nixpkgs/nixos/doc/manual/installation/installing-usb.section.md

Booting from a USB Drive

For systems without CD drive, the NixOS live CD can be booted from a USB stick. You can use the dd utility to write the image: dd if=path-to-image of=/dev/sdX. Be careful about specifying the correct drive; you can use the lsblk command to get a list of block devices.

::: {.note} ::: {.title} On macOS :::

$ diskutil list
[..]
/dev/diskN (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
[..]
$ diskutil unmountDisk diskN
Unmount of all volumes on diskN was successful
$ sudo dd if=nix.iso of=/dev/rdiskN

Using the 'raw' rdiskN device instead of diskN completes in minutes instead of hours. After dd completes, a GUI dialog "The disk you inserted was not readable by this computer" will pop up, which can be ignored. :::

The dd utility will write the image verbatim to the drive, making it the recommended option for both UEFI and non-UEFI installations.