chgpasswd
update group passwords in batch mode
see also :
gpasswd - groupadd
Synopsis
add an example, a script, a trick and tips
examples
source
etc/pam.d/{chpasswd,newusers,groupadd,groupdel,groupmod}
etc/pam.d/{chfn,chgpasswd,groupmems,chsh}
etc/default/useradd)
adduser chgpasswd chpasswd defaults.pam login login.defs
newusers
passwd shadow.cron.daily useradd.defaults LICENSE
description
The
chgpasswd command reads a list of group name and
password pairs from standard input and uses this information
to update a set of existing groups. Each line is of the
format:
group_name:password
By default the
supplied password must be in clear-text, and is
encrypted by chgpasswd.
The default
encryption algorithm can be defined for the system with the
ENCRYPT_METHOD variable of /etc/login.defs, and can
be overwiten with the -e, -m, or
-c options.
This command is
intended to be used in a large system environment where many
accounts are created at a single time.
options
The options
which apply to the chgpasswd command are:
-c,
--crypt-method
Use the specified method to
encrypt the passwords.
The available
methods are DES, MD5, NONE, and SHA256 or SHA512 if your
libc support these methods.
-e,
--encrypted
Supplied passwords are in
encrypted form.
-h,
--help
Display help message and
exit.
-m,
--md5
Use MD5 encryption instead of
DES when the supplied passwords are not encrypted.
-R,
--root CHROOT_DIR
Apply changes in the
CHROOT_DIR directory and use the configuration files
from the CHROOT_DIR directory.
-s,
--sha-rounds
Use the specified number of
rounds to encrypt the passwords.
The value 0
means that the system will choose the default number of
rounds for the crypt method (5000).
A minimal value
of 1000 and a maximal value of 999,999,999 will be
enforced.
You can only
use this option with the SHA256 or SHA512 crypt method.
By default, the
number of rounds is defined by the SHA_CRYPT_MIN_ROUNDS and
SHA_CRYPT_MAX_ROUNDS variables in /etc/login.defs.
caveats
Remember to set permissions or umask to prevent readability of
unencrypted files by other users.
You should make sure the passwords and the encryption method
respect the system's password policy.
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 superseded 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 1000-999,999,999 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.
files
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/login.defs
Shadow password suite configuration.
see also
gpasswd ,
groupadd , login.defs.