Adicione sua configuração PS1 modificada a /etc/profile.d/custom_ps1.sh . Arquivos sob /etc/profile.d são automaticamente originados de /etc/profile :
if [ -d /etc/profile.d ]; then
for i in /etc/profile.d/*.sh; do
if [ -r $i ]; then
. $i
fi
done
unset i
fi
O que é chamado sempre que um shell de login é gerado. Na bash manpage :
When bash is invoked as an interactive login shell, or as a non-interactive shell with the
--loginoption, it first reads and executes commands from the file/etc/profile, if that file exists. After reading that file, it looks for~/.bash_profile,~/.bash_login, and~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The--noprofileoption may be used when the shell is started to inhibit this behavior.