Permissions and User management

Change group ownership

The code below will associate a folder to a specific group. This is helpful when you are associated with more than one groups and the default group assigned to a file you created is not for the intended group.

chgrp -R new_group path/to/folder
# R for recursive

Ensure the group ownership and permissions of the target directory are properly set if multiple users in the gemini group need access. For example, to make all new files inherit the gemini group:

chmod g+s /path/to/folder

Recursively change a folder's ownership

chown -R <owner>:<group> <directory>

File permissions using chmod

The code below will give read, write, and execute permissions to all the group members. A minus sign after g e.g. g-wx will take away write and execute permissions.

chmod -R g+rwx path/to_folder
# R is for recursive

Add a new user

The command below will add a new user to a Linux system, create their home directory at /home/newuser and set the default shell to /bin/bash.

sudo useradd -m -s /bin/bash newuser

The command below set the password for the new user.

sudo passwd newuser

List all the users that have a home directory

awk -F: '/\/home/ {print $1}' /etc/passwd

Delete a user

The command below will delete a user without deleting their home directory.

sudo userdel newuser

To delete the home directory as well.

sudo userdel --remove newuser

To login as a newly created user

sudo -u newuser bash

# or

su newuser

List all the groups that a user belong to

groups user

Add an existing user to a group

sudo usermod -a -G groupname newuser