More information about the Linux/etc/shadow file

Unlike the linux/etc/passwd file, the Linux/etc/shadow file is a file that only the system administrator has the right to view and modify, and the system administrator should figure out the corresponding meaning of each character segment in the Linux/etc/shadow file. Clear management of the specific meaning.

The record line in the Linux/etc/shadow file corresponds to one by one in/etc/passwd, which is automatically generated by the PWCONV command based on the data in the/etc/passwd. Its file format is similar to/etc/passwd and consists of several fields, separated by ":" Between the fields. These fields are:
Login: Encrypted password: Last modified: Minimum time interval: Maximum time interval: Warning Time: Inactivity time: Expiry time: Flag
1) "Login name" is a user account that matches the login name in the/etc/passwd file
2) The password field holds the encrypted user password Word, which is 13 characters long. If null, the corresponding user does not have a password, the password is not required at logon, and if it contains characters that are not part of the collection {./0-9a-za-z}, the corresponding user cannot log on.
3) "Last Modified Time" represents the number of days from the time the user last modified the password. The beginning of time may not be the same for different systems. For example, in Scolinux, the starting point for this time is January 1, 1970.
4) "Minimum time interval" refers to the minimum number of days required between changing the password two times.
5) "Maximum time interval" refers to the maximum number of days that a password remains valid.
6) The "Warning Time" field represents the number of days from the beginning of the system warning user to the official expiration of the user's password.
7) "Inactivity Time" represents the maximum number of days that a user does not have a login activity but the account remains valid.
8) The "Expiration Time" field gives an absolute number of days, and if this field is used, the lifetime of the corresponding account is given. After expiry, the account is no longer a legitimate account, and can no longer be used to log on.

Here is an example of/etc/shadow:
#cat/etc/shadow
Root:dnakfw28zf38w:8764:0:168:7:::
daemon:*::0:0::::
bin:*::0:0::::
sys:*::0:0::::
adm:*::0:0::::
uucp:*::0:0::::
nuucp:*::0:0::::
auth:*::0:0::::
cron:*::0:0::::
listen:*::0:0::::
lp:*::0:0::::
Sam:ekdiseclwpdsa:9740:0:0::

More information about the Linux/etc/shadow file