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NixOS on ARM through QEMU is possible, by using qemu-system-arm on QEMU's 'virt' machine, and the u-boot image for qemu.

Note: [u-boot currently requires highmem=off for PCI to work], so you won't be able to use more than 2GB of RAM.

Board-specific installation notes

Required images

First get some recent sd-image-armv7l-linux.img and uboot-qemu_arm_defconfig-*_u-boot.bin as described the main NixOS on ARM page.

Creating qcow image

Convert the sd card image to qcow, and resize it a bit:

qemu-img convert -f raw -O qcow2 sd-image-armv7l-linux.img sd-image-armv7l-linux.qcow2
qemu-img resize sd-image-armv7l-linux.qcow2 +5G

Booting using qemu

The following command will boot QEMU's 'virt' machine with u-boot and the converted sdcard image, exposing four cpu cores and 2GB of RAM:

qemu-system-arm -machine virt,highmem=off -bios uboot-qemu_arm_defconfig-2018.03_u-boot.bin -drive if=none,file=sd-image-armv7l-linux.qcow2,id=mydisk -device ich9-ahci,id=ahci -device ide-drive,drive=mydisk,bus=ahci.0 -netdev user,id=net0 -device virtio-net-pci,netdev=net0 -nographic -smp 4 -m 2G

U-Boot 2018.03 (Mar 13 2018 - 12:02:19 +0000)

DRAM:  2 GiB
WARNING: Caches not enabled
In:    pl011@9000000
Out:   pl011@9000000
Err:   pl011@9000000
Net:   No ethernet found.
Hit any key to stop autoboot:  0 
scanning bus for devices...
Target spinup took 0 ms.
SATA link 1 timeout.
SATA link 2 timeout.
SATA link 3 timeout.
SATA link 4 timeout.
SATA link 5 timeout.
AHCI 0001.0000 32 slots 6 ports 1.5 Gbps 0x3f impl SATA mode
flags: 64bit ncq only 
  Device 0: (0:0) Vendor: ATA Prod.: QEMU HARDDISK Rev: 2.5+
            Type: Hard Disk
            Capacity: 7137.4 MB = 6.9 GB (14617528 x 512)

Device 0: (0:0) Vendor: ATA Prod.: QEMU HARDDISK Rev: 2.5+
            Type: Hard Disk
            Capacity: 7137.4 MB = 6.9 GB (14617528 x 512)
... is now current device
Scanning scsi 0:1...
Found /extlinux/extlinux.conf
Retrieving file: /extlinux/extlinux.conf
847 bytes read in 7 ms (118.2 KiB/s)
1:	NixOS - Default
Enter choice: 1:	NixOS - Default
Retrieving file: /extlinux/../nixos/b44d5kfyaixzkzy780br46ls3812cfx3-initrd-initrd
7084057 bytes read in 122 ms (55.4 MiB/s)
Retrieving file: /extlinux/../nixos/ajja3hfl2p4dadbg93rrs0zqrclisrwj-linux-4.16.1-zImage
6550016 bytes read in 112 ms (55.8 MiB/s)
append: systemConfig=/nix/store/km910m22ibjl6rjzfjiivn2mp71d86d6-nixos-system-nixos-18.09.git.1034aa8e9cb init=/nix/store/km910m22ibjl6rjzfjiivn2mp71d86d6-nixos-system-nixos-18.09.git.1034aa8e9cb/init loglevel=7 console=ttyS0,115200n8 console=ttymxc0,115200n8 console=ttyAMA0,115200n8 console=ttyO0,115200n8 console=ttySAC2,115200n8 console=tty0
Kernel image @ 0x40400000 [ 0x000000 - 0x63f200 ]
## Flattened Device Tree blob at 40000000
   Booting using the fdt blob at 0x40000000
   Using Device Tree in place at 40000000, end 40012fff

Starting kernel ...

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 4.16.1 (nixbld@localhost) (gcc version 7.3.0 (GCC)) #1-NixOS SMP Sun Apr 8 12:29:52 UTC 2018
[    0.000000] CPU: ARMv7 Processor [412fc0f1] revision 1 (ARMv7), cr=10c5387d

<<< Welcome to NixOS 18.09.git.1034aa8e9cb (armv7l) - ttyAMA0 >>>

The "root" account has an empty password.  

Run `nixos-help` or press <Alt-F8> for the NixOS manual.

nixos login: root (automatic login)

Note: first boot might take a bit longer, due to the root file system being resized to the disk size.