How can I see Bash history from more than one terminal session in Ubuntu?

You can use

history -a

to immediately append the in-memory history to the history file. One terminal session can't see another's unless this is done or the other is exited.

You can use

history 200 | less

to see that number of entries.

In addition to HISTSIZE see the entry in the Bash man page concerning HISTFILESIZE.

Once you log out the history gets appended to the file ~/.bash_history. Have a look in there.

By default it will remember your last 500 commands. If you want to save more set the variable HISTSIZE in ~/.bashrc.

I also do add ignoredups to HISTCONTROL (with HISTCONTROL=$HISTCONTROL:ignoredup). This makes duplicate consecutive commands to be save only once.

Have a look at man 1 bash for what else you can tune about the history.

bash history is usually loaded when the shell begins running, and is saved when it is exited normally. You can use history -a and history -n to override this, but not automatically unless you abuse $PROMPT_COMMAND or something similar.

Sanoj, this really should "just work"; I don't think there is supposed to be anything special you need to do to enable this. It sounds like something is interfering with the normal course of events.

I would look in /etc/profile, /etc/bashrc (or perhaps /etc/bash.bashrc according to some sources), ~/.bash_profile, ~/.bashrc, ~/.bash_login, ~/.bash_logout, to see if there is anything that might be affecting the history (perhaps grep -i hist on each of the above files).

... In particular I wonder if you have something in ~/.bash_logout that removes the file.

Alternatively, is it possible that something is overriding the $HOME variable?