In this blog we are going to see the see Let's jump into the List of Commands. The user name is efxx Top 6 command-line based browsers read more...

• How to Add, Remove and Modify Users in Linux
• Create and modify a Group in Linux
• Check list of user Groups in Linux

In this blog we will learn how to create a new user new group and add them or remove them from the system or specified group. Basically this is the list of commands to do some useful things on Linux. Please usethem carefully and let me know the errors or any thing you need apart from this. Thank you. Add a user (the users password will be added in /etc/shadow with other user passwords)
Note: Basic difference "adduser, useradd". "adduser" will create home directory and add skeleton(directory where you can place the default files and all the folders) files to that directory where "useradd" wont create any home directory and files !
List of users in Linux

$ cut -d: -f1 /etc/passwd
or
$ awk -F: '{ print $1,"   \t" $NF,"   \t",$(NF -1)}' /etc/passwd|sed 's#$#\n------------------------------------------------------------------------#g'

List of users has Root access

$ awk -F: '{ print $1,"   \t" $NF,"   \t",$(NF -1)}' /etc/passwd|grep "/bin/bash"

List of user don't have login access

$ awk -F: '{ print $1,"   \t" $NF,"   \t",$(NF -1)}' /etc/passwd|grep "nologin"

$ sudo adduser newusername
or
$ sudo useradd -m newusername

Add user without password

$ sudo adduser --disabled-password --gecos "" USERNAME

Remove password from existing user account and disable it untill add new password from sudo user

$ passwd -d linuxtechi

Rename user

$ sudo usermod -l new-user-name old-user-name

View users UID using command

$ id -u newusername 

PID for all the groups for efx

$ id efx

To change UID of user efxx

$ usermod -u [New-user-id] [username]

View all PID (process id) for programs

$ ps -u efxx

Add user in sudo user

$ sudo usermod -aG sudo username

Kill the process other user process

$ pkill -u username 1532

Kill all the process owned by the user

$ pkill -9 -u username

Delete a User in Linux

$ sudo deluser username
or
$ sudo userdel username

Delete user with files

$ sudo userdel -r username

Change user password

$ passwd username

Create a new group (view the group file /etc/groups)

$ sudo addgroup groupname
or
$ sudo groupadd groupname

Assign a password to group

$ sudo gpasswd groupname

View all the group list

$ getent group

Delete the group with group name

$ sudo delgroup groupname
or
$ sudo groupdel groupname

To check a user group

$ groups efxx

Check owner groups

$ groups

Add a User to a Group in Linux(postgress service to sudo group)

$ usermod -aG postgres efxx

Remove a User from a Group in Linux

$ gpasswd -d efxx postgres

Remove user form specific group

$ sudo deluser efxx postgres

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