- It can also help in situations where the operating system is corrupted or installation from app store shows errors. To create a bootable macOS installation disk, you have to burn the DMG file to a USB drive as CD/DVD is not available for Mac computers. Here's how to do it from text commands and using a purpose-built software called WizDMG.
- There are two ways to run the version of macOS from your external drive. Either: Open System Preferences Startup Disk. Select the external drive you wish to use to start up the Mac and click.
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Step 8: Erase & Create the New Disk. https://yellowprofessor993.weebly.com/blog/download-torrent-on-xbox-one. At the warning, select 'Erase then create the disk.' Then hit 'Continue.' In a minute or so, it'll ask you for your admin password. Input it, then be prepared to wait awhile, depending on the speed of your USB drive.
If you are planning to install macOS Catalina, there is one additional set of steps you should follow. You should download a bootable copy of macOS Mojave. This is the only way to downgrade if you decide you're not ready for macOS Catalina.
Before you start
Before you get started, make sure you have a thumb drive with at least 15GB of storage, or a spare external hard drive (one that you don't use with anything else).
You'll also need to download macOS Mojave from the Mac App Store.
Note: After macOS Mojave has downloaded, it will automatically begin the installation process. Close the installer instead.
Please, Please, Please, backup your Mac before you do anything.
How to format your external drive for Mac
You'll need to start with a clean thumb drive or hard drive in order to get it ready to work as a bootable drive.
- Plug the USB end of the drive to a USB port on your Mac.
- Click on Finder in your Dock to open a Finder window.
- Select Applications from the list on the left side of the window.
- Scroll down and double-click on Utilities.
- Scroll down and double-click on Disk Utility.
- Select your drive under External.
- Click on the Erase tab at the top of the window.
- Note the name of your external hard drive (probably 'Untitled') because you will need it when you create a bootable drive. If you have more than one external hard drive named 'Untitled,' you will need to rename your hard drive now.
- If your Mac is using HFS+, select Mac OS Extended (Journaled) from the format list. If your Mac is using APFS, select APFS from the format list.
- If Scheme is available, select GUID Partition Map.
- Click Erase.
- Click Done when the process is complete.
- Close the Disk Utility window.
Your thumb drive or external hard drive is now ready.
How to make your external drive bootable for installing macOS Mojave
Important:You will need to be in your Mac's administrator account in order to run the sudo Terminal command. Open dmg on windows. Whats a dmg file on mac.
- Click on Finder in your Dock to open a Finder window.
- Select Applications Free download stopwatch for mac. from the list on the left side of the window.
- Scroll down and double-click on Utilities.
- Scroll down and double click on Terminal.
- Recall the name of your formatted external drivewhen entering the following text into Terminal. If it is not named 'Untitled,' you will need to change the command syntax for the pathname where it says: Volumes/Untitled. The name of the drive can't have any spaces and it is case sensitive.
- Poe chaos dmg. Enter the following text into Terminal (Don't forget to change the name 'Untitled' if your hard drive is named something else):sudo /Applications/Install macOS Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled
- How do i mount a dmg file on a mac. Hit the enter/return key.
- Enter your administrator account password. This is the password you use to make changes on your Mac or log in. No text will appear in Terminal when you enter the password.
- Type Y to confirm that you want to erase the drive and press return.
The process could take a very long time, depending on the drive. When it is done, the Terminal window will report 'Done.'
How to use macOS Mojave as an installer boot drive
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Once macOS Mojave is installed on your external drive, you can boot up and install any Mac with the drive plugged into it.
- Turn off the Mac you want to install macOS Mojave with the bootable drive.
- Connect the external drive to your Mac via the USB port.
- Turn on your Mac.
- Hold down the Option key when you hear the startup chime.
- Select the external drive with macOS Mojave on it from the list of systems to start up your computer.
The installation process will begin. Follow the steps to install macOS Mojave onto your Mac or partitioned hard drive.
