passwdThe passwd file is used for store Linux User account information. And it'll be located in /etc/passwd. It contains root and system user accounts information also. So if any wrong changes happened it affect full Linux system. It only have read permission for all user and have edit permission for root.
Location : /etc/passwd
1 - UserName : It is name of user which we created or superuser or system user. Here the first "kumar" is user name. Linux allows user name will be 1 to 32 characters.
2 - x : It is location of password file. Here x point out /etc/shadow.
3 - UserID (UID) : It is a unique number for user. It'll be create at the time of user creation. 0 for super user (root). 1 - 500 for system users. 501 to 60000 for normal users and 60001 to 65535 for duplicate user.
4 - GroupID (GID) : It is a unique number for group. It'll be create at the time of user creation. 0 for super user (root). 1 - 500 for system users. 501 to 60000 for normal users and 60001 to 65535 for duplicate user.
5 - User Info : It is normally full name of the user. While create user we can give full name of user. It is generally a short description of the login user. It will be show at login page. ( Ex. #useradd -c FullName username ).
6 - Home Directory : It is the path of the user directory. Normally files will be saved her when user create a file.
7 - Shell : It is the path of shell for the user. This shell will be used for the specific user.
* Use man pages for more help.