Linux: User and Group file interpretation (/etc/passwd,/etc/shadow,/etc/group,/etc/gshadow)

One, user files:/etc/passwd

[[email protected] ~]# Cat/etc/passwdroot:x:0:0:root:/root:/bin/bash 1 2 3 4 5 6 7 |  | | |     |      |   | |  | | |     |      |   |--the default shell used by the user |  | | |     |   |--User Home Directory |  | | |   |--User Finger Information (Note information) |   | | | |--user group ID (GID) |   | |--User ID (UID) | |--Password placeholder (password saved in/etc/shadow file) |--user name

Add user command: useradd [option] ... This file is the username operation.

The new user home directory defaults to/home/username, and the contents of the home directory are copied from the contents of the/etc/skel directory.

Second, the user password file:/etc/shadow

[[email protected] ~]# cat /etc/shadowroot:$1$. Tzs2yur$uq3.5xlbdehlkak9hkqzx/:16042:0:99999:7: blank: blank: Blank  1            2                             3   4    5   6  7    8   9 |            |                             |    |   |   |  |    |    |--reserved field, currently empty  |           |                             |   |    |   |  |    |--User Expiration Date (Units/day), This field specifies the number of days that the user has been invalidated (from January 1 to the date of 1970)  |           |                              |   |   |    |  |--disable this user for the number of days after the password expires  |            |                             |   |   |    |--how many days in advance warning user password will expire  |           |                              |   |   |--two times the maximum number of days to change the password interval  |            |                             |   | --Two days with minimum password change interval  |           |                              |--the last time the password was modified (Units/day), from January 01, 1970 to present days  |            |--user password (corresponding to the password placeholder in the/etc/passwd file), if the password is added "!!" Indicates that the user  |--user name is disabled (corresponding to the user name in the/etc/passwd file)   Note: Where the value of fields 4, 5, 6, 7, 8 is empty, the account can be used permanently

Set User password command: passwd [option] ... This file is the username operation.

Third, user group files:/etc/group

[Email protected] ~]# Cat/etc/grouproot:x:0:root |  | |   |--extra groups (can be multiple with "," separated) |   | |--group ID (GID) | |--Group Password placeholder |--group name

Add Group command: groupadd [option] ... GROUPNAME

Second, user group files:/etc/gshadow

[Email protected] ~]# cat/etc/gshadowroot: blank: blank: Root |    |    |    |--comma-delimited Group members |    |    |--a comma-delimited group Administrator | |--encrypted password |--group name

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Linux: User and Group file interpretation (/etc/passwd,/etc/shadow,/etc/group,/etc/gshadow)