1. Creating bootable USB Installer can be done in different ways specifically create bootable USB Installer for macOS X El Capitan on Windows and other macOS versions. The first way to do manually and the second way is to do a software that is pre-build to do all those with a click or two.
2. Use Terminal to Create the El Capitan Bootable USB Installer. Follow these steps to create a bootable USB installer of El Capitan in Terminal. Connect the USB flash drive to your Mac. Give the flash drive an appropriate name. You can do this by double-clicking the device's name on the desktop and then typing a new name.

How To Make A Bootable Usb Drive

MacOS Sierra; OS X El Capitan; Create bootable USB drive with Mac Disk Utility. Now that you have the installation files ready on your Mac, you can move them to your USB drive for future use. To install macOS on an external hard drive: 1. Connect the USB to your MacBook. Open Disk Utility by following Applications → Utilities → Disk. Step 5: Once the progress bar is at 100%, a bootable macOS USB is ready. After that, you can use that USB drive for installing macOS. This is one of the easiest way to create a bootable macOS USB on a Windows PC. The steps are simple and instructions are pretty clear.

*Quick note from Save Apple Dollars - Older OS X Images can now be downloaded directly from Apple at https://support.apple.com/en-us/HT211683 please right click on the image link and select “save as”.

By Roman Loyola at www.macworld.com

Senior Editor, Macworld | JUL 3, 2017 1:32 PM PDT

Apple uses its App Store to distribute its software, like new Mac operating systems. It’s convenient, but sometimes it can take a while for a download to finish. And if you have multiple Macs, it’s inefficient to download the new OS to each and every Mac.

That’s why I like to make a bootable external drive for the sole purpose of installing the Mac operating system. When I need to tend to a bunch of Macs, it’s much faster to use a bootable drive instead of going to each Mac, launching the App Store, searching for the operating system, downloading it (after entering my Apple ID), and then running the installer.

You can create a bootable USB flash drive with the macOS Sierra installer that’s now available. The installer software will take up nearly 5GB of storage space. Here’s how to create a bootable macOS Sierra installer drive.

Macworld also has bootable-install-drive instructions for:

Lion (OS X 10.7)

Download the macOS Sierra installer

Launch the App Store app, then look for macOS Sierra in the store. (Here’s a link.) Click on the Download button, and your Mac will download the installer to your Applications folder. If it automatically launches after download, quit the installer.

Keep the installer in the Applications folder.

If you’ve already upgraded your Mac to Sierra, the installer is removed from the Applications folder. You can download it again if you go to Purchased in the App Store. Look for macOS Sierra in the list of apps that you’ve bought, and click on the Download button. If it automatically launches after download, quit the installer.

Get an external drive

You can use a USB flash drive or a hard drive with room for the installer software. I’ve used different drives with success, including a VisionTek 120GB USB 3.0 Pocket Solid State Drive ($83 on Amazon) and an old 8GB Iomega Micro Mini Hard Drive.

Don’t worry if the drive isn’t formatted for the Mac. The drive will be reformatted automatically as part of the process. Change the name of your drive to Untitled; you need to do this for the steps below.

The quick and easy way

The process detailed below involves the Terminal. If your really don’t want to use Terminal, there are a couple of free apps you can use.

• Install Disk Creator is a straightforward way to create a boot disk. I was able to make a macOS Sierra external USB boot disk in a few minutes, and the installation worked without a hitch. Also works with older versions of OS X.

• Diskmaker X is a popular app. It also supports older versions of OS X.

Use the Terminal to create a boot disk

So you have your external drive, and the Sierra beta installer is in place. Now you’re going to use Terminal to create a boot drive. If you’ve never used Terminal before, don’t worry. This is pretty easy.

Here are the steps to create a macOS Sierra beta boot disk. (Apple also has these instructions.)

1. Connect the external drive to your Mac. (In the Terminal command you will use, I use Untitled to represent your external drive. If your drive is named something else, you need to change Untitled to the name of your drive.)

2. Launch Terminal (/Applications/Utilities/Terminal.app).

3. Copy the following:
   sudo /Applications/Install macOS Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install macOS Sierra.app

4. Go back to Terminal and paste the copied code at the prompt.

5. Terminal will ask for a password. This is your user password. Terminal doesn’t display characters when you type it in. Hit Return.

6. Terminal will tell you that it will erase your drive. To confirm that you want to continue, type Y and hit Return.

7. You’ll see that Terminal erases your drive. When that part is done, your Mac may ask you if you want to use the drive for Time Machine. Click Don’t Use.

8. Terminal will copy the installer file to your drive. This will take a few minutes.

9. After copying, Terminal is done. You should see Terminal display a “Copy complete” and Done notice. You can quit Terminal and your drive is ready for use.

How to boot from the installer drive

1. Plug your external drive into your Mac.

2. Power up (or restart) your Mac. Press down on the Option key while the Mac boots.

3. After a few moments, your Mac should display the Startup Manager, which will show you the available boot drives. Click on the external drive and hit Return. (You don’t need to select a network to proceed.)

