Linux 5: User Management

Passwd

User details are stored in /etc/passwd file. Wikipedia link

dodan:x:1000:1000:Dodan,,,:/home/dodan:/bin/bash

It can be read as Username | Password | User ID | Group ID | Real Name and contact details | Home folder | Start-up program

Group

Locates at /etc/group

dodan:x:1001:dodan

It can be read as Group name | password (Generally password is not used, hence it is empty/blank. It can store encrypted password.) | Group ID | Users in this group

Real passwords

User passwords are really stored in /etc/shadow file encrypted in SHA.

dodan:$6$xKL4hV3x$PybQLVub4Kqe2jI2b7GG23iEYKVwujSRE0.3cP6V6u9vaOQTbxR8F0tvD.JAbTcBlpqnO2gCIZPwgIUShn1V20:16213:0:99999:7:::

It can be read as
Username | encrypted password | date of last password change | minimum password age | maximum password age

• Date of last password change. The date of the last password change, expressed as the number of days since Jan 1, 1970
• Minimum password age. The minimum password age is the number of days the user will have to wait before she will be allowed to change her password again.
• Maximum password age. The maximum password age is the number of days after which the user will have to change her password.

Wikipedia article