runInstaller get /tmp wrong and won't run

 Hello All,
I'm trying to install the OEM agent on a machine. It seems to believe there isn't enough
tmp space, but there is loads:
$ df -k /tmp
Filesystem            kbytes    used   avail capacity  Mounted on
swap                 7380368    3048 7377320     1%    /tmp
$ ./runInstaller
Starting Oracle Universal Installer...

Checking installer requirements...

Checking operating system version: must be 5.8, 5.9 or 5.10.    Actual 5.8
                                      Passed

Checking temp space: 163 MB available, 250 MB required.    Failed <<<<
Checking swap space: must be greater than 500 MB.   Actual 13243 MB    Passed
Checking monitor: must be configured to display at least 256 colors.    Actual 16777216    Passed

Some requirement checks failed. You must fulfill these requirements before

continuing with the installation,at which time they will be rechecked.