'\" t
.\"     Title: passwd
.\"    Author: Julianne Frances Haugh
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 2025-06-27
.\"    Manual: User Commands
.\"    Source: shadow-utils 4.18.0
.\"  Language: Chinese Simplified
.\"
.TH "PASSWD" "1" "2025-06-27" "shadow\-utils 4\&.18\&.0" "User Commands"
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.SH "名称"
passwd \- 更改用户密码
.SH "大纲"
.HP \w'\fBpasswd\fR\ 'u
\fBpasswd\fR [\fIoptions\fR] [\fILOGIN\fR]
.SH "描述"
.PP
The
\fBpasswd\fR
command changes passwords for user accounts\&. A regular user can only change the password for their own account, while the superuser can change the password for any account\&. The
\fBpasswd\fR
also changes the account or associated password validity period\&.
.SS "密码更改"
.PP
If the account has a non\-empty password, the user is first prompted to enter their current password\&. The entered password is encrypted and compared to the stored value\&. The user has only one attempt to enter the correct password\&. The superuser can bypass this step to allow changing forgotten passwords\&.
.PP
After the password has been entered, password aging information is checked to determine if the user is permitted to change the password at this time\&. If not,
\fBpasswd\fR
refuses to change the password and exits\&.
.PP
The user is then prompted twice for a replacement password\&. The second entry is compared against the first and both are required to match for the password to be changed\&.
.PP
Then, the password is tested for complexity\&.
\fBpasswd\fR
rejects passwords that do not meet the complexity requirements\&. Do not include the system default erase or kill characters\&.
.SS "关于用户密码的提示"
.PP
The security of a password depends on the strength of the encryption algorithm and the size of the key space\&. The legacy
\fIUNIX\fR
System encryption method is based on the NBS DES algorithm\&. More recent methods are now recommended (see
\fBENCRYPT_METHOD\fR)\&. The size of the key space depends on the randomness of the selected password\&.
.PP
Compromises in password security normally result from careless password selection or handling\&. For this reason, you should not select a password which appears in a dictionary or one that must be written down\&. The password should also not be a proper name, your license number, birth date, or street address\&. Any of these may be used as guesses to violate system security\&.
.PP
As a general guideline, passwords should be long and random\&. It\*(Aqs fine to use simple character sets, such as passwords consisting only of lowercase letters, if that helps memorizing longer passwords\&. For a password consisting only of lowercase English letters randomly chosen, and a length of 32, there are 26^32 (approximately 2^150) different possible combinations\&. Being an exponential equation, it\*(Aqs apparent that the exponent (the length) is more important than the base (the size of the character set)\&.
.PP
You can find advice on how to choose a strong password on https://en\&.wikipedia\&.org/wiki/Password_strength
.SH "选项"
.PP
The options which apply to the
\fBpasswd\fR
command are:
.PP
\fB\-a\fR, \fB\-\-all\fR
.RS 4
This option can be used only with
\fB\-S\fR
and causes show status for all users\&.
.RE
.PP
\fB\-d\fR, \fB\-\-delete\fR
.RS 4
Deletes a user\*(Aqs password, making it empty\&. This command sets the account to be passwordless\&.
.RE
.PP
\fB\-e\fR, \fB\-\-expire\fR
.RS 4
让一个账户的密码立即过期。这可以强制一个用户下次登录时更改密码。
.RE
.PP
\fB\-h\fR, \fB\-\-help\fR
.RS 4
显示帮助信息并退出。
.RE
.PP
\fB\-i\fR, \fB\-\-inactive\fR\ \&\fIINACTIVE\fR
.RS 4
This option is used to disable an account after the password has been expired for a number of days\&. After a user account has had an expired password for
\fIINACTIVE\fR
days, the user may no longer sign on to the account\&.
.RE
.PP
\fB\-k\fR, \fB\-\-keep\-tokens\fR
.RS 4
表示密码更改只应该因为认证口令(密码)过期更改。用户希望保持他们尚未过期的口令。
.RE
.PP
\fB\-l\fR, \fB\-\-lock\fR
.RS 4
锁定指定账户的密码。此选项通过将密码更改为一个不可能与加密值匹配的值来禁用(它在密码开头添加一个\(lq!\(rq)。
.sp
Note that this does not disable the account\&. The user may still be able to login using another authentication token (e\&.g\&. an SSH key)\&. To disable the account, administrators should use
\fBusermod \-\-expiredate 1\fR
(this sets the account\*(Aqs expire date to 1970\-01\-02)\&.
