How can I achieve this from either macOS Catalina or Windows 10? I can't seem to find a guide online. I've downloaded Mac OS X Snow Leopard Install DVD from the Internet Archive. Keep in mind that this is an .iso file, not .dmg.
I don't need a full step-by-step guide, just need to know how to format the drive (MBR/GPT?) and how to copy the .iso file to it.
Below are three methods. The first method, which involves the Disk Utility application, failed to work when tested using macOS Catalina 10.15.7 on an iMac (21.5-inch, Late 2013) 2.9 GHz Quad-Core Intel Core i5. User John Mark Harrell's answer confirms this is also true when using Big Sur on an unspecified Mac. So the OP should probably try the second method involving the use of the dd command or the third method involving Balena Etcher.
This was tested using an iMac (21.5-inch, Mid 2011) 2.5 GHz Intel Core i5 with MacOS High Sierra 10.13.6 installed. The flash drive needs to be at least 8 GB in size. The Snow Leopard ISO file was the same as discussed in this answer, which should be the same ISO you have linked to in your question.
Use the Finder application to mount the Snow Leopard ISO file.
Use the Disk Utility application to erase the flash drive, as shown below. I chose the default name Untitled. Finally, click on the Erase button.
Highlight the name Untitled, then click on the Restore button on the top of the Disk Utility application window. In the popup window, select restore from Mac OS X Install DVD, as shown below. Finally, click on the Restore button in the popup window.
Note: This flashdrive will be using the Apple Partition Map scheme. This differs from the flash drive created using the Disk Utility, which used the Master Boot Record scheme. In other words, there is more than one way to create a USB flash drive installer from a Snow Leopard ISO file.
The steps below are for OS X and macOS.
Use the command given below to determine the identifier for the flash drive.
diskutil list
Enter the commands given below to create the USB flash drive installer. Here, an assumption is made that the ISO file name is snow leopard install.iso and the file resides in your Downloads folder. Also, an assumption is made that the identifier is disk2. If necessary, make the appropriate substitutions.
DISK=disk2
diskutil unmountdisk $DISK
sudo dd if="$HOME/Downloads/snow leopard install.iso" of=/dev/r$DISK bs=1m
The steps below are for Linux.
Use the command given below to determine the name for the flash drive.
lsblk
Enter the command given below to determine if any volumes on the flash drive are mounted. If there are mounted volumes, then use the sudo unmount command to unmount them before proceeding. Here, an assumption is made that the name for the flash drive is sdb. If necessary, make the appropriate substitutions in the rest of the steps.
mount | grep /dev/sdb
Enter the command given below to create the USB flash drive installer. Here, an assumption is made that the ISO file name is snow leopard install.iso and the file resides in your Downloads folder. If necessary, make the appropriate substitutions.
sudo dd if="$HOME/Downloads/snow leopard install.iso" of=/dev/sdb bs=1M
Note: Any version of Windows compatible with Balena Etcher should make an appropriate substitution for Windows 10. User John Mark Harrell has also posted an answer verifying macOS Big Sur can be substituted.
Download Balena Etcher to Windows. This answer was testing using the portable version, which can be executed without having to be installed. The file downloaded was balenaEtcher-Portable-1.7.3.exe.
Use Etcher to flash the image stored in the ISO file to the USB flash drive. When testing the following pop-up appeared.
The image does contain an Apple partition table, which is not recognized by Etcher. Since this check for a partition table is not required, the message can be ignored. Select the Continue button.
I couldn't find a method that worked as Disk Utility doesn't cooperate with OS 10.6 .dmg or .iso files, the instructions above might work on older versions of macOS, but I couldn't get it to work on Big Sur. But then I discovered that the same method I've been using to create bootable linux thumb drives works with the 10.6 .iso AND .dmg (depending on which one you have), and it's way easier and works on any operating system (mac/windows/linux).
Be sure to use a standard installation DVD .dmg or .iso, some of these are copied from the "grey" disk, which means they're attached to a specific machine and won't allow you to install even though you can still boot into it successfully.
As another user noted, the Balena Etcher method works great on a Mac. On my 2021 MacBook Pro (with M1 Pro chip), I created a bootable OS X Snow Leopard USB drive using a .DMG of Snow Leopard I downloaded on the internet. And then installed Snow Leopard on a 2009 MacBook Pro without a hiccup.
You need a USB disk with 8 Mb at least
Download BalenaEtcher from https://www.balena.io/etcher#download-etcher
Download an .iso or .dmg file from https://archive.org/details/snow-leopard-install_202112
Install BalenaEtcher, select image: a .iso or .dmg file A warning will pop up about how it's missing a partition table, Continue and bypass the warning. Select drive: the usb drive and press Flash.
Thats all folks. Works great.
i used balena etcher on High Sierra to flash the usb, an just when it finished it said something like the computer couldn't read the inserted disk; then when i restarted while holding option, the usb didn't appear. does anybody know the solution?
