Linux useradd userdel usermod passwd gpasswd

#create new user names tester 
sudo useradd tester

# add user to group 
sudo usermod -a -G group1,group2 username

# remove user from group sudo gpasswd -d username groupname

#delete user tester
sudo userdel  tester 

sudo userdel  -r tester  # delete files tester created. 

#completed delete user .forbidden
[root@localhost ~]# id tester 
  1000
[root@localhost ~]# find / -uid 1000
/home/tester
/home/tester/.log
/home/tester/.git
[root@localhost ~]# find / -user tester -exec rm -rf {} \;

#set password to user tester 
sodo passwd tester 

#show groups
 cat /etc/group

# create a group sudo groupadd groupname

#delete a group sudo groupdel groupname

#change a user's primary group sudo usermod -g groupname username sudo usermod -g developers tester

# append group to user
sudo usermod -aG groupname username # remove group from user 
 gpasswd -d username groupname 

#show users in group
sudo groups groupname