Migrate from Intel (Rosetta2) to ARM brew on M1

[tyron]

I noticed the progress on Homebrew/brew#10152 and that the installation script has been updated to install under the new /opt/homebrew prefix on M1 Macs. I had brew installed through Rosetta2 (/usr/local/homebrew) and running brew up && brew doctor now tells me:

Warning: Your Homebrew's prefix is not /opt/homebrew.

What is the best way to move from Rosetta2 to ARM on M1 Macs? Should I follow uninstall instructions + new installation?
Running brew upgrade displays:

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

But it's not clear what happens to the old installation... Does it get removed, do we need to handle 2 brew commands?

[carlocab]

The old installation stays there, allowing you to migrate it to the new brew installation at your convenience.

do we need to handle 2 brew commands?

Unless you uninstall your Rosetta 2 installation, yes. Don't forget to add /opt/homebrew/bin to your PATH.

[derekschinke]

I'm unable to access my old installation now. brew in both Terminal.app and Terminal Rosetta.app don't show anything as being installed after running brew bundle dump

[carlocab]

If /opt/homebrew/bin appears in your PATH before /usr/local/bin, then calls to brew will always be to your M1 installation. You need to access your Intel installation with /usr/local/bin/brew.

[kizzlebot]

So do we run rm -r /usr/local/Cellar or something similar to clean up the old installation? Is there a reason for preserving the old installation once we migrated to the m1 version of brew?

[carlocab]

You can use the uninstall script to uninstall your old installation. You'll want to download it first and run /bin/bash uninstall.sh --help as suggested in order to know how to specify the prefix you want to uninstall from. If you don't specify this, it will assume you want to uninstall the one in /opt/homebrew.

Is there a reason for preserving the old installation once we migrated to the m1 version of brew?

Some formulae don't work on ARM yet. The ones that do aren't all necessarily fully stable yet. So, you may wish to keep a Rosetta installation in the meantime.

[JakobJingleheimer]

By default on Big Sur (or possibly due to migrating from High Sierra via Time Machine), /opt/ is owned by user root and group wheel (root's group).

Is homebrew expecting a chown first? A bit of googling suggests there's no standard for who should own /opt/.

Relevance: the homebrew Alternative Installation instructions say to create a /opt/homebrew directory, which fails with Permission denied!.

[derekschinke]

same, brew bundle dump didn't transfer anything for me.

[SMillerDev]

No, it dumps the formula you installed to a brewfile so you can install that using the ARM based brew. It doesn't actually migrate anything.

[JakobJingleheimer]

That definitely wasn't clear…

thanks for the clarification though

[gromgit]

whilst running brew bundle dump, I encountered similar permission denied issues on /opt/. I temporarily changed the owner of /opt/ to work around them, but I suspect there might be more in future (since I changed it back after).

From the brew man page:

  brew bundle dump
      Write all installed casks/formulae/images/taps into a Brewfile in the current directory.

If you were in /opt when you ran brew bundle dump, that would explain your "permission denied" errors. If that wasn't the case, please post the exact error you saw.

also, bundle dump did not migrate any of my existing formulae (they are all still in /usr/local/).

The above extract from the man page explains why.

[JakobJingleheimer]

Yes, I was in /opt/ at the time (as per the instructions: mkdir homebrew, which would need the cwd to be /opt/). I was following the error message from homebrew that instructed me to reinstall it and then run the bundle dump to migrate my existing formulae (which it doesn't).

I realise homebrew's target audience is tech-savvy, but it could definitely benefit from a bit more hand-holding rather than a shove out of the nest.

Did I follow the instructions homebrew outputted? Yes.

Did it address the problem / did homebrew start working? No.

Did I have any idea what I was supposed to do next? Also no.

After the vague "go find X and then do Y", none what I expected to happen did. I started googling, and the most helpful thing I found was a snarky comment in a bug that explaining why the new install was not picked up (something was required to be added to .bash_profile, which the instructions didn't mention nor did the installation output, as erroneously claimed by the snarky poster), and this post with @carlocab's helpful insight (which I vote be added to brew.sh's alternate installation instructions, cuz they're definitely needed).

[pragyasresta29]

This is what worked for me. If /opt/homebrew is before /usr/local/bin/brew then it uses the homebrew of M1 installation. If /usr/local/bin/brew is before /opt/homebrew then it uses the rosetta installation.
My path in ~/.zshrc looks something like this:
export PATH=$HOME/bin:/opt/homebrew/bin:/usr/local/bin:$PATH
So, now when I use brew, it uses the M1 installation and doesn't show the error.
But the error now shows when I want to use the rosetta installation. I figured I just need to change the precedence of the path to use either one. For now, I use the homebrew for M1.

[NateLevin1]

You just saved my day. TYSM!

[avxkim]

is it safe to remove old brew installation at /usr/local?

