External bootable forms of macOS: a few questions

Thanks, everyone, for all your replies. It appears that what I proposed was by no means daft.

The reason for creating volumes on an external disk has been to avoid the carry-over of configuration settings and damaged files from my existing version of OSX when performing an OSX (now called macOS) upgrade or doing a Reinstall via Recovery. By downloading the macOS file from the Apps Store and subsequently booting or installing it from an external disk you can ensure that instead you get a clean install (preceeding the eventual install on to the Mac by an erasure of the Mac's boot volume).

I've invested in a good-quality external SSD for this purpose, the idea being that as Apple releases each new edition of macOS I'll be able to not only try out (without affecting my current OSX/macOS on my Mac) a clean version to see how it performs and whether it fits in with my requirements but also be able, with the Installer, to actually put the new edition permanently on to the Mac if things work out okay. Thus far, I've created four differently-named volumes (partitions) on the external disk, giving me the opportunity over the next year or two to deal with two different editions of OSX fairly readily. With one of the volumes, I've already been able to try out a clean Sierra (my current OSX harps back to Mavericks!), though I'm far from finishing my investigations of Sierra yet. I've made four volumes so that I can keep 'try-out' or test versions of Sierra and its eventual successor in two of them, and corresponding installers in the other two volumes.

Actually, a couple of other queries have come to mind. For making the Installer, I've used the 'installmedia' Terminal technique, but I understand that Terminal command line doesn't like names that contain spaces, and maybe also upper-case characters as well. However, I thought I read somewhere that you can get around that by enclosing the name with quotes. Here's the middle section of the Terminal command. Am I using the quotes in the correct places? INSTALL macOS1 is the name I've given to my Installer volume:

..... --volume /"Volumes/INSTALL macOS1" --applicationpath /......

Also, is it necessary to add 'no interaction' to the end of the line? What does 'no interaction' do, if anything?

Luis,

I got it slightly wrong, then? The first quotes should be before the forward-slash. Thanks for correcting me, and also for telling me about the alternative of using a back-slash. Is that a space after the back-slash and before macOS1? It looks like it.

As for the link you gave, I've already been using that, but I wasn't aware that it pointed out anything concerning back-slashes in place of spaced names.

Presumably, Terminal command-lines are happy to accept uppercase? And what about 'no interaction'? In the link about bootable installers there's no sign of 'no interaction' and yet, in older articles I've read, 'no interaction' is added at the end of the line.

John et al,

All done! I've now got the Installer on my selected external disk. I used the more straightforward method of simply typing out the full command line in Terminal, being of course very careful to get it precisely right. After that, it all completed extremely quickly.

Like you said, it doesn't really matter what name you initially give to the volume, because the process of putting the Installer on to that volume causes automatic renaming of the volume to "Install macOS Sierra".

Anyway, this now means that, if after testing Sierra with my other 'swap-out' version of it (also put on to an external disk), I find things satisfactory I can use the Installer to put a clean version of Sierra permanently on to my Mac's internal disk (rather than just doing a standard upgrade and inheriting bad files and bugs from my former operating system). As you'll appreciate, having the Installer on an external disk means that the existing boot volume on the Mac can be erased before finally executing the Installer.

My testing of Sierra (StartUp swap-out with my existing operating system) may well involve me, on and off, in some days of work, but if at the end of it I'm satisfied with how Sierra performs, then I'll go ahead and use this Installer to put Sierra permanently on to my Mac's internal disk. The same will be the case when a successor to Sierra comes along. The exact procedure for that is, however, not 100% clear to me. As far as I've been able to gather, what I'd need to do is the following:

1. Re-start the Mac with the external Installer volume connected and the Opt key held down.

2. This should give a screen showing all bootable disks, and the "Install macOS Sierra" one should be selected.

3. This apparently will open a list of settings concerning the type of installation required.

4. For a clean install, opt to open Disk Utility and, there, erase the boot volume on the Mac's internal disk.

5. Return to the "Install macOS Sierra" volume and, from the list mentioned in 3, select specifically "Install a new copy of macOS".

6. The install of the clean copy should then proceed.

You might have to correct me on this but I don't think steps 1 - 6 involve putting the Mac into Recovery but instead merely giving access to something akin to macOS Utilities. In contrast, getting into the Recovery Partition usually means restarting the Mac with the R key held down. But we don't want Recovery (Reinstall or an Internet Recovery) in this instance; what we're wanting is a clean install. In any event, Reinstall or Internet Recovery would simply re-instate all the bad files and bugs. So, as far as I can see, at Step 1 I'd need to hold down Opt instead, and then follow procedure along the lines of 2 - 6.

I've never seen a published description, beginning to end, of a clean install like this, and of course I can't at present confirm whether the presumed steps 1 - 6 are correct. I'll only ever find out when I've actually done it - which might not be for a few weeks yet. But perhaps you or others who may have performed a clean install at some stage in the not-so-distant past can say whether my procedural stages 1 - 6 are roughly correct?

I may be wrong about this but I suspect that the main reason users choose to test and then later install a new edition of macOS from an external disk in this manner is because, for one obscure reason or another, they've been having longterm unresolvable issues with their current edition and now want to upgrade but avoid bringing those problems with it. These two separate methods for putting a bootable new edition on to one or more external disks - one enabling swapout testing, the other facilitating permanent installation of the OS on to the Mac's internal disk - enables you to do this. Before, I've used Recovery and Internet Recovery, but found that they merely reinstated the issues and my personal settings; these two external, but local, methods sidestep that. Time Machine, when used in the standard way, can only of course restore what you had before and so unless you happen to have had an absolute virgin edition of the required OS somewhere on the TM disk, restoring from TM will merely restore all the damaged files/superfluous files/wrong user settings, etc again. It's been hinted in one or two articles I've seen, however, that post install of the clean OS, personal settings can be restored en bloc from TM into that clean edition, if required. Perhaps that's an option that pops up toward the end of the clean install? With a standard TM restore (ie. not involving booting anything from external disks), I've in recent times certainly encountered automatic restoration of all my e-mail folders and their contents, and was jolly pleased for the offer of it by TM.

John (et al),

My references above to TM have been to the 'standard' way of using it for full restorations. But in retrospect your comment, John, about using TM in the context of clean install, has caused me to think further about this.

So, are you saying then that, when you execute "Install macOS Sierra" (or whatever the required OS is) and it asks for the destination disk, one of the permitted disks is the TM disk (if you happen to be using Time Machine and have TM on an external disk)? Thinking about it, there seems to be no particular reason why it wouldn't be offered, is there? After all, the TM disk would, by definition, already be bootable, and normally when a TM full restore is done the Mac's boot disk gets automatically erased just prior to the restore. I could see therefore that that would be a way of having the equivalent of "Install macOS Sierra" but without the need to invest in an additional external disk. If this is the case, then all I can say is 'Clever stuff!'. TM is not without its failures, though, and so I'm glad I've put my clean Install Sierra on to a totally separate external disk. Always good to have alternatives.