One of the great selling points for Macs has been a combination of their longevity and resale value. I know many people with decades old Macs. For the past two decades, I've easily gotten seven or eight years of some Macs I've owned and then sold them to people who kept them in use.
There is a lot to consider when buying a used Mac to make sure it continues to work. But something you can overlook is that security decisions from previous owners could conspire to lock you out under certain circumstances. This can happen during a restart, when you try to delete and install MacOS, or even by logging in, depending on which state your Mac was left in when you purchased it.
The best way to buy a Mac is after the seller has deleted the drive and installed a fresh copy of macOS on it without completing the installation, so you can do it from scratch without worrying about software they may have installed or passwords or accounts they have created.
And the best scenario for receiving a used Mac is to make it personal, so you can look up your computer and see that it works, carry out the tests listed below, and make sure no extra is needed passwords or permissions.
No matter how you receive the Mac, check out these items, preferably before you terminate the agreement.
Turn your Mac down and perform a "cold boot" ̵
Start restart Usually from the Finder and hold down the -R command to be sure you can boot into MacOS Recovery. (If MacOS Recovery is not installed, the Mac should try to retrieve it over the Internet and install it. If a lock icon and a password field appear on its own, see the firmware password section below.)
In the recovery program, run Disk Utility. Can you mount the disk without a password? And run Disk First Aid to ensure no issues are reported.
It covers basics, but you can and should dig deeper. (You should also use this checklist before selling a Mac.)
Tip: If a seller bends by giving a password to you directly for something that can be entered while it is started in MacOS correctly – a perfect affordable thing to resist – you can use a little hidden feature for iMessages. In a chat session with Messaging for MacOS that has the blue bubbles showing an iMessage connection, click the Details button in the upper right and then the overlapping screen icon. Select Invite to share my screen. The seller can then enter the password remotely as needed. (They may and will probably change their iCloud or other password after that as well.)
Is one or more accounts created?
If someone else sets up a computer, you do not necessarily know what is running on it. I suggest deleting the drive and reinstalling MacOS via MacOS Recovery. However, if it is not an option or you are not worried, you must at least delete all unnecessary accounts and change the password on the master account, which must have administrator rights.
You should also be sure you keep any accounts that Mac is not logged into the seller's account in the iCloud preference panel.
Is a firmware password set?
A firmware password locks the Mac for booting only with a specific boot disk. This can be a problem later if you want to boot from a remote station or make other changes. Check this and remove or change the firmware password with these steps:
Restart the Mac and hold Command-R to start MacOS Recovery.
If you are prompted for a password next to a lock icon, you need the seller to give this firmware the password. Enter the password.
When the recovery starts, select Tools> Firmware Password Utility (older Macs and some newer models) or Tools> Startup Security Tools (Macs with T2 security chip), and then Turn of firmware passwords. When prompted, enter the password again.
If you want to keep the firmware password enabled, now click Turn on Firmware Password and enter a password you just know and that you register, preferably in a password management app.  Mac911 firmware password cannot change boot play "width =" 1200 "height =" 724 "data imageid =" 100801686 "data-license =" Supplied Art "/> Apple
If a firmware password is
If the seller does not have the password, it does not go fast, but it does not require them to participate to have the Mac unlocked, Apple says that the original receipt or invoice showing the purchase of the Mac required and the Mac must be brought in personally to an Apple Store or an authorized Apple supplier.
Is FileVault turned on?
FileVault encrypts the entire contents of a Mac drive, making the files unreadable when it is turned off There are terrific technologies that I strongly recommend to use, however, there are two types of problems with having it enabled when you buy a used Mac.
First, FileVault must be enabled on each account you want to log in. On a used one Mac prepared for you, d one should be a single account created with administrative rights. Because FileVault needs to be turned on for at least one account, that's all it takes. I suggest deleting other accounts created on the device and changing the password on this account.
Second, there is some kind of security utilization available if someone else creates FileVault. When you turn on the encryption, macOS generates a recovery key that allows you to decrypt a drive even if you do not have an account password. This can be given directly to the person who puts it up or stashed in an iCloud account as escrow.
The seller could and should give it the key to you. However, you should also reset FileVault encryption. Without the recovery key, you can be locked out. Or, if you don't buy a computer from someone who is a criminal, you might try to get it back later, they can decrypt the drive without your permission or password.
In Catalina, see Find My Mac
Apple extends the activation lock protection as it added more releases page to iPhones and iPads with MacOS 10.15 Catalina for any Mac with a T2 security chip. This chip offers the same "secure enclave" that makes Apple Pay, Touch ID and other features available on Mac as it has been on generations of iPhones and iPads.
With the enable lock turned on, you will not be able to delete your Mac and re-install MacOS. Check the activation by logging in to the main or one's account and watching the iCloud preferences – Is My Mac enabled?
If it is, it is bad from a few fronts, because it means that the seller shares another iCloud information with you, as well as the Mac is locked against future deletion. The seller should be entitled to ensure that the activation lock is disabled.
When you buy, the buyer remembers authorizing iTunes on a Mac before deleting or forwarding it to you. The iTunes Store has a limit of five computers for use with a single account, and you cannot authorize certain computers after they have deleted their drives even after you reinstall macOS.
You can deauthorize all computers that are associated with an iTunes account, and log back in to just the computers you want to keep in the set. You can only deauthorize all computers twice a year.
This Mac 911 article answers a question from Macworld reader Noah.
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