Re: su(substituting user) in linux

[Bob Proulx]

kuldeep vyas wrote:
> I'm using Redhat 9 (kernel 2.4.20-8 on i686)
> I logged in as k(username), then I started terminal, &
> then I gave following commands
> [...abbreviated case follows...]
> k>su
> root>su k
> k>su
>          // now after giving password I don't get a   
>             response from terminal

I tested this in a RH9 chroot area on my Debian machine.  Although the
command did not hang I was able to create a noticeable delay at that
point.  Most curious.  I actually thought that it did hang but then
while I was trying to determine what it was doing and some time had
past the command did continue to a prompt.  It surprised me because I
did not expect that.

But coreutils-4.5.3 as shipped with RH9 is rather old now.  I tried
this on a RHEL4 machine with a much newer version of su and could not
recreate the problem.  I can only believe that this problem, whatever
it is, has already been fixed in a later version of the command.

Thank you for your report.  However I don't think there is anything
more that can be done because newer versions do not exhibit this
behavior.  If you wished to dig into this further you could pull the
source code to the version you are running and debug into it further
on your machine and let us know the results.  Or you could upgrade to
a newer version of the command which seems to have this problem fixed
already.  Here is the location of the current code.

STABLE
  ftp://ftp.gnu.org/gnu/coreutils/coreutils-5.2.1.tar.gz
  ftp://ftp.gnu.org/gnu/coreutils/coreutils-5.2.1.tar.bz2

BETA
  ftp://alpha.gnu.org/gnu/coreutils/coreutils-5.91.tar.gz
  ftp://alpha.gnu.org/gnu/coreutils/coreutils-5.91.tar.bz2

The current daily CVS of the source code is available from savannah.

  http://savannah.gnu.org/cvs/?group=coreutils

> If I exit from my first su (of root),then everything
> is OK, but why I'm not allowed to substitute user as &
> when required. Is it a bug or my approach of
> substituting user is not correct?

I think what you are doing is fine.  Although it is a little unusual.
The 'su' command is very system specific however and there has been
discussion of moving it out of coreutils and into a hostutils
package.

Bob