4. Your Mac will display an OS X Utilites window. If you want to install Sierra and leave the data intact, select Install OS X. If you want to start over and wipe out the data, you need to go into Disk Utility to reformat the internal drive first, and then install macOS Sierra.

Full Credit for this article is given to Roman Loyola and www.macworld.com please visit their website for more helpful information about fixing Macs.

Customers get Software upgrades for Mac computers through the online app store ever since the release of macOS Lion. Be it a clean install or upgrade, Mac App store require you connect to the internet to download whole installation files. The online OS update is OK if you have stable broadband connectivity and enough bandwidth. Apple also provides an option for internet recovery of macOS if your computer fails to boot. But there are situations where you can’t download the OS from the Apple servers. Having a macOS offline installer or a bootable USB disk is the only solution in such scenarios.

Download macOS offline Installer

Installing macOS without internet requires a bootable USB disk. And you need to download a full-size macOS installer for making this disk. Hence, before anything, we will tell you how to download macOS offline installer directly from Apple to your Mac using a GitHub script.

Download the gibMacOS script from this link and extract it to your Mac. From the extracted folder, run the script called gibMacOS.command — it will open the Terminal as shown below.

Create Macos El Capitan Bootable Usb

Wait for the script to fetch the macOS download catalogue from Apple. When the list is ready choose a number as per your OS option and press the Return/Enter key. You can use this script to download macOS Big Sur (11.1), Catalina (10.15), Mojave (10.14), and High Sierra (10.13.6). A new folder “macOS downloads” appears in the “gibMacOS-master” as you provide a download option, and the OS starts downloading as you can see in the video.

The OS gets downloaded as parts, PKGs, DMGs and other files. For macOS versions up-to Big Sur, you need to use another script “BuildmacOSInstallApp.command” in the main folder to join all the downloads and make the full macOS installer app. All you need is to drag and drop the downloaded macOS folder to the terminal window. The script will build the offline installer and save it to the same folder.

You don’t need to use the second script if your choice is macOS Big Sur. Because, for macOS Big Sur you get a full-size installer from Apple in PKG format. Double-click and open the InstallAssistant.PKG to save the “Install macOS Big Sur.app” to the Applications folder.

Apart from this, some older versions of macOS are available for direct download from Apple (Sierra, EL Capitan, Yosemite) in DMG format.

How to make a macOS bootable USB installer

It is possible to create a backup macOS installer on a DVD or USB drive but later is the best choice. Most of the Macs these days don’t have DVD slots, and the installation through a disc is very slow. Hence we discuss only about making macOS recovery installer on a USB disc. For this you need a Mac and a USB pen drive of at least 8 GB space, and a third-party app called DiskMaker.

1. First, download a copy of Disk Maker from the official website.
2. Choose a version as per your requirement. For example, if you want make USB installer for macOS Catalina 10.15, download Disk Maker X 9.
3. I use an MacBook Pro with High Sierra. Hence, I’m downloading disk maker X 7.
4. The next step is to download full macOS installer from the App Store to your Applications folder.
5. Run Disk Maker DMG installer and copy the app to the Applications.
6. The application will automatically detect the downloaded macOS as shown in the screenshot. Select “Use this Copy” if you would like to proceed with it.
7. Next is setting the USB pen drive for creating the bootable installer. Choose the third option ” An 8 GB USB Thumb drive.”
8. The app will list all drives in your system. Pick the one you would like use as macOS USB installer.
9. Ignore the warning message and proceed to Erase and Create macOS USB disk. Don’t forget to provide your admin password when it prompts.
10. Keep checking notifications tab for progress. When it completes you will find Install macOS Mojave (or High Sierra) mounted to your desktop as a USB disk.
11. That’s your backup. Unmount and keep the USB installer to a safe place.

How To Create A Bootable Macos El Capitan Usb Install Drive

Unfortunately, the above app is not compatible with macOS Big Sur 11 and above. Check the instructions on Apple website, the manual method to make macOS offline USB installer.

What is the alternative if I don’t have usable Mac at the moment?

This method is applicable when you have a Mac, and the internet recovery fails. But think about a situation when your only Mac stops to boot, and you don’t have USB installer or TimeMachine backup! Downloading MacOS DMG file might save you. If you have a macOS DMG, you can create bootable USB disk from a Windows PC — use a software like TransMac for this purpose.

Make Os X El Capitan Boot Usb

Clean installing or restoring a Mac offline with USB pen drive

As said earlier, you could use the macOS USB installer to do a clean install or restore it upon a boot failure. Just connect the USB disk and press the Option/Alt Key when you hear the boot sound. The Mac will then display all the startup disks available.

Pick the USB drive starting with the label “Install macOS” and follow on-screen instructions to complete the installation. If you need, use the Disk Utility to format the drive for doing a clean install.