env

My Nix environment. Once you have Nix installed, the first step is to clone this repo:

nix-shell -p git gh --run "gh auth login && gh repo clone samestep/env ~/github/samestep/env"

There are separate configurations for the three different machines I use.

NixOS

This machine has an x86 CPU and an NVIDIA GPU, and runs NixOS.

Run these commands to setup the NixOS configuration:

cp /etc/nixos/hardware-configuration.nix ~/github/samestep/env/nixos/nixos/
sudo rm /etc/nixos/*
sudo ln -s ~/github/samestep/env/flake.nix /etc/nixos/flake.nix
sudo nixos-rebuild switch
sudo nix-channel --remove nixos

Then run these commands to setup the Home Manager configuration:

ln -fsT ~/github/samestep/env ~/.config/home-manager
nix run ~/github/samestep/env#home-manager switch

You may need to log out and back in to see everything installed in the GNOME applications launcher.

macOS

This machine has an Apple M1 chip and runs macOS.

Enable flakes by making sure this line is present in /etc/nix/nix.conf:

experimental-features = nix-command flakes

Then run these commands to setup the Home Manager configuration:

nix run ~/github/samestep/env#home-manager switch
rm -r ~/.config/home-manager
ln -s ~/github/samestep/env ~/.config/home-manager
nix run ~/github/samestep/env#home-manager switch

Ubuntu

This machine has an x86 CPU and an NVIDIA GPU, and runs Ubuntu.

Enable flakes by making sure this line is present in /etc/nix/nix.conf:

experimental-features = nix-command flakes

Next enable user namespace creation by making sure the line kernel.apparmor_restrict_unprivileged_userns = 0 is present in some file under /etc/sysctl.d/, e.g. by running this command:

echo 'kernel.apparmor_restrict_unprivileged_userns = 0' | sudo tee /etc/sysctl.d/20-apparmor-donotrestrict.conf

Then run these commands to setup the Home Manager configuration:

ln -fsT ~/github/samestep/env ~/.config/home-manager
nix run ~/github/samestep/env#home-manager -- switch --impure

Docker (x86 and ARM)

This repo also contains dedicated Home Manager configs for use in an Ubuntu Docker container; for instance:

docker build . -t agent
docker create agent sleep infinity

Then in VS Code, start the container and attach to it.

libvirt

The Docker configs can also be used for virtual machines. First make sure you have virt-manager, virt-viewer, and the libvirt NSS module installed, as they are in this repo's NixOS config. Then make sure you've started the default network:

virsh -c qemu:///system net-start default

You can also run this command so the default network starts automatically in the future:

virsh -c qemu:///system net-autostart default

Download an OS ISO like Ubuntu 26.04 and run this command to create a VM, tweaking the CPU/RAM/disk parameters as appropriate:

virt-install --connect qemu:///system --name sandbox-amd64 --vcpus 32 --memory 65536 --disk size=1000 --network network=default --cdrom ubuntu-26.04-live-server-amd64.iso

As a heads up, at time of writing, the only reason Ubuntu 26.04 works for me here is because I'm using an unreleased osinfo-db patch that adds support for it. You may need to use an image of an older OS instead.

That aside, here's what all the flags mean:

• the --connect setting makes the default network visible
• the explicit --name is used by the libvirt_guest NSS module for SSH
• --vcpus allows the VM to use all the cores instead of just two
• --memory is in MiB
• --disk size is in GB
• the --network setting is necessary for SSH to work after installation

When installing Ubuntu, in the "Storage configuration" step, increase the size of the ubuntu-lv device from 100.000G to the maximum allowed, which will depend on how much disk space you gave it. Then use these options in the "Profile configuration" step:

• Your name: Agent
• Your servers name: sandbox-amd64
• Pick a username: agent-amd64
• Choose a password: password
• Confirm your password: password

Check the "Install OpenSSH server" box in the "SSH configuration" step. Then once installation is finished, ignore the message saying to remove the installation medium, and just hit ENTER to reboot.

After rebooting, you can close the virt-viewer window; you won't need it again. Reconnect using SSH:

ssh agent-amd64@sandbox-amd64

The only reason for choosing a password at all was because the Ubuntu installer forces you to; first step after installation is to enable passwordless sudo:

echo "agent-amd64 ALL=(ALL) NOPASSWD:ALL" | sudo tee /etc/sudoers.d/agent && sudo chmod 0440 /etc/sudoers.d/agent

The next step is to reconfigure chrony so that it can readjust the VM's clock if it becomes wrong e.g. if the host machine reboots. Make this edit to /etc/chrony/chrony.conf:

-makestep 1 3
+makestep 1 -1

Note that the above may be unnecessary if you configure libvirt to shut down VMs when you shut down the host machine. That may be a good idea in general, since if libvirt only suspends and resumes the VMs when the host machine reboots, their DHCP leases can disappear from the host, forcing you to use an explicit IP address for SSH.

Then install Nix:

sh <(curl --proto '=https' --tlsv1.2 -L https://nixos.org/nix/install) --daemon

Enable flakes:

echo 'experimental-features = nix-command flakes' | sudo tee -a /etc/nix/nix.conf

After installing Nix you'll need to log back out and back in. Then clone this repo:

git clone https://github.com/samestep/env.git ~/github/samestep/env

And set up the Home Manager symlink:

mkdir ~/.config && ln -fsT ~/github/samestep/env ~/.config/home-manager

And finally set up the Home Manager config itself:

nix run ~/github/samestep/env#home-manager -- switch -b backup

Tart

This config can be used for macOS VMs created with Tart, which comes with the host-side macOS config in this repo. First, download a macOS image:

tart clone ghcr.io/cirruslabs/macos-tahoe-vanilla:latest tahoe-vanilla

By default, Tart gives the VM only 50 GB of disk space and access to half the CPU cores, so adjust those as appropriate:

tart set tahoe-vanilla --cpu 8 --disk-size 250

Next follow the steps to finish resizing the disk of a macOS Tart VM, starting by booting in recovery mode:

tart run --recovery tahoe-vanilla

Choose Options, then open the Terminal under Utilities. Delete the preexisting recovery partition:

diskutil eraseVolume free free disk0s3

Repair the disk:

yes | diskutil repairDisk disk0

And resize the system Apple File System container to use the new disk space:

diskutil apfs resizeContainer disk0s2 0

Shut down the VM, then reboot it:

tart run tahoe-vanilla

Since we're using the vanilla image, we still need to install the Xcode Command Line Tools:

xcode-select --install

That should pop up a dialogue which you need to accept. You'll also want to allow Ghostty's environment forwarding over SSH:

echo AcceptEnv COLORTERM TERM_PROGRAM TERM_PROGRAM_VERSION | sudo tee /etc/ssh/sshd_config.d/101-color.conf

Now shut down the VM again and reboot it once more, this time without graphics:

tart run --no-graphics tahoe-vanilla

Leave that running and SSH into the VM from a different terminal:

ssh admin@$(tart ip tahoe-vanilla)

The password is admin. Install Nix:

curl -fsSL https://install.determinate.systems/nix | sh -s -- install

You may need to start a new shell. Clone this repo:

git clone https://github.com/samestep/env.git ~/github/samestep/env

Set up the Home Manager symlink:

ln -s ~/github/samestep/env ~/.config/home-manager

And finally activate the Home Manager config:

nix run ~/github/samestep/env#home-manager switch