Pierre, many thanks for your help. I think I might need a compat-glibc for the "n-2 distro" as linuxthreads support was removed from Centos5; from the RHEL-4 release-notes: "support for LinuxThreads still exists for RHEL 4, ...advance notice that Red Hat Enterprise Linux 5 will no longer include support for LinuxThreads. Thus applications that require LinuxThreads support must be updated before they will be able to work properly on a Red Hat Enterprise Linux 5 system." In RHEL4 the solution was to one of the following: 1) Use LD_ASSUME_KERNEL environment variable or 2) Use an explicit rpath to /lib/i686/ or /lib/ to select LinuxThreads instead of NPTL at runtime I used solution #1 to get InsightII to run under Centos4. Is there any (reasonable) chance of providing older (=Centos3) libraries under Centos5 for one errant program? Thanks again for your time Jake Pierre Bourgin wrote: >Depends which older version you need; the compat-glibc package provides >binary compatibility with the n-1 distro: >Jake Grimmett wrote: >> 1) Some of our software needs linuxthreads (i.e. InsightII) but it's closed >> source and the writers (Accelrys) are unlikely to respin the code as they >> want us to move to a different program. -- Dr J. Grimmett Computer Systems Manager Division of Molecular Structure National Institute for Medical Research The Ridgeway Mill Hill London, NW7 1AA