Years ago, I remember RedHat already provided /etc/bashrc.d/ to add custom scripts to be sourced site-wide whenever bash was started. Debian still only provides /etc/profile.d for such scripts. So, back in the days I started using Debian, I added stuff in this latest directory and made sure that /etc/bash.bashrc itself ran /etc/profile so it would be sourced in any cases.
There is actually a problem with that.
As defined (RTFM! `man bash`), /etc/profile is to be sourced for interactive login shells (`bash –login`) while /etc/bashrc or /etc/bash.bashrc is to be sourced for interactive non-login shells (`bash`). Having /etc/profile ran by /etc/bash.bashrc defeats the overal purpose of distinguishing the two of them. LFS ask for /etc/profile content to be a run-once thing, for logins, not something that should be started for any xterm.
But if you don’t, anything in /etc/profile.d will be ignored by most shells you’ll start on a X session, where you actually log in once and then starts numerous xterms. Ok, to put your aliases and local functions, you can edit /etc/bash.bashrc and use skels for ~/.bashrc, but that’s way less convenient than just copying a script into a directory.
To get something consistent, I added the /etc/bashrc.d directory. I think such directory should exists by default on Debian, even if I would agree if someone was to point out that this should not be BASH-specific.
[ -z "$ETC_BASHRC_SOURCED" ] && for i in /etc/bashrc.d/*.sh ; do if [ -r "$i" ]; then . $i; fi; done
Note that the same postinst script symlink /etc/profile.d/bash_completion.sh to /etc/bashrc.d/bash_completion.sh. The very existence of this file in /etc/profile.d IMHO show the extent of the broken default design. How come someone would actually want bash completion for login shells but not for interactive non-login shells? I would actually expect the contrary: as bash completion can be CPU time consuming, if it is to be skipped in only one case, it’s definitely on login shells! Why is it so? Probably because only /etc/profile.d exists.
(I’ve read also some people saying that /etc/bash.bashrc should be edited by hand. On any computers of a local network just to add a few local aliases? Ouch!)