CHPASSWD(8)

名称
chpasswd - 批量更新密码

大纲

chpasswd [options]

描述

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 passwords must be supplied in clear-text, and are 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 overwritten with the -e or -c options.

chpasswd first updates all the passwords in memory, and then commits all the changes to disk if no errors occurred for any user.

此命令一般用于需要一次创建很多用户的大型系统。

选项

The options which apply to the chpasswd command are:

-c, --crypt-method METHOD
    使用指定的方法加密密码。

    The available methods are SHA256, SHA512, and NONE if your libc supports these methods.

    By default (if none of the -c or -e options are specified), the encryption method is defined by the ENCRYPT_METHOD variable of /etc/login.defs.

-e, --encrypted
    提供的密码是已经加密了的

-h, --help
    显示帮助信息并退出。

-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. No SELINUX support.

-P, --prefix PREFIX_DIR
    Apply changes to configuration files under the root filesystem found under the directory PREFIX_DIR. This option does not chroot and is intended for preparing a cross-compilation target. Some limitations: NIS and LDAP users/groups are not verified. PAM authentication is using the host files. No SELINUX support.

-s, --sha-rounds ROUNDS
    使用指定次数的轮转来加密密码。

    You can only use this option with crypt method: SHA256 SHA512

    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.

CAVEATS

记住要设置权限或者掩码来阻止其它用户对未加密文件的读取。

配置文件

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 is specified on the command line).

    It can take one of these values: SHA256, SHA512 (default), . See crypt(5) for recommendations.

    History: This variable is used by other programs, which may still default to unsafe algorithms such as DES. To avoid using unsafe algorithms, the variable should always be specified.

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 force 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), which is orders of magnitude too low for modern hardware.

    值必须在 1000 - 999,999,999 之间。

    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.

文件

/etc/passwd
    用户账户信息。

/etc/shadow
    安全用户账户信息。

/etc/login.defs
    Shadow 密码套件配置。

参见

passwd(1), newusers(8), login.defs(5), useradd(8).