]> chpasswd 8 System Management Commands chpasswd update passwords in batch mode chpasswd options The chpasswd command reads a list of user name and password pairs from standard input and uses this information to update a group of existing users. Each line is of the format: user_name:password By default the supplied password must be in clear-text, and is encrypted by chpasswd. Also the password age will be updated, if present. 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. chpasswd first update the password in memory, and then commit all the changes to disk if no errors occured for any users. The supplied passwords must be in clear-text. PAM is used to update the password in the system database according to the PAM chpasswd configuration. When chpasswd fails to update a password, it continues updating the passwords of the next users, and will return an error code on exit. 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 chpasswd command are: -c, --crypt-method Use the specified method to encrypt the passwords. The available methods are DES, MD5, and NONE. 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. -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. 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: &ENCRYPT_METHOD; &MD5_CRYPT_ENAB; &SHA_CRYPT_MIN_ROUNDS; /etc/passwd User account information. /etc/shadow Secure user account information. /etc/login.defs Shadow password suite configuration. /etc/pam.d/chpasswd PAM configuration for chpasswd. passwd1 , newusers8 , login.defs5 , useradd8 .