1. Macを仮想化したい等でmacOSのインストールイメージ(ISOファイル)を作成したいことがあります。コマンドである程度自動的に作成する方法と手動で作成する方法の2つを紹介します。 目次 1 macOSのダウンロード(Catlina)2 I.
2. MacOS / OSXのUSB起動ディスクを作る 古いMacを購入した際にOSをインストールするときや、macのOSを再インストールしたいとき、古いmacOS / OSXのインストーラーが必要となる場合がある。ここでは、USBや.

So, you’ve decided to download an older version of Mac OS X. There are many reasons that could point you to this radical decision. To begin with, some of your apps may not be working properly (or simply crash) on newer operating systems. Also, you may have noticed your Mac’s performance went down right after the last update. Finally, if you want to run a parallel copy of Mac OS X on a virtual machine, you too will need a working installation file of an older Mac OS X. Further down we’ll explain where to get one and what problems you may face down the road.

How to downgrade a Mac running later macOS versions. If your Mac runs macOS Sierra 10.12 or macOS High Sierra 10.13, it is possible to revert it to the previous system if you are not satisfied with the experience. You can do it either with Time Machine or by creating a bootable USB or external drive. Instruction to downgrade from macOS Sierra. MacOS and BootCamp Latest. GitHub Gist: instantly share code, notes, and snippets.

A list of all Mac OS X versions

We’ll be repeatedly referring to these Apple OS versions below, so it’s good to know the basic macOS timeline.

STEP 1. Prepare your Mac for installation

Given your Mac isn’t new and is filled with data, you will probably need enough free space on your Mac. This includes not just space for the OS itself but also space for other applications and your user data. One more argument is that the free space on your disk translates into virtual memory so your apps have “fuel” to operate on. The chart below tells you how much free space is needed.

Note, that it is recommended that you install OS on a clean drive. Next, you will need enough disk space available, for example, to create Recovery Partition. Here are some ideas to free up space on your drive:

• Uninstall large unused apps
• Empty Trash Bin and Downloads
• Locate the biggest files on your computer:

Go to Finder > All My Files > Arrange by size
Then you can move your space hoggers onto an external drive or a cloud storage.
If you aren’t comfortable with cleaning the Mac manually, there are some nice automatic “room cleaners”. Our favorite is CleanMyMac as it’s most simple to use of all. It deletes system junk, old broken apps, and the rest of hidden junk on your drive.

Download CleanMyMac for OS 10.4 - 10.8 (free version)

Download CleanMyMac for OS 10.9 (free version)

Download CleanMyMac for OS 10.10 - 10.14 (free version)

STEP 2. Get a copy of Mac OS X download

Normally, it is assumed that updating OS is a one-way road. That’s why going back to a past Apple OS version is problematic. The main challenge is to download the OS installation file itself, because your Mac may already be running a newer version. If you succeed in downloading the OS installation, your next step is to create a bootable USB or DVD and then reinstall the OS on your computer.

How to download older Mac OS X versions via the App Store

If you once had purchased an old version of Mac OS X from the App Store, open it and go to the Purchased tab. There you’ll find all the installers you can download. However, it doesn’t always work that way. The purchased section lists only those operating systems that you had downloaded in the past. But here is the path to check it:

1. Click the App Store icon.
2. Click Purchases in the top menu.
3. Scroll down to find the preferred OS X version.
4. Click Download.

This method allows you to download Mavericks and Yosemite by logging with your Apple ID — only if you previously downloaded them from the Mac App Store.

Without App Store: Download Mac OS version as Apple Developer

If you are signed with an Apple Developer account, you can get access to products that are no longer listed on the App Store. If you desperately need a lower OS X version build, consider creating a new Developer account among other options. The membership cost is $99/year and provides a bunch of perks unavailable to ordinary users.

Nevertheless, keep in mind that if you visit developer.apple.com/downloads, you can only find 10.3-10.6 OS X operating systems there. Newer versions are not available because starting Mac OS X Snow Leopard 10.7, the App Store has become the only source of updating Apple OS versions.

Purchase an older version of Mac operating system

You can purchase a boxed or email version of past Mac OS X directly from Apple. Both will cost you around $20. For the reason of being rather antiquated, Snow Leopard and earlier Apple versions can only be installed from DVD.

Buy a boxed edition of Snow Leopard 10.6
Get an email copy of Lion 10.7
Get an email copy of Mountain Lion 10.8

The email edition comes with a special download code you can use for the Mac App Store. Note, that to install the Lion or Mountain Lion, your Mac needs to be running Snow Leopard so you can install the newer OS on top of it.

How to get macOS El Capitan download

If you are wondering if you can run El Capitan on an older Mac, rejoice as it’s possible too. But before your Mac can run El Capitan it has to be updated to OS X 10.6.8. So, here are main steps you should take:

1. Install Snow Leopard from install DVD.
2. Update to 10.6.8 using Software Update.
3. Download El Capitan here.

“I can’t download an old version of Mac OS X”

If you have a newer Mac, there is no physical option to install Mac OS versions older than your current Mac model. For instance, if your MacBook was released in 2014, don’t expect it to run any OS released prior of that time, because older Apple OS versions simply do not include hardware drivers for your Mac.

But as it often happens, workarounds are possible. There is still a chance to download the installation file if you have an access to a Mac (or virtual machine) running that operating system. For example, to get an installer for Lion, you may ask a friend who has Lion-operated Mac or, once again, set up a virtual machine running Lion. Then you will need to prepare an external drive to download the installation file using OS X Utilities.

After you’ve completed the download, the installer should launch automatically, but you can click Cancel and copy the file you need. Below is the detailed instruction how to do it.

