Why did you experienced boss suddenly leave? It may be a tell-tale sign of something more.
Inventory is great, learning everything on how to fix stuff is super, but that is what staff is for. How many individuals are reporting to you, or is that just the case, you are going to be the only individual in that department now, they pay you less and ask for me.
I would figure out first why the departure, second what does acting mean and they expectations the company has of you and what they had of the previous manager. Did you think he was doing a great job? What did you feel he was doing wrong? What was he doing right?
Figure out, if you want this role? Just because they gave it to you doesn’t mean you have to take it or want it. Is the pay adequate, what are their conditions to remove active from your title? Can you hire your replacement role immediately?
I wouldn’t worry so much about when a disaster strikes what do you do, because a) they don’t or shouldn’t expect you to know everything right away and b) you can’t learn the things that you don’t know so quickly and excel in this new managerial role
Managers/Directors/Heads of the Department are not going to know everything, the primary focus and why you are there is to hire those who do have knowledge beyond yours and create a synergy within your department that allows the best from the IT dollars spent in the company. If you think you are going to know everything and learn it yourself and work on every project and problem, wrong!
You have to find and depend on your employees with confidence and they will do the same in return. Be smart, don’t let them think you know everything about the system, even if you do, otherwise it is a long road ahead for you after you’ve raised your own bar. Obviously this was an abrupt decision somewhere because they didn’t have a replacement for you boss. Stabilize your position as becoming the manager and showing leadership first and foremost. If something breaks, become the hero by working on it overnight with diligence and getting it back up and running, they will reward you for that. Don’t make to many changes until you have secured your position and the acting title has been removed. Don’t push for changes either unless pushed, and the very last important rule…
Do not ever speak badly about your previous supervisor, even if someone else does. Just come up with a line that states, I’m not certain of his reasons for his choices at that time, however, I have a suggestion that I would like to present!
Good luck and congratulations!