No entry sign after booting from usb

[vcs]

Hi everyone,
I've just got the new iMac (2019 model) and as I always do after getting a new computer, I install the os system from scratch via bootable usb.
I create using createinstallmedia a Mojave bootable usb.
I insert the usb pen drive, then start the iMac with option key presses, choose to boot from the installer usb and after that I got the no entry sign.
I'm unable to install a clean copy version of Mojave because of that.
I've tried the same bootable usb on my mom's MacBook Pro (2018) and no problem...
Any help anyone?
Thank you very much!

 

[CoastalOR]

First, is the Mojave used 10.14.4 for the USB Installer?

If yes, then it could be that the new 2019 iMac shipped with a special version of 10.14.4 just for the new iMac that is not available for download. Contact Apple Support.

 

[Fishrrman]

Coastal has the answer.

It looks like the version of "10.14.4" that ships with the new iMac is NEWER THAN the latest version of 10.14.4 that is posted and publicly-available from Apple's servers.

There is no need to "do what you've always done". There is NO benefit to be gained by attempting to re-install the OS over the factory install.

In fact, you're finding out that -- right now -- it's IMPOSSIBLE to do so.

Wait until 10.14.5 is released.
Then it will work.

 

[vcs]

Yes, the 10.14.4 version of Mojave is used for the USB installer.
What Fishrrman says it means it's not possible to downgrade from a Mojave to high Sierra for example...
as far as I know, it's possible to install from a bootable usb an older macOS version over a newer version, am I right?
Are you guys sure it's not something about some permission you have to give in order to boot from an external usb??
Thank a lot for your help and time.

 

[CoastalOR]

Yes, the 10.14.4 version of Mojave is used for the USB installer.
What Fishrrman says it means it's not possible to downgrade from a Mojave to high Sierra for example...
as far as I know, it's possible to install from a bootable usb an older macOS version over a newer version, am I right?
Are you guys sure it's not something about some permission you have to give in order to boot from an external usb??
Thank a lot for your help and time.

The new 2019 iMac only supports Mojave and above. It ships with Mojave. It was built and released (19 March 2019) with a newer processor (8th & 9th generation intel) after Mojave was released in September 2018.

It does not support High Sierra. It is not possible to downgrade to High Sierra using a USB installer.

 

[naerct]

Not surprised about Mojave not booting with the new iMacs. Every time I switch from 13 to 14, it takes a while for the 2 boot drives to communicate more than they ever had to before. Then the boot time is about double to get the other OS loaded and a sign-in screen. When I saw this happened every time, it was evident that Apple was up to something. i can't imagine how fast those new iMacs are, but I may never need one as I'm retired and just did a CPU upgrade to a 12-core 3.33 with the 1333 RAM. With the addition of a couple of 3GB/s NVMe SSDs, operating multi-core software may not be slower than with the 2019 iMac since my cMP has triple the cores. My upgraded 2009 cMP may never get to 10.15, but that shouldn't be an issue for my lifetime. Apple has done a lot worse, just imagine you have a high end Nvidia video card that stopped working after High Sierra...

 

[toneofark]

Secure boot is the issue. By default, newer Macs with the T2 security chip won't allow booting from external media. When you turn on your Mac, press and hold Command-R when you see the logo, to boot into recovery. Go to Utilities and select Startup Security Utility and make the necessary changes.

 

[naerct]

No wonder I wasn't aware, my youngest Mac is a 2012 MBP. That's no excuse, thanks for that important security information. A good measure in some situations. Probably not much of a theft deterrent, but a good way to prevent intrusions. That won't help with a Mac Pro with 6 SATA bays and 3 open PCI slots, unless you put a big padlock on the door... which probably won't fit anyway. In my 4-core, I have an old SATA2 SSD with the OS in the unused optical bay, just in case the normal boot fails. Is that different than the new iMacs with the built-in OS????? But I have clones everywhere. I have a bootable volume on the five disk RAID5, as it only takes 100GB. I also have a Sonnet card with 2 500GB SATA SSDs onboard in a striped RAID, so that's another TB of fast drive space where I have partitioned off another clone of my boot drive. That gets just under 1GB/s reads and actually boots faster than my Samsung 960 boot drive with 2.7GB/s speed. I have speculated (without a clue, as usual) that Apple may be having both software and hardware keyed toward NVMe and away from SATA. I don't think the newest Macs even have a SATA bus, do they? I guess the ones with Fusion drives must. I can't believe they still sell them with those slow HDDs. My friend has all six of his SATA bays filled with SSDs, and two more OWC PRO 2TB SSDS on his Sonnet card which are twice as fast even without a RAID. I never knew a cMP could be so quiet. I don't think I need that extra security as I use File Vault encryption and you need it's key before it will boot anything (I hope).