sdagley / erase-install

A script to automate Apple's eraseinstall method to reinstall macOS

erase-install

by Graham Pugh

WARNING. This is a self-destruct script. Do not try it out on your own device!

erase-install.sh is a script to erase a Mac directly from the system volume, utilising the eraseinstall option of startosinstall, which is built into macOS installer applications since version 10.13.4.

If run without any options, the script will not perform the erase. This means that the script can also be used to pre-cache the installer, or simply to make it available for the user.

So, if run without any options, the script will do the following:

1. Check if an installer is already present in the working directory of this script from a previous run.
2. If not, check if an existing macOS installer is present in the /Applications folder. If present, checks that it isn't older than the current installed version.
3. If no valid installer is found, a forked version of installinstallmacos.py is downloaded. This is used to download the current macOS installer that is valid for this device (determined by Board ID and Model Identifier). The installer is compressed and placed in a .dmg in the working directory.

For more information on the forked version of installinstallmacos.py, see grahampugh/macadmin-scripts

There are a number of options that can be specified to automate this script further:

1. --erase runs the startosinstall command with the --eraseinstall option to wipe the device.
2. --move moved the macOS installer to /Applications if it isn't already there.
3. --overwrite deletes any existing downloaded installer and re-downloads it.

Full list of Options:

• Run the script with no arguments to download the latest production installer. By default, this is stored in a DMG in the working directory of the installinstallmacos.py script. If an existing installer is found locally on the disk (either in the default location or in /Applications), and it is a valid installer (>10.13.4), it will not download it again.

  sudo bash erase-install.sh
  

• Run the script with argument --overwrite to remove any existing macOS installer found in /Applications and download the latest production installer. By default, this is stored in a DMG in the working directory of the installinstallmacos.py script.

  sudo bash erase-install.sh --overwrite
  

• Run the script with argument --samebuild to check for the installer which matches the current system macOS build (using sw_vers), rather than the latest production installer. This allows the reinstallation of a forked or beta version that is already installed on the system volume.

  sudo bash erase-install.sh --samebuild
  

• Run the script with argument --version=10.14 to check for the installer which matches the specified macOS version. This basically filters by version, and looks for the lowest build matching the version. Useful during Golden Master periods.

  sudo bash erase-install.sh --version=10.14
  

• Run the script with argument --build=XYZ123 to check for the installer which matches the specified build ID, rather than the latest production installer or the same build. Note that it will only work if the build is compatible with the device on which you are running the script.

  sudo bash erase-install.sh --build=XYZ123
  

• Run the script with argument --move move the downloaded installer to the /Applications folder. Note that this argument does not apply in conjunction with the --erase flag.

  sudo bash erase-install.sh --move
  

• Run with --erase argument to check and download the installer as required and then run it to wipe the drive

  sudo bash erase-install.sh --erase
  

All possible combinations:

sudo bash erase-install.sh
sudo bash erase-install.sh --erase
sudo bash erase-install.sh --move
sudo bash erase-install.sh --version=10.14
sudo bash erase-install.sh --version=10.14 --move
sudo bash erase-install.sh --version=10.14 --erase
sudo bash erase-install.sh --build=XYZ123
sudo bash erase-install.sh --build=XYZ123 --move
sudo bash erase-install.sh --build=XYZ123 --erase
sudo bash erase-install.sh --samebuild
sudo bash erase-install.sh --samebuild --move
sudo bash erase-install.sh --samebuild --erase
sudo bash erase-install.sh --overwrite
sudo bash erase-install.sh --overwrite --move
sudo bash erase-install.sh --overwrite --version=10.14 --move
sudo bash erase-install.sh --overwrite --build=XYZABC --move
sudo bash erase-install.sh --overwrite --samebuild --move
sudo bash erase-install.sh --overwrite --erase
sudo bash erase-install.sh --overwrite --version=10.14 --erase
sudo bash erase-install.sh --overwrite --build=XYZABC --erase
sudo bash erase-install.sh --overwrite --samebuild --erase
sudo bash erase-install.sh --help

Requirements for performing the eraseinstall:

• macOS 10.13.4+ is already installed on the device
• Device file system is APFS

Note that downloading the installer does not require 10.13.4 or APFS, it is just the starts install --eraseinstall command that requires it.

Setting up in Jamf Pro

To run this script in Jamf Pro, upload the script, and then create a policy to run it. In the script parameters of the Policy, add the desired options, including the --.

For example, to create a policy named Erase and Reinstall macOS which is scoped models of Mac that can run the latest standard build, set parameters as follows:

• Parameter 4: --erase

If you need a particular fork, create a policy scoped to the devices that require the forked build, and set parameters as follows:

• Parameter 4: --erase
• Parameter 5: --build=18A389

Using the erase-install.sh script to cache the installer for use with the install-macos.sh script

If you want to pre-cache the installer in /Applications for use by another policy, make a policy named Download macOS Installer and set parameters as follows:

• Parameter 4: --move
• Parameter 5: --overwrite

If you want to upgrade to macOS 10.14 while 10.13 installers are still available in the catalog, add this additional flag:

• Parameter 6: --version=10.14

Once the installer is in place in /Applications folder, you can use the install-macOS.sh script included here in a different policy to perform an in-place upgrade, without erasing the system.