Where are ALL ubuntu logs/terminal history stored

There are a lot of places where things get logged, and it will be very diffucult to be exhaustive, depending on what applications you use. That said, here are the main places I can think of:

• most system logs go into /var/log
• firefox stores your history, cookies, etc... in ~/.mozilla/firefox This can be purged from Firefox (shift+ctrl+suppr)
• zeitgeist is an history daemon, that populates the dash recent history. It can be purged from the privacy settings
• terminal command history is saved on a per-user basis in ~/.bash_history Deleting this file will remove this history.
• gnome applications (gedit, nautilus, etc...) store recently used files in ~/.local/share/recently-used.xbel This file can be deleted if needed.

These are the main places I can think of, but any application can log things in various places... so it really depends on what logs you want to remove.

As mentionned by MrVaykadji, BleachBit is a GPL software that automates such cleansing task, and let you delete "log files" for a wide variety of known softwares. You can also easily add new cleaners with simple xml files. Might be what you are (ware) looking for!

It is located in: ~/.bash_history

Your bash history file is in your home directory: /home/your-user-name/.bash_history

Zeitgeist user history is stored in ~/.local/share/zeitgeist.

To reset the Zeitgeist history, open a terminal and copy/paste the following commands:

rm ~/.local/share/zeitgeist/activity.sqlite

Or navigate to that directory in Nautilus or your file manager and manually delete the sqlite database "activity.sqlite". It will be created again by Zeitgeist minus your previous user history.

I do not feel comfortable telling users to use some commands unless they understand the command completely and are careful to double check that the command is written correctly, especially any command beginning with rm since a user could easily do irreparable damage to their system if the command was incorrectly formatted, but to better answer the OP's question as suggested in comments, the system logs are stored in var/log But I have heard of people causing problems by deleting subdirectories inside the log directory as is mentioned here Can I delete /var/log files due to low root space?

But keep in mind that if you need to troubleshoot some system problem the logs will be very useful.

You can delete the contents of the journal folder by opening a terminal and copy and paste the following command:

sudo rm /var/log/journal/*

To see how much space it is using on your computer you can open a terminal and issue the query:

journalctl --disk-usage

My system is currently is using 3.9GB.