Difference Between Ubuntu Server and Ubuntu Server Live

The biggest differences you'll see are package manager, and package age.

Configuration files for apache, mysql/postgresql, php, etc are going to be in pretty much the same place, and as easy to find in either distro. There isn't crazy-customization in either ubuntu/debian or CentOS's config files for these things.

What will be different..

Package managers: Ubuntu & Debian use apt-get and dpkg. CentOS/RHEL uses yum and rpm.

Package age: Ubuntu is going to have the newest packages. Risk averse sysadmins often avoid it for that reason.

CentOS/RHEL has older, but very solid packages. Never bleeding edge, but rarely moldy.

Debian is going to have really old packages. Risk averse sysadmins often love it, because it's really, really, stable.

Even if the ubuntu tutorials will be for a different version of a package your using, you should still be able to follow it, just keeping in mind to replace "apt-get install php" with "yum install php", and things like that.

.bash_profile and .bashrc are specific to bash, whereas .profile is read by many shells in the absence of their own shell-specific config files. (.profile was used by the original Bourne shell.) .bash_profile or .profile is read by login shells, along with .bashrc; subshells read only .bashrc. (Between job control and modern windowing systems, .bashrc by itself doesn't get used much. If you use screen or tmux, screens/windows usually run subshells instead of login shells.)

The idea behind this was that one-time setup was done by .profile (or shell-specific version thereof), and per-shell stuff by .bashrc. For example, you generally only want to load environment variables once per session instead of getting them whacked any time you launch a subshell within a session, whereas you always want your aliases (which aren't propagated automatically like environment variables are).

Other notable shell config files:

/etc/bash_profile (fallback /etc/profile) is read before the user's .profile for system-wide configuration, and likewise /etc/bashrc in subshells (no fallback for this one). Many systems including Ubuntu also use an /etc/profile.d directory containing shell scriptlets, which are . (source)-ed from /etc/profile; the fragments here are per-shell, with *.sh applying to all Bourne/POSIX compatible shells and other extensions applying to that particular shell.