While trying to upgrade Nexus 5000 series switch I ran into following issue:

Pre-upgrade check failed. Return code 0x40930062 (free space in the filesystem is below threshold).

Switch has enough free:

Enough free space

Look at install logs to identify where the problem is by typing:
show system internal log install details | include space

show system internal log install details | include space

As you can see the problem is because /var/tmp is bellow the threshold.
To identify what is  taking space in /var/tmp type:
show system internal dir /var/tmp (more…)