Sometimes your /tmp directory may be mounted to a partition name overflow
and the size for this partition may be 1M ,while its a 100% full capacity.
This may happen if the root partition got full ,
and the system was in need for some space to operate.
to overcome this issue , you may just unmount the partition using
# unmount overflow
If you get an error saying the device is busy , you may also try unmounting the partition with the
Lazy unmount flag . Detach the file system from the file system hierarchy now,
and cleanup all references to the file system as soon as it is not busy anymore.
# unmount -l /tmp