Do you have any questions about how to create a bootable installer drive for macOS Mojave? Let us know in the comments.
Updated September 2019: Updated for macOS Catalina.
macOS Catalina
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Tips
By William Gallagher
Tuesday, September 25, 2018, 10:59 am PT (01:59 pm ET)
Apple makes installing macOS very simple —if you only have one Mac. When you have many, it takes an unnecessarily protracted time. Circumvent Apple's installer and create your own using the Terminal.Tuesday, September 25, 2018, 10:59 am PT (01:59 pm ET)
We shouldn't complain. To install macOS Mojave on your Mac, you just download it and let Apple's installer do its job. Only, that installer is big —circa 6GB —so downloading it can take a time. And once it's run, Apple immediately deletes it. To install Mojave on a second or third or fourth Mac, you're supposed to re-download it to each one.
Given that we have lives as well as multiple Macs, we need to do something about this. Rather than working through Apple's installer, you download that once and stop it before it begins working. Then type some commands in Terminal to extract Mojave, and put the installer on an external drive so you can re-use it without having to download it every time.
This is one of the easiest uses of the Terminal program on Macs —but it still needs you to take care —and in this case to specifically copy and paste the instructions into it. A stray typo isn't likely to cause you problems, it's more likely to just not work, but it can.
Then, too, this is ultimately about installing a major macOS update onto all your Macs so that thought you had a moment ago about backups is spot on. Make a backup. Make two.
What you need
Get Apple's macOS Mojave installer and start downloading it. Most of us will get it from the Mac App Store but if you have a developer account, you can elect to get the latest beta from developer.apple.com instead.
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While that download is happening, pick a drive —USB or Thunderbolt-connected —that you can use as a Mojave install disk. It will end up erased and with only the Mojave installer on it so really pick one you can spare.
If that's an SSD one then you'll be glad: the speed of the installation depends hugely on how fast your drive is.
Prepare the drive
Mount the drive or the volume that you want to do this on. That drive can be called anything you like but so that you can just copy and paste our Terminal instructions, rename it macinstall. You can rename it again later.
When Apple's macOS Mojave installation app is downloaded, launch it but don't let it start the installation process. Click on the Install macOS Mojave menu and choose Quit Install macOS.
Make a copy of Apple's installer. It'll be in your Applications folder with the name Install macOS Mojave. Copy it to another folder or drive just so that you know you never have to schlep through this downloading again —at least until next year.
Terminal velocity
With Apple's installer safely copied somewhere and the drive you want to make into a bootable installer ready and mounted, now you open Terminal.
It's in Applications, Utilities. It opens to a command line: copy and paste the following into it:
sudo /Applications/Install macOS Mojave.app/Contents/Resources/createinstallmedia—volume /Volumes/macinstall
Hit return and you'll be asked for your Mac admin password. When you enter that, Terminal starts running a program called createinstallmedia. It's an Apple program: they've created it for us all, they just haven't mentioned it much.
Terminal and createinstallmedia will remind you that this means erasing the drive and if you enter Y then it will start the process. First it erases the drive and you'll see it report '10% 20%' as it goes.
Then when that's done, it automatically copies the installer files —the Install macOS Mojave downloader from Apple —onto the drive. Lastly it makes that drive bootable.
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How To Create A .dmg Of A Mac Drive And Store It On An External Drive Windows 10
What you end up with
Depending on the speed and age of both your Mac and your hard drives —both the spare and the one you're currently booted from —this could take anywhere up to 20 minutes.
After that, type exit into Terminal and when it says Process Completed then choose File, Quit.
Now you have a drive called macinstall. It's bootable and it contains only the macOS Mojave installer. That means you can eject that drive and take it to any or all Macs you've got. Plug it into each one in turn, reboot the Mac from it and run the Mojave installer.
The process will still take some time —but an external installer will save you the substantially long and tedious time it would take downloading the installer for macOS onto each Mac from Apple's servers.
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