[SMillerDev]

If you don't need anything from it, yes

[SaschaKo77]

What I did is running brew bundle dump as suggested by brew upgrade. This creates a file named Brewfile in the current directory. Then I installed the new version of brew for M1 in /opt/homebrew/. Finally adding /opt/homebrew/bin to the path (at the beginning) and running brew bundle --file Brewfile installed everything in the new brew environment.

[lilyharuna]

You just saved my life. You're a genius! Thank you a lot. I resolved my problems. :)

[nodesocket]

@SaschaKo77 Thanks for this comment, super helpful. I just got my MBP 16" M1 Max today and running zsh shell.

I've done:

# write a file with all existing brew packages out to Brewfile
brew bundle dump

# re-install Homebrew, will install into /opt/homebrew and use the arm version
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Any idea what I should set in .zshrc to use the new path for brew though? My brew is still using:

MacBook-Pro ➜  ~ which brew
/usr/local/bin/brew

Also, after I migrate all my packages from the Brewfile how can I completely uninstall the previous Intel version of Homebrew?

[nodesocket]

A helpful tip, to check if an executable is Intel or ARM you can use the file command like:

Intel

MacBook-Pro ➜  ~ file /usr/local/bin/git
/usr/local/bin/git: Mach-O 64-bit executable x86_64

Apple Silicon (ARM)

MacBook-Pro ➜  ~ file /opt/homebrew/bin/git
/opt/homebrew/bin/git: Mach-O 64-bit executable arm64

[gromgit]

Any idea what I should set in .zshrc to use the new path for brew though?

Look for a line like this:

eval "$(/usr/local/bin/brew shellenv)"

and change it to invoke brew via the AS path:

eval "$(/opt/homebrew/bin/brew shellenv)"

[SaschaKo77]

Thanks for your kind words. In my .zshrc I added
export PATH=/opt/homebrew/bin:$PATH

[dvessel]

To check all the executables from homebrew:
for f in $(brew list); do echo $f && for e in $(brew unlink --dry-run $f | pcregrep -o1 "$(brew --prefix)/bin/(.*)"); do file `which $e`; done; done

[gromgit]

A faster alternative that only uses standard system tools (and brew):

find $(brew --cellar) -path '*/*bin/*' -type f -exec file {} + | grep Mach-O

[nodesocket]

I've successfully migrated all my brew packages into /opt/homebrew and I'm ready to uninstall everything in the old /usr/local/.... What's the best practice way of uninstalling and removing all those packages?

The Homebrew uninstall script will uninstall everything I want to keep in /opt/homebrew:

https://raw.githubusercontent.com/Homebrew/install/HEAD/uninstall.sh

[carlocab]

Run the uninstall script under Rosetta.

[cho-m]

Another option is to use the uninstaller's --path=/usr/local argument, which should override searching the default prefixes.

In case you use Rosetta, make sure either /usr/local/bin/brew is before /opt/homebrew/bin/brew on PATH, or remove both from PATH since the uninstall.sh currently checks brew --prefix before the arch-default dir

[alexreg]

Is there a recommended way to transfer over things installed by Homebrew formulas in /usr/local? For example (but not limited to), Python's or Node's packages. I realise that packages with native extensions may need recompilation, but this would be a good start at least.

[SMillerDev]

maybe npm ls --global --parseable --json will work?

[alexreg]

Thanks for the advice, all. I'll give that a go.

[alexreg]

@SMillerDev How do I then install that list of packages?

[gromgit]

Not a Node user, but a quick bit of experimentation suggests the following for global modules:

/bin/ls /usr/local/lib/node_modules/ | while read m; do
  /opt/homebrew/bin/npm install --global "$m"
done

[alexreg]

@gromgit Thanks!

[tiptongrange]

After using brew bundle dump, is there any reason to not remove the Intel version first, before installing the M1 version, to remove any ambiguity of what's being removed?

[gromgit]

You could do that, or you could just tell the uninstaller which HOMEBREW_PREFIX to use, after you're sure the M1 version works for you:

curl -fsSL -o /tmp/uninstall.sh https://raw.githubusercontent.com/Homebrew/install/HEAD/uninstall.sh
/bin/bash /tmp/uninstall.sh --path=/usr/local

[gbelanger]

Thanks everyone for the tips. I went through and put this together for myself and my son to not spend the hour and a quarter doing this also.

