Working with user account on CentOS

1.Listing user password in Cent

cat /etc/password

2.Changing a specific account in Cent

passwd fptuser

3. Renaming an user name of an account

id fptuser 

Return: uid=500(fptuser) gid=502(fptuser) groups=502(fptuser),503(fpt)

A. Use the usermod command to change user name under Linux. it modifies the system account files to reflect the changes that are specified on the command line.

Syntax is as follows
usermod -l login-name old-name

Where,

=> The name of the user will be changed from old-name to login_name. Nothing else is changed. In particular, the user's home directory name should probably be changed to
reflect the new login name.

usermod -u UID username

Where,
=> The numerical value of the user's ID (UID) . This value must be unique, unless the -o option is used. The value must be non-negative. Values between 0 and 99 are typically reserved for system accounts. Any files which the user owns and which are located in the directory tree rooted at the user's home directory will have the file user ID changed automatically. Files outside of the user's home directory must be altered
manually.

Task: Change username from tom to jerry

Type usermod command as follows:
# id tom
# usermod -l jerry tom
# id jerry
# id tom

Task: Change user tom UID from 5001 to 10000

Type usermod command as follows
# id tom
# usermod -u 10000 tom
# id tom

Read man page of usermod for more information.