shadow(5) File Formats and Configuration shadow(5) shadow - shadow is a file which contains the password information for the system's accounts and optional aging information. , . 9 , (<<:>>), : login name , . encrypted password This field may be empty, in which case no passwords are required to authenticate as the specified login name. However, some applications which read the /etc/shadow file may decide not to permit any access at all if the password field is empty. , , , . , . Refer to crypt(3) for details on how this string is interpreted. If the password field contains some string that is not a valid result of crypt(3), for instance ! or *, the user will not be able to use a unix password to log in (but the user may log in the system by other means). date of last password change , 1 1970 00:00 UTC. 0 -- . , . minimum password age , . 0 , . maximum password age , . . . , , (. ). , . password warning period (. ), . 0 , . password inactivity period (. ), ( ). . . , . account expiration date , 1 1970 00:00 UTC. , ' . , . , , . , . 0, , , , 1 1970 . reserved field . /etc/passwd . /etc/shadow . /etc/shadow- /etc/shadow. , shadow, . . chage(1), login(1), passwd(1), passwd(5), pwck(8), pwconv(8), pwunconv(8), su(1), sulogin(8). shadow-utils 4.16.0 02/07/2024 shadow(5)