Dual Boot Mac OS Catalina  Mojave!

Let me show you the Easy Way and the Geeky Way to Dual Boot your Mac with MacOS Catalina and MacOS Mojave.
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Setting up a Dual Boot Mac:
Create a New APFS Volume to Install MacOS Catalina 10.15:
- Non-Geeky Way: Create New APFS Volume in Disk Utility Application
- Geeky Way: Create New APFS Volume from the Mac Terminal Command LineCommand: diskutil apfs addVolume diskContainerIdentifyer APFS DiskName
Install MacOS Catalina 10.15 on the new APFS Volume:
- Non-Geeky Way: Double-Click Catalina10.15.app and select the new APFS Volume.
- Geeky Way: Reboot to Recovery Partition and Install from Mac Terminal Command Line
Command: startosinstall --volume /Volumes/DiskName --agreetolicense --installpackage /Path_To_Package
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[@califormoi]

Oh wow, Beast Mode. You are a Sensei, I think Ninja is an understatement. I might have a few questions for you later, but just wanted to drop a thank you ;)

[@AppleNinja]

Thank you Cali For Moi. Have an amazing week!

[@BrooxFam]

I'm a little late to the party here, but I just purchased a new iMac that came with Catalina installed. I'd like to partition my HD to be able to restart my iMac in Mojave, but I'm running into some issues. First off, I can't seem to find a downloadable installer for Mojave. When I download from the app store I get an error message telling me the application doesn't work with this OS. I have a few older applications that are not available in 64-bit and I need to be able to update some client files now and then. I don't really want to keep around my old iMac just for a few functions. I like your communication style - very easy to follow. I'm hoping you can help me out. Thanks!

[@AppleNinja]

Hey Jay I think I know the issue. The Mojave installer will not run from a booted Catalina volume. You might be able to run an osinstall command from the terminal in recovery partition to get it installed. Otherwise you need a Mojave or earlier drive (usb stick) to boot from to do it.

[@BrooxFam]

@@AppleNinja I actually found another You Tube video (kzbin.info/www/bejne/lWrEaqmMhLN1oNU) that walked me through the steps to create a startup disk through partitioning a small section of my hard drive and loading the Mojave install file onto it through Terminal. Then I restarted the iMac with the Mojave Installation disk I just created and installed Mojave. I then installed Mojave onto another partitioned section of my hard drive to create a separate start-up disk. It worked perfectly!! Thanks!

[@c-mb5027]

Thank you for your movie. I recived a lot informations to do the same. I have now question... I am sure you know Carbon Copy Cloner. Do you know a solution to clone both volumes (both bootable) to an extern SSD (of course APFS formated and bootable)? To have a "100%" backup? Thank you for your answer!

[@jamesfisher6515]

I have big sur on my MacBook and I want to dual boot with mountain lion how would I do it or is it the same way

[@jamzam9807]

What if I’m already on Big Sur, abs I want to make a new volume and out Mojave on to that volume, how do I downgrade to Mojave that way?

[@Lifeat39000ft]

Hi. I have a question. I am on Catalina and wish I wasn’t! Some of my apps won’t work. If I install Mojave like you explain will I be able to access the data in the old apps even thou they are on a different partition? Hope this makes sense. Cheers Damian

[@AppleNinja]

Hey Damian, Yes you should have access to all the files on the other partition as it just looks like another drive when not booted to it. Let me know how it goes! Good luck and Cheers!

[@brianwiltsey]

Good video! I have High Sierra and will be doing the easy steps to create a volume with Catalina. I want to be able to use recent versions of Logic Pro, etc on Catalina but still keep my outdated plugins with an older version of logic on the high Sierra volume. My question is how does backing up with time machine on an external hd work with 2 sep volumes? Will time machine allow to me keep 2 sep backups for each system on the 1 external hd? Thnx!

[@AppleNinja]

Hey Brian, You can use the same drive, but you will want to partition the drive and use one partition for the one macOS Time Machine Backup and the other partition for the other macOS Time Machine Backup. Hope this helps bud, have an awesome day!

[@Spencerk468]

Can I dual boot mojave and mojave? (Yes I know that I could just make two separate accounts but I have my reasons to dual boot.)

[@AppleNinja]

Yes you absolutely can Dual boot Mojave and Mojave!

[@remalistochastis]

Hi, thanks for sharing your experience. I have a question. Why should we go the more complex way using command lines etc. when it is simpler to use the installer? Is there a difference in the and result? 2. Catalina final is released (also in Greece) today. Since I have my MacBook Pro for working is that bootable USB disk useful for reinstalling the Mojave if an app that I use does not work? (although I only need Adobe CC wich should actually work and I have the latest versions and I also use Garageband and imovie wich should also work). Only some free GarageBand plug ins instruments etc. might not work but it is not important. A lot of thoughts. Greetings from Greece.

[@AppleNinja]

Hello Nikos and Greece! Question 1 Reply: The end result is ultimately the same, but if you learn the command line way it can help. For instance if you have an issue where the Mac does not boot into the Mac OS, but can get into the recovery partition. Then you could add a new volume and install the Mac OS on that new volume for troubleshooting the bad MacOS volume. I have also seen where Disk Utility has issues and creating Volumes from the Command line were necessary. Also if you ever want to script it and automate it, then the command line is the way to go. Question 2 Reply: You cannot downgrade the macOS from Catalina to Mojave, so you'd have to wipe it and install a fresh copy of Mojave from your USB stick or some other fashion. If you have all the Adobe installers and are not afraid of having to reinstall everything from scratch, then I would just verify your Apps are compatible with Catalina according to a site like roaringapps.com and proceed with the upgrade. Make sure to backup your files before any upgrade to your running macOS just to be safe. We had numerous people upgrade to Catalina yesterday and all our apps are looking good so far, which is fantastic. Also note that T2 Chip Macs cannot boot from a USB Stick and install the macOS unless you change the Secure Boot options in Recovery Partition to allow booting to external media. But you can use the startosinstall command from the installer on a USB stick, just not booted from it. I hope this helps Nikos, take care.

