How to change the bash prompt?

Question

When I open a shell, I get as prompt:
user@myhost:~$
Maybe it comes from my former Debian installation (I kept /home when installing Arch), because:
$ echo $PS1
${debian_chroot:+($debian_chroot)}\u@\h:\w\$
When I su to root, I get:
bash-3.2#
What do I have to do in order to get something like:
root@myhost:/home/user#
Browsing the Internet, I found that it has to do with /etc/profiles, but I did not manage to find out the specific steps.
Thank you.

Answer 1

Well, I renamed .bashrc (in order to keep it as a backup) in my home folder and then I got the bash-3.2$ prompt. For some reason, the PS1 in /etc/profile.bash is not taken.
If I just su, I got bash-3.2#. If I "su -", I got [root@myhost ~]#. Hypothesis: /etc/profile.bash is only observed by the root environment. May this be right?
So I edited the .bashrc that Debian had left, and I had to place it both as /home/user/.bashrc and /root/.bashrc. I copy it at the end. See that I made the prompt coloured when being root.
Still, if I did "su -" or "su username -", or logged-in in text-mode as root, I got the profile that is on /etc/profile.bash So I renamed /etc/profile.bash and copied that same file /root/.bashrc as /etc/profile.bash. I hope not to have committed any insanity , otherwise please let me know.
Thank you.
# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples
# If not running interactively, don't do anything
[ -z "$PS1" ] && return
# don't put duplicate lines in the history. See bash(1) for more options
export HISTCONTROL=ignoredups
# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize
# make less more friendly for non-text input files, see lesspipe(1)
[ -x /usr/bin/lesspipe ] && eval "$(lesspipe)"
## set variable identifying the chroot you work in (used in the prompt below)
#if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then
# debian_chroot=$(cat /etc/debian_chroot)
#fi
# set a fancy prompt (non-color, unless we know we "want" color)
#case "$TERM" in
#xterm-color)
# PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
# PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
#esac
# Comment in the above and uncomment this below for a color prompt
#PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
## If this is an xterm set the title to user@host:dir
#case "$TERM" in
#xterm*|rxvt*)
# PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME}: ${PWD/$HOME/~}\007"'
#esac
# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.
#if [ -f ~/.bash_aliases ]; then
# . ~/.bash_aliases
#fi
# If id command returns zero, you've root access.
if [ $(id -u) -eq 0 ];
then # you are root, set colour prompt
# see codes for colours on http://bash-hackers.org/wiki/doku.php/scripting/terminalcodes
PS1="\\[$(tput setaf 5)\\][\\u@\\h:\\w]# \\[$(tput sgr0)\\]"
else # normal
PS1="[\\u@\\h:\\w]$ "
fi
# enable color support of ls and also add handy aliases
if [ "$TERM" != "dumb" ]; then
eval "`dircolors -b`"
alias ls='ls --color=auto'
#alias dir='ls --color=auto --format=vertical'
#alias vdir='ls --color=auto --format=long'
fi
# some more ls aliases
#alias ll='ls -l'
#alias la='ls -A'
#alias l='ls -CF'
# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if [ -f /etc/bash_completion ]; then
. /etc/bash_completion
fi