.sp
被锁定了密码的用户不允许更改密码。
.RE
.PP
\fB\-n\fR, \fB\-\-mindays\fR\ \&\fIMIN_DAYS\fR
.RS 4
Set the minimum number of days between password changes to
\fIMIN_DAYS\fR\&. A value of zero for this field indicates that the user may change their password at any time\&.
.RE
.PP
\fB\-q\fR, \fB\-\-quiet\fR
.RS 4
安静模式。
.RE
.PP
\fB\-r\fR, \fB\-\-repository\fR\ \&\fIREPOSITORY\fR
.RS 4
change password in
\fIREPOSITORY\fR
repository
.RE
.PP
\fB\-R\fR, \fB\-\-root\fR\ \&\fICHROOT_DIR\fR
.RS 4
Apply changes in the
\fICHROOT_DIR\fR
directory and use the configuration files from the
\fICHROOT_DIR\fR
directory\&. Only absolute paths are supported\&.
.RE
.PP
\fB\-P\fR, \fB\-\-prefix\fR\ \&\fIPREFIX_DIR\fR
.RS 4
Apply changes to configuration files under the root filesystem found under the directory
\fIPREFIX_DIR\fR\&. This option does not chroot and is intended for preparing a cross\-compilation target\&. Some limitations: NIS and LDAP users/groups are not verified\&. No PAM support\&. No SELINUX support\&.
.RE
.PP
\fB\-S\fR, \fB\-\-status\fR
.RS 4
显示账户状态信息。状态信息包含 7 个字段。首个字段是用户的登录名，第二个字段表示用户账户是否已经锁定密码(L)、没有密码 (NP)或者密码可用(P)，第三个字段给出最后一次更改密码的日期。接下来的四个字段分别是密码的最小年龄、最大年龄、警告期和禁用期。这些年龄以天为单位计算。
.RE
.PP
\fB\-u\fR, \fB\-\-unlock\fR
.RS 4
Unlock the password of the named account\&. This option re\-enables a password by changing the password back to its previous value (to the value before using the
\fB\-l\fR
option)\&.
.RE
.PP
\fB\-w\fR, \fB\-\-warndays\fR\ \&\fIWARN_DAYS\fR
.RS 4
Set the number of days of warning before a password change is required\&. The
\fIWARN_DAYS\fR
option is the number of days prior to password expiration during which the user is warned that their password is about to expire\&.
.RE
.PP
\fB\-x\fR, \fB\-\-maxdays\fR\ \&\fIMAX_DAYS\fR
.RS 4
Set the maximum number of days a password remains valid\&. After
\fIMAX_DAYS\fR, the password is required to be changed\&.
.sp
Passing the number
\fI\-1\fR
as
\fIMAX_DAYS\fR
will remove checking a password\*(Aqs validity\&.
.RE
.PP
\fB\-s\fR, \fB\-\-stdin\fR
.RS 4
This option is used to indicate that passwd should read the new password from standard input, which can be a pipe\&.
.RE
.SH "CAVEATS"
.PP
密码复杂性检查在每台机器间不同。用户应该选择适合的尽量复杂的密码。
.PP
在启动了 NIS 的系统上，如果没有登录 NIS 服务器，用户或许不能更改自己的密码。
.PP
\fBpasswd\fR
uses PAM to authenticate users and to change their passwords\&.
.SH "文件"
.PP
/etc/passwd
.RS 4
用户账户信息。
.RE
.PP
/etc/shadow
.RS 4
安全用户账户信息。
.RE
.PP
/etc/pam\&.d/passwd
.RS 4
PAM configuration for
\fBpasswd\fR\&.
.RE
.SH "退出值"
.PP
The
\fBpasswd\fR
command exits with the following values:
.PP
\fI0\fR
.RS 4
success
.RE
.PP
\fI1\fR
.RS 4
permission denied
.RE
.PP
\fI2\fR
.RS 4
invalid combination of options
.RE
.PP
\fI3\fR
.RS 4
unexpected failure, nothing done
.RE
.PP
\fI4\fR
.RS 4
unexpected failure,
passwd
file missing
.RE
.PP
\fI5\fR
.RS 4
passwd
file busy, try again
.RE
.PP
\fI6\fR
.RS 4
invalid argument to option
.RE
.PP
\fI10\fR
.RS 4
an error was returned by
pam(3)
.RE
.SH "参见"
.PP
\fBchpasswd\fR(8),
\fBmakepasswd\fR(1),
\fBpasswd\fR(5),
\fBshadow\fR(5),
\fBusermod\fR(8)\&.
.PP
The following web page comically (yet correctly) compares the strength of two different methods for choosing a password: "https://xkcd\&.com/936/"