# phpman > man > pwconv(8)

[PWCONV(8)](https://www.chedong.com/phpMan.php/man/PWCONV/8/markdown)                            System Management Commands                            [PWCONV(8)](https://www.chedong.com/phpMan.php/man/PWCONV/8/markdown)



## 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.

## OPTIONS
       The options which apply to the **pwconv**, **pwunconv**, **grpconv**, and **grpunconv** commands are:

### -h --help
           Display help message and exit.

### -R --root
           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)
           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)](https://www.chedong.com/phpMan.php/man/grpck/8/markdown), [**login.defs**(5)](https://www.chedong.com/phpMan.php/man/login.defs/5/markdown), [**pwck**(8)](https://www.chedong.com/phpMan.php/man/pwck/8/markdown).



shadow-utils 4.8.1                           02/06/2024                                    [PWCONV(8)](https://www.chedong.com/phpMan.php/man/PWCONV/8/markdown)