Why does su change PATH on amd64 but not on hurd-i386 ?

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

i guess it is not intentional that on a freshly installed Debian GNU/Hurd
  $ su
  Password:
  # apt-get install libacl1-dev
fails with
  ...
  Get:2 http://jk.fr.eu.org/debian/hurd-installer/mirror/ sid/main libacl1-dev hurd-i386 2.2.47-3 [78.1 kB]
  Fetched 119 kB in 0s (373 kB/s)       
  dpkg: warning: 'ldconfig' not found in PATH or not executable.
  dpkg: warning: 'start-stop-daemon' not found in PATH or not executable.
  dpkg: error: 2 expected programs not found in PATH or not executable.
  Note: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin.
  E: Sub-process /usr/bin/dpkg returned an error code (2)
  #

PATH looks like inherited from my normal user.
  # echo $PATH
  /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/home/thomas

On the hosting Debian GNU/Linux amd64 i see
  $ echo $PATH
  /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/home/thomas
  $ su
  Password:
  # echo $PATH
  /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

The same i get if i login to Hurd at the kvm console without
intermediate user "thomas". 


So what shell setup script is run on am64 but not on hurd-i386 when
command su is performed ?
It is not /etc/profile, where i can see the root PATH, but where i
cannot cause any visible side effects by running su.
(I edited /etc/profile and inserted the line
   echo Executing amd64 /etc/profile : $(/bin/date) >>/tmp/profile.log
 It gets not performed on su.
)


Have a nice day :)

Thomas