PATH nfg after su

[Bob Bernstein <poobah@ruptured-duck.com>]

Here I've been sailing along blissfully unaware that when on 
those rare occasions I execute su in a terminal, say to tweak my 
exim4 config, that I had a pretty much useless PATH in the env 
after su-ing:

PATH=/home/bob/bin:/usr/local/bin:/usr/bin:/bin:/usr/games

So I could not, say, execute 'service exim4 restart'. (But 
systemctl was available because /bin was in PATH.)

The above-mentioned blissful unawareness fostered my delusion 
that 'su' in bash loaded the contents of /etc/profile.

But enough about me. Obviously my login process is hosed 
somewhere, no doubt the result of years of bringing this box 
along to its current buster status.

Thoughts? All suggestions will be much appreciated. (I can even 
accept a bit of abuse if that is required of me.)

Thank you.

--
 A test of right and wrong must be the means, one would
 think, of ascertaining what is right or wrong, and not a
 consequence of having already ascertained it.

                                  J. S. Mill