On Linux or AIX systems you might experience the following error while running the DB2 setup.
DBI20043E DB2 failed to install because of restrictive permission settings on the temporary directory /tmp
In the db2setup script there is a test for -noexec mount on the /tmp
As a workaround you could set the DB2TMPDIR to a different directory with proper perimissions if remounting /tmp with the correct permissions are not possible