How to create two users who can read files of each other?

Question

How to create 2 users a and b from shell, that will be able to read files of each other( say a can read the files of b, and b can read the files of a) .

sudo adduser newuser
sudo passwd newuser

Answer 1

The classic way to do this is to make sure that both users belong to the same group. Then, you change the ownership of their files to that group. So, for example, to create bob and alice and allow them to read each other's files:

1. Create the group that both users will belong to

   sudo addgroup users
   

2. Create the users, setting users as their primary group

   sudo adduser --ingroup users alice
   sudo adduser --ingroup users bob
   

That's it. Now, any files created by alice or bob will belong to the users group and since both users belong to that group, they will both be able to read them:

alice@foo $ echo "hello" > ~/file
alice@foo $ ls -l file
alice@oregano ~ $ ls -l file 
-rw-r--r-- 1 alice users 6 May 11 16:12 file

and

bob@foo $ cat ~alice/file
hello

Answer 2

In a terminal (xterm is OK) execute cat /etc/group to obtain a list of available groups in your system; to add a custom group execute sudo addgroup group_name with a name of your choice.

Create the two users with the command you've written, then go to the directory with your files and execute sudo chgrp file or chown :group file to change their group to the one you've chosen before. After assign both users to the same group of the files with sudo usermod -a -G group username; this will not alter the existing assigned groups, don't worry.

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