A sealing device for sealing a positive or negative pressure zone of a roll for a machine for producing or processing a fibrous web includes a sealing strip and a lubricating device for introducing a lubricant between an inner surface of a roll shell and a sealing surface of the sealing strip when used as intended. The lubricating device includes a plurality of lubricant outlet openings and can be connected to a supply line for supplying lubricant. The lubricating device can be connected to the supply line through a plurality of inlets which are distributed over the length of the sealing strip. The sealing strip has a first and a second longitudinal-side end and the distance from at least one longitudinal-side end, preferably both longitudinal-side ends, to an inlet is at most 800 mm. A roll and a method for operating a roll are also provided.