Migrating a MacPorts installation

A MacPorts installation is designed to work with a particular operating system and a particular hardware architecture. Problems may occur after major system changes, such as:

• major operating system upgrades (e.g., from 10.9 Mavericks to 10.10 Yosemite).
• architecture migrations (e.g., from PowerPC to Intel).
• migrations from one computer to another

Please follow this procedure to ensure a smooth transition. (This isn't necessary if you only upgrade Xcode.)

Note: If you move from on Mac to another mac using ​Migration Assistant, you have to do it first.

Migration procedure

1. Install the latest version of Xcode and the Xcode command line tools

After a major system change, update the development tools by ​installing the latest version of Xcode. Open the Xcode application once after installation and follow any prompts. Install the command line tools package as well (run xcode-select --install).

2. Reinstall MacPorts base system

To reinstall, simply install the base MacPorts system for your new platform.

Update macports.conf: If your macports.conf (typically at /opt/local/etc/macports/macports.conf) contains uncommented settings for universal_archs or build_arch, you will likely want to update them, since unlike earlier OS versions, the compiler on Snow Leopard and later will build for x86_64 by default on systems that support it. The default values will be fine for almost all users, so unless you know you need something different, just comment out these two lines. Several other settings in macports.conf have changed their defaults over the years. Take a moment to compare each line of your macports.conf with the corresponding line in macports.conf.default in the same directory. Unless you know a reason why a line in your settings file should be different from the defaults, adopt the line from the defaults file.

3. Reinstall your ports
   1. Save the list of installed ports:

      port -qv installed > myports.txt
      

   2. (optional) Save the list of requested ports:

      port echo requested | cut -d ' ' -f 1 > requested.txt
      

   3. Uninstall all installed ports:

      sudo port -f uninstall installed
      

   4. Clean any partially-completed builds:

      sudo rm -rf /opt/local/var/macports/build/*
      

   5. Download and execute the restore_ports script. (If you installed MacPorts from source and used a custom prefix, then you'll need to use the -p option when you run restore_ports.tcl; see ./restore_ports.tcl -h.)

      curl --location --remote-name https://github.com/macports/macports-contrib/raw/master/restore_ports/restore_ports.tcl
      chmod +x restore_ports.tcl
      sudo ./restore_ports.tcl myports.txt
      

      Note: ports that are not available on your new platform will be skipped without error.
   6. (optional) Restore requested status: If you saved the list of requested ports, you can now restore the requested flags for your newly installed ports to their former states.

      sudo port unsetrequested installed
      xargs sudo port setrequested < requested.txt
      

      Warning: if a port in requested.txt was not installed in the previous step, the iterative setrequested will terminate, leaving some ports still marked as not-requested. Edit requested.txt to remove any ports that were not installed and repeat this step. Double check your desired ports are set as requested with port echo requested.

Troubleshooting

Though it is now quite well-tested, the restore_ports script may fail in some cases. One known issue is that the script will fail if there are conflicting ports in the list. It's possible to have conflicting ports installed provided at most one of the conflicting set is active. If the script fails for this reason, you can delete one of the conflicting ports from myports.txt and then simply run the script again. You may need to do this multiple times if there are multiple conflicting ports listed.

In the worst case, you can reinstall your ports manually by browsing myports.txt and installing the ports one by one, remembering to specify the appropriate variants:

sudo port install portname +variant1 +variant2 …

Note that if you have specified variants which are not the default, you may need to install ports in an order other than the alphabetical order recorded in myports.txt. You may skip explicitly installing ports that you did not request as long as they are not using non-default variants, since they will be installed as dependencies of other ports.

If things go really wrong, don't forget that you can always ​uninstall MacPorts entirely before manually reinstalling ports.

Another potential problem is that the restore_ports.tcl command may fail with a Too many open files error message. Under macOS Sierra, the default shell has a default ulimit of 256 open files. The solution is to restore the ports with a slightly modified command:

sudo bash -c "ulimit -n 4096; ./restore_ports.tcl myports.txt"

This will raise the file limit for the duration of the restore_ports.tcl command.