Changing groups

The chgrp command will be discussed now in the context of making packtgroup the new owner of testfile. After the command, we specify the name of the group and the name of the file whose ownership is to be changed (in this case, testfile):

sudo chgrp packtgroup testfile

Let’s check the ability of user packtdemo to write to this file now. A permission refused error should appear for the user. We can set the relevant permissions for the group to allow packtdemo to write to the file:

sudo chmod g+w testfile

Then use usermod once more to add the account to packtgroup, this time using the -aG combined option as follows:

sudo usermod -aG packtgroup packtdemo

The abbreviation for append to group is -aG.

Currently, packtgroup is referred to as a subsidiary or auxiliary group for user packtdemo. When packtdemo next logs in, the updated access permissions will be active.

We can use chown followed by the usernames and filenames, in that order, to...