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+# Using an RPI Zero as an USB drive to install operating systems
+
+If you install operating systems, then you might have suffered the annoyances of writing images to USB drives.
+To write an operating system to a USB drive, you must wipe the entire contents of the USB drive.
+So a USB drive can only contain a single operating system.
+
+There are alternatives:
+
+* iODD sells external USB drives that can emulate CDROM drives.
+* netboot.xyz and other netboot images can boot operating systems over the network.
+* Multiboot USB software like Ventoy or YUMI.
+
+## Using a Raspberry Pi Zero
+
+Linux devices can emulate USB mass storage devices (and other kinds of USB devices).
+
+However, powering a Linux device using a USB port might draw more current than it is safe, damaging the device powering the Linux device (e.g. a laptop you want to boot from USB).
+
+A simple option is getting a Raspberry Pi Zero (I used the 2 W model) with the [EP-0097](https://wiki.52pi.com/index.php/EP-0097) USB adapter.
+This should be safe.
+However, without any additional setup, the procedures I describe only work when using an always-on USB port.
+
+(Assembling the Raspberry Pi Zero into the USB adapter is straightforward.
+However, I was confused: you must mount the thin acrylic shield below the USB dongle extension board, then the thick shield over the board, then the Raspberry Pi.)
+
+1. Use the Raspberry Pi Imager to create a MicroSD card for your Raspberry Pi Zero, configuring remote access via SSH and your wireless network.
+1. Connect the Raspberry Pi with the adapter into an always-on USB port of the device you want to use.
+1. Stall the device boot process until you set everything up on the Raspberry.
+1. Connect via ssh over wireless to the Raspberry Pi.
+1. Download the image you want to use.
+1. Use the `rmmod` command to remove any modules starting with `g_`.
+1. Run `modprobe g_mass_storage file=/path/to/image`
+1. After running this command, the device should be able to boot the image.
+
+### Notes
+
+* You can run a command such as `while date ; do sleep 1 ; done` to monitor that the Raspberry Pi does not reboot or poweroff.