As soon as I am starting the installation of Oracle 8.1.7 on Solaris 2.6, I am getting this error.

"Error in writing to directory /tmp/OraInstall. Please ensure that this directory is writable and has at least 25 MB of disk space. Installation cannot continue."

I tried removing the /tmp/orainstall dir and ran again but same error. I even tried changing the /tmp dir but then also I had the same error. I have enough space too.
Did anyone get this error ?