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Linux Users, Groups, Permissions

Add new user:

useradd -m -G wheel -s /bin/bash username
passwd username

Give sudo permissions:

make sure you have sudo installed and if it doest work try:

EDITOR=vim visudo

add user to group:

sudo usermod -aG google-sudoers username

SUDO

sudo -i

sudo useradd -m llmaicode
sudo passwd llmaicode

su - llmaicode
su - alice

https://www.debian.org/distrib/

authorized_keys

i am on debian and i am just about to give someone i don't trust access to my computer with user privilges how to make it so that i can see all actions they do, accept or reject their sudo request per notification have a snapshot before they got access to role back and see diff what they added after snapshot for audit

i guess qemu vm with kvm i will do to have it more isolated and code as infra or setup reproducable and the stuff you say just give me all commands i need to do to install and setup and thne makefile and other setups

1) Users​

See users​

  • whoami → shows current user
  • id → shows user ID (UID), groups, and group IDs
  • cat /etc/passwd → list all system users

Create / modify users (admin required)​

  • sudo useradd username → create user
  • sudo passwd username → set password
  • sudo usermod -aG groupname username → add user to group
  • sudo userdel username → delete user

2) Groups​

View groups​

  • groups → groups of current user
  • groups username → groups of another user
  • cat /etc/group → all groups

Manage groups​

  • sudo groupadd groupname → create group
  • sudo groupdel groupname → delete group
  • sudo usermod -aG groupname username → add user to group

3) Permissions (core concept)​

Each file has:

  • Owner (user)
  • Group
  • Others

Check permissions:

  • ls -l

Example output:

-rwxr-xr--

Meaning:

  • r = read
  • w = write
  • x = execute

Breakdown:

  • rwx → owner
  • r-x → group
  • r-- → others

4) Changing permissions​

  • chmod 755 file
  • chmod 644 file

Meaning:

  • 7 = rwx
  • 6 = rw-
  • 5 = r-x
  • 4 = r--

5) Changing ownership​

  • sudo chown user file
  • sudo chown user:group file
  • sudo chgrp group file

6) extras​

  • umask → default permission mask
  • sudo → run commands as admin
  • getent passwd → query system user database cleanly
  • Users = identity
  • Groups = shared access buckets
  • Permissions = what each bucket can do to files