Linux Command Example – useradd, userdel, usermod, groupadd, last and lastb

In this tutorial I am going to explain some basic Linux command ” useradd, userdel, usermod, groupadd, last and lastb” that help to Linux beginner users as well as advanced users.

1. useradd

useradd command used to create a new user or updates default new user information. Below are the some example:

Add new user called sagar with default settings

# useradd sagar

Create new user with home directory in /opt

# useradd sagar -d /opt/sagar

Disable user account, In below example account will be disable from 28/4/2017.

# useradd sagar-e 2017-04-28

Set Warning to change password after after password expired, system will allow the user to login for 7 days with warning.

# useradd sagar -f 7

Set user (sagar) group as admin

# useradd sagar -g admin

Create user with the given encrypted password. Without password account will disabled.

# useradd sagar -p $1$d7

Change user shell C as the default login shell for the sagar.

# useradd sagar -s /bin/csh

2. userdel

userdel command to delete a user account and user’s related files.

Delete the user account

# userdel sagar

Delete the user account together with their home directory and all files inside it.

# userdel -r sagar

Delete the user with home directory as well file, forcefully even user is still login,

# userdel -f sagar

3. usermod

usermod command is used to modify the user account.

Create new home directory for sagar in /var/sagar and move old home directory contents to this directory.

# usermod -d /var/sagar sagar

Disable user account, In below example account will be disable from 20/8/2018.

# usermod -e 2018-08-28

Set warning to change password after after password expired, system will allow the user to login for 7 days with warning.

# usermod -f 7 sagar

Set sagar’s initial group as infra

# usermod -g infra sagar

Set the new password for the sagar

# usermod -p $3$32d

Set BASH as default login shell for the sagar.

# usermod -s /bin/bash sagar

Lock the user’s password

# usermod -L sagar

Unlock the user’s password

# usermod -U sagar

4. groupadd

groupadd command is used to create new group.

Create a new group on the system.

# groupadd sales

5. last

last command is used to show list of last logged in users.

List all entries

# last

Show who were all logged through tty2

# last tty2

Show the all entries of Jim user

# last Jim

Display only last 7 entries

# last -7

Hide the Host Name field from output.

# last -R

Show hostname field in last column.

# last -a

Display the IP Address of Remote Host.

# last -i

List all entries up-to Aug 18 12:00:00 2016

# last -t 20160818120000

6. lastb

lastb command is used to display a list of recent bad login attempts ” from /var/log/btmp log file “.

The syntax for lastb is same as useradd but the login given is for an already existing user. Below are the some commonly used options.

• -d : Change the user’s home directory.
• -c : Update the comment for the user.
• -g : Change the user primary group.
• -a -G : Add the user to one or more supplemental group.
• -G : Change the supplemental groups to only the list of groups and remove any other supplemental groups.
• -s : Change the default shell for the user.
• -u : Update the user’s UID number.
• -L : Lock the account by disabling the password.
• -U : Unlock the account and re-enabling its previous password.

I hope this article will help to learn some basic Linux command. If you have any queries and problem please comment in comment section.

Thanks:)