How do I make a disk image?

[Wingsley]

How do I take a pre-formatted software installer thumb drive and make a disk image for storage on a backup external hard disk?

I just bought a mail-order USB 3.0 thumb drive (all the thumbs for sale around here were USB 2.0) that I intend to use for bootable software installations. One of my first projects will be to use the USB 3 thumb to clean-install MacOS Sierra. I am following instructions from this MacWorld magazine article.

I want to be able to erase the USB 3 thumb and re-use it for other installation purposes. If I want to clean-install Sierra on another Mac in the future (a family member's MacBook), I have to keep the installer disk image in safekeeping on an external hard drive so I can retrieve it later. So I have to find out how to make a disk image of the installer that is now on the USB 3 thumb for safekeeping now, and to be able to retrieve it and reformat the thumb at a later date.

Any suggestions on how to do this are welcome.

 

[DeltaMac]

The installer app is what you want to keep stored.
You would be downloading your macOS installer app from the App Store.
It will automatically launch after the download completes. Quit the installer app, and save that app to another drive.
I have those downloadable installer apps saved to a couple of externals - everything from OS X 10.7 to 10.13 beta.

So --- no need to find out how to make a disk image, as it is part of the installer app that you would already have. Just copy that app somewhere, so you will know where it is the next time you want to create a bootable installer.

BTW --- there's not a real difference between USB 2 and USB 3 flash drives, none that you would really notice on a bootable installer, anyway.

 

[Wingsley]

Thanks for the info, DeltaMac.

The reason I'm going about it this way:

I am using the thumb drive as a bootable installer drive so I can clean-install Sierra on my iMac. I plan on using this thumb drive to also install Windows 10 and maybe Office 365 as well after I get up and running with Sierra.

After I'm done with all that, I will be clean-installing Sierra on a family member's MacBook.

That's why this thumb drive and the installer will come in handy.

 

[DeltaMac]

I have a 64GB thumb drive with every OS X system from 10.5 to 10.13 - each on separate partitions on that drive, so I can install OS X on virtually any Mac sold in the last 10 years or so.
(I don't like messing around with booting PPC Macs from a USB drive, but that is a possible "thing", too, so possible to install OS X back to G3 iMacs, back to original in '97/'98, as I do have images of Tiger (OS X 10.4) also.
All from the same flash drive.

Final suggestion. flash drives are cheap. Find a couple of 8GB flash drives, use one for Sierra, and the other for Windows, etc. Leave them as is, as the USB flash drives deteriorate (slightly) every time you erase the drives.

 

[chown33]

Final suggestion. flash drives are cheap. Find a couple of 8GB flash drives, use one for Sierra, and the other for Windows, etc. Leave them as is, as the USB flash drives deteriorate (slightly) every time you erase the drives.

I suggest getting SD or microSD cards, and a single SD-to-USB adapter. SD and microSD cards in suitable sizes are cheap.

The Transcend USB 3.0 card reader is under $10 at Amazon.
https://www.amazon.com/Transcend-microSDHC-Reader-TS-RDF5K-Black/dp/B009D79VH4/

I have this exact reader, and it works great.

 

[Wingsley]

Would it be okay to get a Class 10 SDHC card, or do they have to be SDXC cards? I already have a Sony SD/SDHC/SDXC card reader/thumb, plus my iMac has an SDXC card reader built-in.

 

[chown33]

Would it be okay to get a Class 10 SDHC card, or do they have to be SDXC cards? I already have a Sony SD/SDHC/SDXC card reader/thumb, plus my iMac has an SDXC card reader built-in.

Pretty much anything of the requisite capacity will work. Even slower cards will work, you'll just wait longer to copy things to and from. Or if you run the installer app directly from the card, it will take longer.

If you're making an actual bootable disk of the SD card, then speed matters a lot more. I've booted my 2012 MBPro from a 16GB microSD card that I simply had sitting around. I don't recall the version or speed rating, and I don't have the card available right now. It took a long time to boot, but it did work. I used a microSD-to-SD adapter card and the builtin SD reader. That worked about the same as the Transcend USB adapter, which tells me that the speed was constrained by the decrepitude of the microSD card, not the speed of the bus it was on.

I've also got a bootable OS on a 64GB SanDisk Extreme Pro, which has a class 10 rating, and "95 MB/s" printed on its label. This is roughly similar to the spinning disk, an HGST HTS721010A9E630. I don't use the MBPro extensively enough to warrant putting an SSD in it, but I'm sure any SSD would beat the pants off either the SanDisk SD card or the HGST spinner.

I have other SD cards with apps on them, which are infrequently used, so it's convenient to keep the app on the same medium as the files. They aren't Extreme Pro cards, but they work fine. Again, not as fast as an SSD would be, but practical for infrequent usage.

 

[Wingsley]

An idea occurred to me:

I could partition this new USB 3.0 thumb drive, which is 32 GB so it has plenty of capacity. I could have MacOS Sierra installer in one partition, a Windows 10 installer in another partition (if necessary), and Office 365's installer(s) in another partition, if warranted.

How do I set up partitions on this thumb drive? I'm embarrassed to admit it, but I've never done that before.

 

[chown33]

How do I set up partitions on this thumb drive? I'm embarrassed to admit it, but I've never done that before.

Disk Utility: Partition a disk

 

[DeltaMac]

Question: Can you make a bootable macOS installer partition, and also have a bootable Windows installer partition, both on the same device?

@chown33 - your linked article is for the old Disk Utility, when partitioning was still simple, and versatile.
I can't say the same about current versions of Disk Utility.
I always go back to a Yosemite boot, or older, do to multiple partitions on storage drives.