runInstaller
It follows evidences :
$ id
uid=207(oradxi) gid=202(dba) groups=201(oper)
drwxrwxrwx 17 oradxi dba 4096 Sep 28 10:25 oracle
drwxrwxrwx 19 oradxi dba 4096 Sep 28 12:17 DXI
drwxrwxrwx 6 oradxi dba 256 Sep 28 12:26 tmp
drwxrwxrwx 2 oradxi dba 256 Sep 28 12:19 OraInstall2009-09-28_12-19-20PM
drwxrwxrwx 2 oradxi dba 256 Sep 28 12:24 OraInstall2009-09-28_12-24-53PM
drwxr-xr-x 2 oradxi dba 256 Sep 28 12:25 OraInstall2009-09-28_12-25-23PM
drwxr-xr-x 2 oradxi dba 256 Sep 28 12:26 OraInstall2009-09-28_12-26-49PM
export TEMP=/oracle/DXI/tmp
export TMP=/oracle/DXI/tmp
$ runInstaller -ignoresysprereqs
Starting Oracle Universal Installer...
Checking installer requirements...
Checking operating system version: must be 5200 or 5100
Failed <<<<
>>> Ignoring required pre-requisite failures. Continuing...