Fatal error error writing to tmp No space left on device

[amunro]

I am trying to compile several programs to install on a VPS but I cannot write to the /tmp directory.

df /tmp shows this:

# df /tmp
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 1048576 620 1047956 1% /tmp


As the use is 1%, I don't understand why I cannot write to that directory.