General form:

.nodeset v(nodnum)=val v(nodnum)=val ...
.nodeset all=val

Examples:

.nodeset v(12)=4.5 v(4)=2.23
.nodeset all=1.5

The .nodeset line helps the program find the DC or initial transient solution by making a preliminary pass with the specified nodes held to the given voltages. The restrictions are then released and the iteration continues to the true solution. The .nodeset line may be necessary for convergence on bistable or a-stable circuits. .nodeset all=val allows to set all starting node voltages (except for the ground node) to the same value. In general, the .nodeset line should not be necessary.