## Migrating Homebrew from Intel to M1

## You can copy and paste into the Terminal

## Go to home directory
cd ;

## Create list of installed Intel packages
brew bundle dump ;

## Install new version of Homebrew
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)" ;

## Update the PATH to point to M1 version first
eval "$(/opt/homebrew/bin/brew shellenv)" ;
echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zshrc ;

## Migrate Intel packages (/usr/local/bin/brew) to M1 (/opt/Homebrew)
## You may need to enter your sysadmin password
brew bundle --file Brewfile ;

## Update packages
brew update ; 

## Upgrade packages
brew upgrade ;

## Clean up
brew cleanup ;

## Uninstall old Intel version

# Download uninstall script
curl -fsSL -o ./uninstall.sh https://raw.githubusercontent.com/Homebrew/install/HEAD/uninstall.sh ;

# Run the uninstall specifying the old path
sudo /bin/bash ./uninstall.sh --path=/usr/local ;
# Enter password
# Type Y to uninstall

# Delete uninstall script
rm uninstall.sh ;

# Final cleanup
brew cleanup ;

[gromgit]

Well, the OP did migrate the cask-installed apps to their new machine, hence the "already installed" errors from brew bundle. Assuming the migrated apps are universal, does copying the Caskroom directory over suffice?

[philippstorl]

Thanks. This helped me after some research.

[malikbenkirane]

It worked perfectly. I was struggling with podman formulae, and I'm done with it. Thank you so much!

[Gnosnay]

Thank you sooooooooooooooooo much!!! it helps a lot!

[dnszero]

I had the same problem and this worked great for me.

Thanks again for documenting this!

[jchunkins]

I had the homebrew version of bash installed on my old mac, and did a Time Machine restore of a backup onto my new Apple Silicon mac. The new mac is running Mac OS Monterey. The version of bash I was using is not a universal binary, and only contains the x86_64 executable:

$ lipo -info /usr/local/bin/bash
Non-fat file: /usr/local/bin/bash is architecture: x86_64

I've been using iTerm for my terminal, and despite the fact that I don't have iTerm set to Open using Rosetta, I would get the following from uname because of the version of bash I have set:

$ $SHELL --version
GNU bash, version 5.0.0(1)-release (x86_64-apple-darwin16.7.0)
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ uname -m
x86_64

$ uname -p
i386

Again, even if I were to use Apple's version of bash from /bin/bash the result would be the same:

$ /bin/bash -c "uname -p"
i386

$ /bin/bash -c "uname -m"
x86_64

So as-is, if I were to attempt an install of homebrew I'd be installing the x86_64 version of homebrew, and not the Apple Silicon version.

So to ensure that the install would really give me the Apple Silicon version, I used the arch -arm64 command to force Apple's version of bash (which is a universal binary) to run as arm64 architecture:

## prove that Apple's version of bash is really a universal binary
$ lipo -info /bin/bash
Architectures in the fat file: /bin/bash are: x86_64 arm64e

## prove that the arch -arm64 will really run as Apple Silicon
$ arch -arm64 uname -m
arm64

$ arch -arm64 uname -p
arm

$ arch -arm64 /bin/bash -c "uname -m"
arm64

$ arch -arm64 /bin/bash -c "uname -p"
arm

## perform the actual install
$ arch -arm64 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Hope this helps.

[edwardchoijc]

I had the same problem as you, but I solved this with the following. Then you don't have to prefix every cmd with arch -arm64

ζ uname -m
x86_64

# Run your shell with the specific arch
ζ env /usr/bin/arch -arm64 /bin/zsh --login

ζ uname -m
arm64

What's more, you can switch back to Intel with param '-x86_64'

[Kryan90]

I was concerned I had just went through the whole process only to actually be reinstalling with x86_64 since my uname -m also returned x86_64, but checking with

brew config
...
HOMEBREW_PREFIX: /opt/homebrew
CPU: 10-core 64-bit arm_firestorm_icestorm
Rosetta 2: false

Seems to indicate it did still install the arm64 version

[jchunkins]

Once everything was installed, for me the easiest route was to set my bash profile to use these aliases:

alias ibrew='arch -x86_64 /usr/local/bin/brew'
alias mbrew='arch -arm64e /opt/homebrew/bin/brew'

One thing I did notice recently was the option for -arm64e instead of just -arm64, in the arch man page, so I used that since it calls out Apple Silicon explicitly. Not sure there's any difference between the two though.

At any rate, you can see the interesting differences between the two configurations:

$ diff /tmp/a/ibrew.txt /tmp/a/mbrew.txt
1,7c1,7
< $ ibrew config
< HOMEBREW_VERSION: 3.4.11
< HOMEBREW_PREFIX: /usr/local
< Homebrew Ruby: 2.6.8 => /usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/2.6.8/bin/ruby
< CPU: 10-core 64-bit westmere
< macOS: 12.4-x86_64
< Rosetta 2: true
---
> $ mbrew config
> HOMEBREW_VERSION: 3.4.10
> HOMEBREW_PREFIX: /opt/homebrew
> Homebrew Ruby: 2.6.8 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
> CPU: 10-core 64-bit arm_firestorm_icestorm
> macOS: 12.4-arm64
> Rosetta 2: false