Linux Classroom Series – 24/Jul/2020

Users and Groups in Linux

• Linux is a multi user operating system.
• To add a new user account, we have two commands
  • adduser
  • useradd
• Generally whenever a user is created, User gets
  • username
  • uid
  • home directory
  • A group is created for the user with the same name as username
• Difference between useradd and adduser

adduser test1
useradd test2
cat /etc/passwd
ls /home

• Lets look at redhat
• we can set the password to the user by executing

passwd

• In the home directory, few hidden files are created
• If you look into /etc/passwd the entry pattern in this file looks as

[username]:[x]:[UID]:[GID]:[COMMENT]:[HOMEDIRECTORY]:[Defaultshell]

# ubuntu entries
test1:x:1001:1001:,,,:/home/test1:/bin/bash
test2:x:1002:1002::/home/test2:/bin/sh

• If you look into /etc/group file, the format for each line

[Group name]:[Group password]:[Gid]:[Group members]

# sample ubuntu entries
test1:x:1001:
test2:x:1002:

• For group management

groupadd
groupdel
usermod

• Exercise:

  1. Create a user called as ironman
  2. Create a user called as thor
  3. Create a user called as hulk
  4. create a user called as superman
  5. Create a user called as batman
  6. Create a user called as wonderwoman
  7. create a group called as Avengers and add ironman, thor and hulk to it
  8. Create a group called as JusticeLeague and add superman, batman and wonderwoman.
  9. Some screenshots

• How can i give sudo permissions to my users

  • In ubunutu we have a group called sudo, if you add users to this sudo group, then can execute sudo commands.
  • In RHEL family, we have a group called as wheel, adding users to this wheel group can enable users to execute sudo commands

• Adding a user ironman to sudo group