STEP 3. Install older OS X onto an external drive

The following method allows you to download Mac OS X Lion, Mountain Lion, and Mavericks.

1. Start your Mac holding down Command + R.
2. Prepare a clean external drive (at least 10 GB of storage).
3. Within OS X Utilities, choose Reinstall OS X.
4. Select external drive as a source.
5. Enter your Apple ID.

Now the OS should start downloading automatically onto the external drive. After the download is complete, your Mac will prompt you to do a restart, but at this point, you should completely shut it down. Now that the installation file is “captured” onto your external drive, you can reinstall the OS, this time running the file on your Mac.

1. Boot your Mac from your standard drive.
2. Connect the external drive.
3. Go to external drive > OS X Install Data.

Locate InstallESD.dmg disk image file — this is the file you need to reinstall Lion OS X. The same steps are valid for Mountain Lion and Mavericks.

How to downgrade a Mac running later macOS versions

If your Mac runs macOS Sierra 10.12 or macOS High Sierra 10.13, it is possible to revert it to the previous system if you are not satisfied with the experience. You can do it either with Time Machine or by creating a bootable USB or external drive.
Instruction to downgrade from macOS Sierra

Instruction to downgrade from macOS High Sierra

Instruction to downgrade from macOS Mojave

Instruction to downgrade from macOS Catalina

Before you do it, the best advice is to back your Mac up so your most important files stay intact. In addition to that, it makes sense to clean up your Mac from old system junk files and application leftovers. The easiest way to do it is to run CleanMyMac X on your machine (download it for free here).

Visit your local Apple Store to download older OS X version

If none of the options to get older OS X worked, pay a visit to nearest local Apple Store. They should have image installations going back to OS Leopard and earlier. You can also ask their assistance to create a bootable USB drive with the installation file. So here you are. We hope this article has helped you to download an old version of Mac OS X. Below are a few more links you may find interesting.

古いMacを購入した際にOSをインストールするときや、macのOSを再インストールしたいとき、古いmacOS / OSXのインストーラーが必要となる場合がある。ここでは、USBやSDカードにmacOSのインストーラーを書き込み、起動可能なディスクにする方法を記載していく。

起動ディスクを作るにあたっていくつか必要なものが存在する。
●*macOSのインストーラー
●8GB以上のUSBやSDカードなど
●もう1台のMac

*macOSのインストーラーは現在、AppStoreからは最新のOSしかダウンロードすることはできない。つまり、OSXのインストーラーが必要な場合にはインターネットリカバリーを行うもしくはOSXのインストールディスクをAppleStoreから購入する必要がある。

古いmacOSのインストーラーを持っていない場合や、AppStoreから入手できない場合はこちらの記事を参照

まずは、macOSのインストーラーをアプリケーションフォルダ内に入れておく。
次にインストールするメディアに「ディスクユーティリティ」を使い、*「MyVolume」という名前をつける。
フォーマットは「Mac OS拡張（ジャーナリング）」を選択し、消去する。

*「MyVolume」は書込み作業を行う際の一時的な名前であるが、もし「MyVolume」という名前を使いたくない場合は、下記インストールコマンドの/Volumes/MyVolumeのMyVolumeを設定したい名前へと変更すれば良い。

それでは作業を始めていく。この方法はOSX10.9 Mavericks以降のみで使える。OSX10.8 Mountain Lion以前のバージョンではこの方法が使えないので、後述する「Lion / Mountain Lionでの作成」の項を参照してほしい。

1. ターミナルを開く
2. USBを作成したいバージョンのコマンドを下記の一覧からコピーする
3. ターミナルにペースト
4. パスワードが要求されるのでパスワードを入力
5. Yと入力
6. 30分程度で書き込みが終わり、起動可能なインストーラーが完成する。

Mavericks (10.9)

Yosemite (10.10)

ElCapitan (10.11)

Sierra (10.12)

HighSierra (10.13)

Mojave (10.14)

Catalina (10.15)

Macos Catalina Installesddmg.pkg

Big Sur (11.0)

もしMacOS X LionもしくはMountainLionの起動ディスクを作成する場合は、上記のコマンドを使用して作成することができない。よって以下の方法に絞られてしまう。

・AppleStoreよりインストールDVDを¥2222で購入
・ディスクユーティリティを使用してOSインストーラーからUSBに復元
・DiskMakerを使用してインストールディスクを作成(*後述)

もしLionかMountainLionのインストーラーを持っているのであれば、ディスクユーティリティを起動し、インストーラーのパッケージ内に含まれるInstallESD.dmgをUSBに復元する。

もし上記2つの方法で起動ディスクを作成できなかった場合、「DiskMaker」というアプリケーションを使用したディスクの作成方法がある。
ただし、MacやUSBメモリー, バージョンの相性問題などによって確実にインストーラーの作成が成功するとは限らないため、この方法は最終手段として考えてほしい。

1. インストーラーをアプリケーションフォルダに入れておく。
2. DiskMakerをダウンロード
3. 手順に沿って作成作業を行う

Macos Mojave Installesd.dmg Download

1. インストールするMacを*Optionキーを押しながら起動。
2. 起動したら、メディアをMacに差し込む
3. 起動ディスクとして先程のメディアを選択
4. macOSユーティリティ or OSXユーティリティが起動
5. インストール作業を進める

Macos Installesd.dmg

*Windowsキーボードを使用しているのであればAltキーを押下

Macos Installed

2020/01/25 掲載
2020/08/23 MojaveおよびCatalinaのコマンドを修正
2020/08/24 インストーラーの準備方法について追記
2020/11/29 macOS Big Surのコマンドを追記
2020/12/29 一部修正
2021/2/22 一部修正