       shadowed entries which don't have `x' as the password in the main
       file are updated. Any missing shadowed entries are added.
       Finally, passwords in the main file are replaced with `x'. These
       programs can be used for initial conversion as well to update the
       shadowed file if the main file is 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

       Likewise pwunconv and grpunconv are similar. Passwords in the
       main file are updated from the shadowed file. Entries which exist
       in the main 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.

OPTIONS         top

       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.

BUGS         top

       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 shadow passwords or


       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.

FILES         top

           Shadow password suite configuration.

SEE ALSO         top

       grpck(8), login.defs(5), pwck(8).

COLOPHON         top

       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 
       ⟨⟩.  If you have a bug
       report for this manual page, send it to  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2024-06-15.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  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
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       (which is not part of the original manual page), send a mail to

shadow-utils 4.14.0            06/15/2024                      PWCONV(8)

Pages that refer to this page: gshadow(5)passwd(5)passwd(5@@shadow-utils)shadow(5)