An eigenvalue buckling analysis looks at the potential for buckling on a structure with a given load. Unlike a modal dynamic analysis, which characterises the structure, a buckling analysis characterises the structure for a given load.
In most cases a buckling analysis follows on from a linear static analysis, so a model set up for static analysis is the normal starting point. As buckling effects are three dimensional, it is inadvisable to define global restraints on the structure, as this can potentially provide an artificial degree of stiffness to the model.