I factory reset my M1 MacBook and it still contained the systems old hostname

Question

I followed this article to factory reset my device https://support.apple.com/en-us/HT212749

The article itself basically says to factory reset using this method before selling your computer. I did it. Gave the computer to my friend, my friend created a new account. Opened up terminal and now he sees friend@Coltons-Air.

Should I be worried about any other info being left there?

Answer 1

This is unlikely to be a security issue, nor any issue with data retained on the machine. Terminal shows the DNS name provided by the network if your friend hasn’t overridden the default setup.

Instead, what is happening is that the router that your friend is using is remembering the old cached hostname of your computer Coltons-Air, and it is assigning it to the computer.

If you performed the “Erase All Content and Settings” from the Apple article, then your machine has been factory reset, with no data retained.

Check out this other post for more details for a similar person concerned about wrong identity in the terminal app. For reasons, Apple made the shell (bash or zsh typically) to use what the router stored for the last computer seen and not use the name of the Mac connecting. To fix this:

sudo scutil --set HostName 'not-Coltons-Air'

Answer 2

You need to change HostName, ComputerName and LocalHostName.

Changing HostName alone will not solve this issue.

Just to add onto Scot’s answer, yes Hostname is associated to the router value. But if you really want to clear out any reference to the old names you need to change three different, yet seemingly similar, settings: They are HostName, ComputerName and LocalHostName and you can run the commands as follows; just change yourHostName to whatever you want to set them to.

sudo scutil --set HostName 'yourHostName'
sudo scutil --set ComputerName 'yourHostName'
sudo scutil --set LocalHostName 'yourHostName'

The breakdown of each setting is this; details courtesy of this post on OSXdaily:

• HostName: The name assigned to the computer as visible from the command line, and it’s also used by local and remote networks when connecting through SSH and “Remote Login.”
• ComputerName: The so-called “user-friendly” computer name for a Mac, it’s what will show up on the Mac itself and what will be visible to others when connecting to it over a local network. This is also what’s visible under the “Sharing” preference panel.
• LocalHostName: The name identifier used by Bonjour and visible through file sharing services like AirDrop.

So yes, the router caching plays a role, but macOS stores three different, yet related, “hostname” values in the system. You must change all three to be assured any remnants of past values are gone.