Provided by: passwd_18.104.22.168-1ubuntu2_i386
pwconv, pwunconv, grpconv, grpunconv - convert to and from shadow
passwords and groups
The pwconv command creates shadow from passwd and an optionally
The pwunconv command creates passwd from passwd and shadow and then
The grpconv command creates gshadow from group and an optionally
The grpunconv command creates group from group and gshadow and then
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 dont
exist in the main file are removed. Then, shadowed entries which dont
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.
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.
The following configuration variable in /etc/login.defs changes the
behavior of grpconv and grpunconv:
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:
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).
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).
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
Shadow password suite configuration.
grpck(8), login.defs(5), pwck(8).