I always forget to use the admin db when copying that line. It should say something like db.getSisterDB('admin').$cmd.sys.unlock.findOne()

rs:PRIMARY> db.adminCommand(

{fsync:1, lock:1}

)

{ "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock", "ok" : 1 } rs:PRIMARY> db.$cmd.sys.unlock.findOne() { "err" : "unauthorized" }

rs:PRIMARY> use admin
switched to db admin
rs:PRIMARY> db.$cmd.sys.unlock.findOne()

{ "ok" : 1, "info" : "unlock requested" }