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PWCONV(8) 系统管理命令 PWCONV(8)


pwconv, pwunconv, grpconv, grpunconv - 在影子密码和组以及其它直接转换


pwconv [选项]

pwunconv [选项]

grpconv [选项]

grpunconv [选项]


The pwconv command creates shadow from passwd and an optionally existing shadow.

The pwunconv command creates passwd from passwd and shadow and then removes shadow.

The grpconv command creates gshadow from group and an optionally existing gshadow.

The grpunconv command creates group from group and gshadow and then removes gshadow.

These four programs all operate on the normal and shadow password and group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow.

Each program acquires the necessary locks before conversion. pwconv and grpconv are similar. First, entries in the shadowed file which don't exist in the main file are removed. Then, shadowed entries which don't have `x' as the password in the main file are updated. Any missing shadowed entries are added. Finally, passwords in the main file are replaced with `x'. These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand.

pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and PASS_WARN_AGE from /etc/login.defs when adding new entries to /etc/shadow.

Likewise pwunconv and grpunconv are similar. Passwords in the main file are updated from the shadowed file. Entries which exist in the main file but not in the shadowed file are left alone. Finally, the shadowed file is removed. Some password aging information is lost by pwunconv. It will convert what it can.


The options which apply to the pwconv, pwunconv, grpconv, and grpunconv commands are:

-h, --help


-R, --root CHROOT_DIR

Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.


Errors in the password or group files (such as invalid or duplicate entries) may cause these programs to loop forever or fail in other strange ways. Please run pwck and grpck to correct any such errors before converting to or from shadow passwords or groups.


The following configuration variable in /etc/login.defs changes the behavior of grpconv and grpunconv:


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。

The following configuration variables in /etc/login.defs change the behavior of pwconv:

PASS_MAX_DAYS (number)

一个密码可以使用的最大天数。如果密码比这旧,将会强迫更改密码。如果不指定,就假定为 -1,这会禁用这个限制。

PASS_MIN_DAYS (number)

两次更改密码时间的最小间隔。将会拒绝任何早于此的更改密码的尝试。如果不指定,假定为 -1,将会禁用这个限制。

PASS_WARN_AGE (number)

密码过期之前给出警告的天数。0 表示只有只在过期的当天警告,负值表示不警告。如果没有指定,不会给警告。



Shadow 密码套件配置。


grpck(8), login.defs(5), pwck(8).

2020-02-07 shadow-utils 4.8.1