PASSWD(1) 用户命令 PASSWD(1)

passwd - 更改用户密码

passwd [选项] [登录]

The passwd command changes passwords for user accounts. A normal user may only change the password for their own account, while the superuser may change the password for any account. passwd also changes the account or associated password validity period.


After the password has been entered, password aging information is checked to see if the user is permitted to change the password at this time. If not, passwd refuses to change the password and exits.


然后,测试密码的负责程度。一般来讲,密码应该包含 6 到 8 位字符,从下边的一个或多个集合中选择:

•数字 0 到 9

Care must be taken not to include the system default erase or kill characters. passwd will reject any password which is not suitably complex.

The security of a password depends upon the strength of the encryption algorithm and the size of the key space. The legacy UNIX System encryption method is based on the NBS DES algorithm. More recent methods are now recommended (see ENCRYPT_METHOD). The size of the key space depends upon the randomness of the password which is selected.


You can find advice on how to choose a strong password on

The options which apply to the passwd command are:

-a, --all

This option can be used only with -S and causes show status for all users.

-d, --delete


-e, --expire


-h, --help


-i, --inactive INACTIVE

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 INACTIVE days, the user may no longer sign on to the account.

-k, --keep-tokens


-l, --lock


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 usermod --expiredate 1 (this set the account's expire date to Jan 2, 1970).


-n, --mindays MIN_DAYS

Set the minimum number of days between password changes to MIN_DAYS. A value of zero for this field indicates that the user may change their password at any time.

-q, --quiet


-r, --repository REPOSITORY

change password in REPOSITORY repository

-R, --root CHROOT_DIR

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

-S, --status

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。

-u, --unlock

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 -l option).

-w, --warndays WARN_DAYS

Set the number of days of warning before a password change is required. The WARN_DAYS option is the number of days prior to the password expiring that a user will be warned that their password is about to expire.

-x, --maxdays MAX_DAYS

Set the maximum number of days a password remains valid. After MAX_DAYS, the password is required to be changed.

Passing the number -1 as MAX_DAYS will remove checking a password's validity.


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。

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



It can take one of these values: DES (default), MD5, SHA256, SHA512.

Note: this parameter overrides the MD5_CRYPT_ENAB variable.

MD5_CRYPT_ENAB (boolean)

Indicate if passwords must be encrypted using the MD5-based algorithm. If set to yes, new passwords will be encrypted using the MD5-based algorithm compatible with the one used by recent releases of FreeBSD. It supports passwords of unlimited length and longer salt strings. Set to no if you need to copy encrypted passwords to other systems which don't understand the new algorithm. Default is no.

This variable is superseded by the ENCRYPT_METHOD variable or by any command line option used to configure the encryption algorithm.

This variable is deprecated. You should use ENCRYPT_METHOD.




如果是 root,警告弱密码,但是仍然允许使用。



PASS_MAX_LEN (number), PASS_MIN_LEN (number)

Number of significant characters in the password for crypt(). PASS_MAX_LEN is 8 by default. Don't change unless your crypt() is better. This is ignored if MD5_CRYPT_ENAB set to yes.


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).

使用很多轮转,会让暴力破解更加困难。但是需要注意,认证用户时也会需要更多的 CPU 资源。

如果没有指定,libc 会选择默认的轮转数(5000)。

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.





Shadow 密码套件配置。

The passwd command exits with the following values:




permission denied


invalid combination of options


unexpected failure, nothing done


unexpected failure, passwd file missing


passwd file busy, try again


invalid argument to option

chpasswd(8), passwd(5), shadow(5), login.defs(5), usermod(8).
2020-01-23 shadow-utils 4.8.1