PWCONV(8)                 (02/07/2020)                  PWCONV(8)

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

     SYNOPSIS
          pwconv [options]

          pwunconv [options]

          grpconv [options]

          grpunconv [options]

     DESCRIPTION
          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 /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 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 /etc/shadow.

          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.

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     OPTIONS
          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.

     BUGS
          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 groups.

     CONFIGURATION
          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)

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              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.

     FILES
          /etc/login.defs
              Shadow password suite configuration.

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

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