Have an iMac here roughly 2 years old and within the last week the admin account password has stopped working. It is the correct password, used on all of our devices and only IT staff use it. The password has not been changed. (our users use network accounts which have also stopped logging in, however that seems to be a network related issue as other computers are also experiencing this).
I have since attempted to enter internet recovery mode to either a) reset the admin password, or b) reinstall OS X (I believe it is running Yosemite). Both of these I have seen as options to get around the faulty password check.
However, upon booting into recovery mode, I am presented with an exclamation mark over a world icon and the following: apple/support -3001f.
I cannot find a description of this error anywhere. A few for -1006f or -1007f but absolutely zilch for -3001f.
What options to regain control of this Mac exist?