Provided by:
passwd_4.1.4.2+svn3283-3ubuntu5_i386 
CONFIGURATION
The following configuration variables in /etc/login.defs change the
behavior of this tool:
ENCRYPT_METHOD (string)
This defines the system default encryption algorithm for encrypting
passwords (if no algorithm are specified on the command line).
It can take one of these values: DES (default), MD5, SHA256,
SHA512.
Note: this parameter overrides the MD5_CRYPT_ENAB variable.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the PAM
configuration. It is recommended to set this variable consistently
with the PAM configuration.
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.
MD5_CRYPT_ENAB (boolean)
Indicate if passwords must be encrypted using the MD5-based
algorithm. If set to yes, new passwords will be encrypted using the
MD5-based algorithm compatible with the one used by recent releases
of FreeBSD. It supports passwords of unlimited length and longer
salt strings. Set to no if you need to copy encrypted passwords to
other systems which don't understand the new algorithm. Default is
no.
This variable is superceded by the ENCRYPT_METHOD variable or by
any command line option used to configure the encryption algorithm.
This variable is deprecated. You should use ENCRYPT_METHOD.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the PAM
configuration. It is recommended to set this variable consistently
with the PAM configuration.
SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the
number of SHA rounds used by the encryption algorithm by default
(when the number of rounds is not specified on the command line).
With a lot of rounds, it is more difficult to brute forcing the
password. But note also that more CPU resources will be needed to
authenticate users.
If not specified, the libc will choose the default number of rounds
(5000).
The values must be inside the 1000-999999999 range.
If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
values is set, then this value will be used.
If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value
will be used.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the PAM
configuration. It is recommended to set this variable consistently
with the PAM configuration.
/etc/group
/etc/gshadow
newgrp(1), groupadd(8), groupdel(8), groupmod(8), grpck(8), group(5),
gshadow(5).
04/09/2012 gpasswd(1)