[@remalistochastis]

@@AppleNinja Thanks a lot!

[@omfgitsgone1978]

You're a Beast, Liked and Subbed

[@MrSoftfreak]

I tried to dualboot High Sierra and Big Sur. I am running a Macbook Pro early 2015 model. I created a partition (not volume) where I wanted to install the new macOS Big Sur. However, after installation is done, I can only see Big Sur startup disk in the boot menu and High Sierra is disappeared. It doesn’t even show in disk utility. It just shows that an unknown partition is sitting inside the drive, which was basically the partition containing High Sierra prior to Big Sur installation. I can’t access data on that drive partition at all! Is there a way I can regain access to my High Sierra partition or at least rescue the data I had on that partition? The High Sierra was filevault protected.

[@AppleNinja]

Is the Volume Mounted on the Desktop? If not go into Disk Utility and select the Volume on the left and click mount. You should be able to mount it and access the data.

[@angusting7018]

Good day. My macbook storage is 250gb and I use 210gb for my Catalina and 40gb for my Mojave, but then I realised that 40gb wasnt enough for my Mojave partition, so is there any way I could expand the Mojave partition capacity? Thanks :)

[@mealphamale]

@The Apple Ninja I see: - Macintosh HD - Macintosh HD - Data Which one to choose?

[@AppleNinja]

Hey Mohammed, the 2 volumes you see there are for a 10.15 Catalina macOS. The macOS Data is on Macintosh Hd and the users data is on Macintosh HD Data. You would not choose either of these for anything. You’d want to either create a new volume to install a macOS on or wipe the root level partition above the Mac HD and Mac HD Data volumes in the list and then install onto that. Since you have Catalina on the Mac are you trying to create another Catalina Volume or a Mojave Volume?

[@mikebooker2559]

Great vid! quick question i just upgraded to catalina/using partition can i install and run mojave?(or was this answer in video)thanks

[@AppleNinja]

Hey Mike. So you now have a Mac with Catalina only and you want to make a new partition with Mojave on it? I just tried to do this and was unsuccessful. I tried 3 different ways. First by running the Mojave installer while in the Catalina OS and it said it could not be run. Second attempt was using the recovery partition and the Terminal app with the Mojave installer on the Catalina Volume and it just sat there. Third way was from recovery again but with the Mojave installer on a USB stick and calling the startosinstall Command, still no go. Last attempts will be to see if letting the recovery partition do the reinstall with the OS that came on the Mac. Let me know if this is what you are talking about or if it was something else.

[@mikebooker2559]

@@AppleNinja thanks for responding/i figured it out though/had to create a partition then use bootable drive to install mojave/so now i have catalina and mojave/reason i needed mojave is to run my pro tools, downloading now(fingers crossed)

[@darrenb432]

The Apple Ninja hi I’ve tried all these options too, nothing happening. I’ll try create a partition instead of a volume and boot from a bootable disk and see if it works. Have you got any advice? Thanks.

[@RokzBeatz]

I'm still on High Sierra ( mac pro retina 2013 model ) when I go to my app store it tells me to update. I dont want update to Catalina I'd rather update to mojave. But I cant find mojave in the store ? Can I still update from high sierra to mojave ?

[@AppleNinja]

Yep you can. Here is a link that should allow you to download it. Happy Friday! itunes.apple.com/us/app/macos-mojave/id1398502828?ls=1&mt=12

[@RokzBeatz]

@@AppleNinja thank you ! Will there be any problems updating from high sierra ?

[@RokzBeatz]

@@AppleNinja it says open ? in my apps i have an app that says install Mojave so i must already have it downloaded will that app still work ?

[@alejandrocanales7291]

Hey Man, im on Catalina and it’s giving me a headache. I want to dual boot Catalina and Mojave. Will I be able to do this adding a volume and installing Mojave on it?

[@AppleNinja]

Hey Alejandro! You will need to create a bootable USB Stick with Mojave on it, then boot to the Mojave USB to install Mojave onto the other Volume you have. While booted to Catalina you cannot install Mojave because the installer will fail. You can though make a USB Bootable Mojave Drive and boot to it to get what you want done. Here are the Steps from Apple to create the USB Bootable Media: support.apple.com/en-us/HT201372 Let me know if you get it or run into issues.

[@ffleischer]

Great video! Do you know how to resize Bootcamp disk (increase bootcamp, decrease macOS) in Catalina? Without reinstalling bootcamp of course, this could be a useful video.

[@AppleNinja]

Hey Fritz, It is possible with software from Paragon, but I have never used this, so I cannot say how well it would work. I would only feel comfortable running it with a good backup of each OS. The way I would do it is make a full backup .iso of the windows partition and store it on the Mac. Then blast away the Boot Camp partition and re-install, but I have not performed this way either, so make sure you backup! If I can come up with a good way I will definitely make a video. Have an awesome weekend Fritz, take care!

[@WrvrUgoThrUR]

I was with this for a while, but too complex. I just want a partition with an older OS. Gotta be a simpler way. [EDIT] found it here: kzbin.info/www/bejne/eWS1Y6uKhbGbncU

[@hasoonnine]

could i still do this if im using mac os sierra?

[@AppleNinja]

It might be better to upgrade your MacOS Sierra (HFS) to High Sierra, which would convert it to APFS, then both would be APFS for writing files between the OS’s. I have not done a dual boot with Sierra and Catalina, but I think it might work just fine.

[@hasoonnine]

@@AppleNinja thank you so much, i appreciate the help