pwunconv, grpconv, grpunconv − convert to and from
shadow passwords and groups
pwconv command creates shadow from
passwd and an optionally existing shadow.
pwunconv command creates passwd from
passwd and shadow and then removes
grpconv command creates gshadow from
group and an optionally existing gshadow.
grpunconv command creates group from
group and gshadow and then removes
programs all operate on the normal and shadow password and
group files: /etc/passwd, /etc/group, /etc/shadow, and
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.
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.
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.
which apply to the pwconv, pwunconv,
grpconv, and grpunconv commands are:
Display help message and
Apply changes in the
CHROOT_DIR directory and use the configuration files
from the CHROOT_DIR directory.
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 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).
value is 0, meaning that there are no limits in the number
of members in a group.
(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.
groups may not be supported by all tools (even in the Shadow
toolsuite). You should not use this variable unless you
really need it.
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
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