Linux Users

New User
Check User
Set Password For Self
Set Password Different User
Create System Account
Delete User
/etc/passwd File
Related
Links

New User

Add new user.
Depending on the distribution it may or may not create a home directory.
The configuration can be seen under /etc/default/useradd.
The new account will have a UID above 1000

sudo useradd xxx

Add new user & explicitly create a home directory.

sudo useradd -m xxx

Check User

If the user was created successfully it will have an entry in the /etc/passwd file

cat /etc/passwd | grep -i 'xxx'

Set Password For Self

sudo passwd xxx

Set Password Different User

sudo passwd

Create System Account

Create a System Account
The new account will have a UID below 1000
Most distributions will not display this user on the logon screen

sudo useradd -r sysuser

Delete User

Delete user leaving the home directory behind.

sudo userdel xxx

Delete user and its related resources

sudo userdel -r xxx

/etc/passwd

Lists all the users on the system. Also

user:x:1000:1000:user:/home/u:/bin/bash

Column: UserName
Column: Password( Historically ) Modern systems have a hashed password located at /etc/shadow
Column: UID
Column: GID
Column: Gecos / User Information / Name ( Optional Field)
Column: Home directory
Column: Shell

/etc/shadow

user:$6$8dkZRIbbknoLsEgGjhgjyg786876V4w6UFwph:18390:0:99999:7:::

Column: Username
Column: Password Hash
Column: Days since Unix Epoch since password was last changed
Column: Days until the password can be changed again.
Column: Days until a password change is required since Unix Epoch
Column: Days before password expires that the user will be reminded to change password.
Column: Days until user password will be locked
Column: Days until account will be disabled