How to start over with Homebrew?-CodePudding

I recently replaced my Intel Macbook with an M2 Mac, using my Time Machine backup to initialize the hard drive. That, of course, dutifully copied all the Intel code.

I had brewed onto the old system. Today running brew upgrade gives me:

Error: Cannot install in Homebrew on ARM processor in Intel default prefix (/usr/local)!
Please create a new installation in /opt/homebrew using one of the
"Alternative Installs" from:
  https://docs.brew.sh/Installation
You can migrate your previously installed formula list with:
  brew bundle dump

So of course I ran brew bundle dump and that didn't give me any more direction. I'm ready to wipe the entire slate clean with something like rm -rf xxx and start over, but I feel like I should be choosy about xxx.

FWIW, brew --version returns:

Homebrew 3.6.5-10-gbde685a
Homebrew/homebrew-core (git revision d6fa8906828; last commit 2022-10-11
Homebrew/homebrew-cask (git revision 576798b72f; last commit 2022-10-12)

Any real help would be welcome (except "switch to macports").

CodePudding user response：

Don't rush to follow my advice, or accept my answer. Someone else may give you something better if you are patient...

You should be able to get a list of installed packages in the current setup then it'll be easier to install the same packages in the new one. Try this and see if it looks correct:

brew ls > ~/oldbrewpackages.txt

You need to find where your current casks and stuff are installed. Like this:

brew config

and look for HOMEBREW_PREFIX. Snuffle around in there and see if it looks like where all your packages are.

Next, I would look around for anything to do with homebrew in my login profiles, comment it out by putting a hash (#) at the start of the line, save the file and check you can still start a new Terminal without errors:

grep -i homebrew -/.*

Now, rather than removing all your homebrew stuff under HOMEBREW_PREFIX, I would try renaming it. You may need to turn off "System Integrity Protection" first.

Then if your homebrew stuff is under /opt/homebrew, you could do:

sudo mv /opt/homebrew /opt/homebrew.unused

Then you'll want to reboot.

Now you should be able to install a new homebrew without it detecting the old one... hopefully.

To install your previous packages in your new homebrew, you want:

brew install $(cat -/oldbrewpackages.txt)

If everything looks good and works well, make a backup and then type the command to delete your old stuff, and read it very carefully 3x before hitting Enter

sudo rm -rf /opt/homebrew.unused

CodePudding user response：

It turns out that just running "brew bundle dump" is only the first step. Follow that wit "brew bundle install --file Brewfile", as explained very clearly in earthly.dev/blog/homebrew-on-m1