]> Thomas Kłoczko kloczek@pld.org.pl Creation, 2006 Nicolas François nicolas.francois@centraliens.net shadow-utils maintainer, 2007 - now chgpasswd 8 System Management Commands shadow-utils &SHADOW_UTILS_VERSION; chgpasswd update group passwords in batch mode chgpasswd options 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 overwritten 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. The options which apply to the chgpasswd command are: -c, --crypt-method Use the specified method to encrypt the passwords. The available methods are BCRYPT, DES, MD5, SHA256, SHA512, YESCRYPT and NONE if your libc supports 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. Only absolute paths are supported. -s, --sha-rounds Use the specified number of rounds to encrypt the passwords. You can only use this option with crypt method: BCRYPT SHA256 SHA512 YESCRYPT By default, the number of rounds for BCRYPT is defined by the BCRYPT_MIN_ROUNDS and BCRYPT_MAX_ROUNDS variables in /etc/login.defs. A minimal value of 4 and a maximal value of 31 will be enforced for BCRYPT. The default number of rounds is 13. By default, the number of rounds for SHA256 or SHA512 is defined by the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in /etc/login.defs. A minimal value of 1000 and a maximal value of 999,999,999 will be enforced for SHA256 and SHA512. The default number of rounds is 5000. By default, the number of rounds for YESCRYPT is defined by the YESCRYPT_COST_FACTOR in /etc/login.defs. A minimal value of 1 and a maximal value of 11 will be enforced for YESCRYPT. The default number of rounds is 5. 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. The following configuration variables in /etc/login.defs change the behavior of this tool: &BCRYPT_MIN_ROUNDS; &ENCRYPT_METHOD; &MAX_MEMBERS_PER_GROUP; &MD5_CRYPT_ENAB; &SHA_CRYPT_MIN_ROUNDS; &YESCRYPT_COST_FACTOR; /etc/group Group account information. /etc/gshadow Secure group account information. /etc/login.defs Shadow password suite configuration. gpasswd1 , groupadd8 , login.defs5 .