Henry E. Outlaw, Jr., filed a pro se petition in the nature of mandamus in the District Court seeking credit on his federal prison sentence for time spent in state custody because a federal detainer allegedly prevented him from being released on bail on state charges pending against him. The District Court denied relief on the grounds that the claim should have been presented to the sentencing court in a motion to vacate pursuant to 28 U.S.C. § 2255. 1 This ruling was erroneous because the relief sought can be obtained either by a Section 2255 motion filed in the sentencing court, e. g., United States v. Morgan, 5 Cir., 1970, 425 F.2d 1388, or by petition for a writ of mandamus filed in United States District Court in the district of confinement, e. g., Ballard v. Blackwell, 5 Cir., 1971, 449 F.2d 868; Davis v. Attorney General, 5 Cir., 1970, 425 F.2d 238.

Accordingly, the District Court’s judgment dismissing the complaint is vacated and the cause is remanded to the District Court for further proceedings, including an evidentiary hearing if necessary, followed by entry of appropriate *1258 findings of fact and conclusions of law on the issues presented by Outlaw’s petition.

Finally, the record shows that Outlaw failed to properly serve the United States with a copy of summons and of the complaint in this matter. The United States Attorney represents that he had no knowledge of the proceedings until February 28, 1972, after this appeal had been docketed in this Court, even though judgment had been rendered in favor of the United States. On remand, the District Court should afford appellant a reasonable period of time to effect proper service on the United States in accordance with Rule 4(d)(4), Federal Rules of Civil Procedure.

Vacated and remanded.