History of bash sessions are stored in the RAM and written back to ~/.bash_history when the user logs out of the bash session.

To delete the bash history

1. Delete the .bash_history file.

rm -rf ~/.bash_history

2. Clear the current history stored in RAM.

history -c

Stop logging the bash histories

Turn off bash history for all users

Append unset HISTFILE to /etc/profile.

echo "unset HISTFILE" >> /etc/profile

Turn off bash history for a specific user

Append unset HISTFILE to /home/<username>/.bash_profile.

echo "unset HISTFILE" >> ~/.bash_profile