CHGPASSWD(8)

名称
chgpasswd - 批量更新组密码

大纲

chgpasswd [options]

描述

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 or -c options.

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 chgpasswd command are:

-c, --crypt-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.

-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.

-s, --sha-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。

您需要确保你吗和加密方法符合系统的密码策略。

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.

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).

    默认值是 0，意味着组中的成员数没有限制。

    此功能(分割组)允许限制组文件中的行长度。这对于确保 NIS 组的行比长于 1024 字符。

    如果要强制这个限制，可以使用 25。

    注意：分割组可能不受所有工具的支持(甚至在 Shadow 工具集中)。您不应该使用这个变量，除非真的需要。

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/group
    组账户信息。

/etc/gshadow
    安全组账户信息。

/etc/login.defs
    Shadow 密码套件配置。

参见

gpasswd(1), groupadd(8), login.defs(5).