A few settings to be put into the .bashrc.

Ignore duplicates in history, but do put in comands that start with spaces:

HISTCONTROL=ignoredups # (default: ignoreboth)

Keep a lot of history:

export HISTSIZE=10000  # default: 1000
export HISTFILESIZE=10000  # default: 1000

When the shell exits, append to the history file instead of overwriting it:

shopt -s histappend 

Disable the annoying password thingy in KDE:

unset SSH_ASKPASS