nix

reMarkable NixOS

Booting

The system is launched using a systemd soft-reboot. The nixctl script will mount the nixos directory on /run/nextroot. This will cause systemd to use it as a new root when rebooting. The NixOS stage2 init script at sbin/init will be started, booting the full NixOS system.

Advantages:

• No changes on reMarkable root partition.
• Full isolation between NixOS and main system.
• A simple reboot will restart into xochitl.

Disadvantages:

• NixOS doesn't manage the linux kernel.

Usage

To use nixos, build the config.system.build.image:

nix build .#nixosConfigurations.example.config.system.build.image

This will put a tarball in result/tarball/rm-nixos.tar.xz, which can be copied over and extracted on the remarkable 2:

scp result/tarball/rm-nixos.tar.xz root@<remarkable>:
ssh root@<remarkable>
> mkdir -p nixos
> tar -C nixos -xJf rm-nixos.tar.xz

Don't forget to create a separate directory before extracting, otherwise you'll pollute the home directory.

Now the system can be launched by starting the launch script, make sure to stop xochitl / rm2fb first:

# Should technically happen automatically as nixos Conflicts with this,
# but doesn't hurt:
> systemctl stop xochitl rm2fb
> ./nixos/nixctl launch

Now a new rm2fb server will be running, with an instance of yaft_reader that shows the kernel log, which is useful for debugging. To start NixOS, reboot into it. Each of these commands will do the same:

> systemctl soft-reboot
> systemctl reboot
> reboot

To exit NixOS, simply reboot again.

Wifi

nixctl copies your saved wifi networks over from xochitl's config on every boot, so it works out of the box on NixOS too. It copies both the wpa_supplicant-style wifi_networks.conf and any NetworkManager *.nmconnection profiles it finds; only the one actually in use is picked up, based on which config.nix option you enable, matching your xochitl version:

• networking.wireless.enable = true; for xochitl < 3.28 (wpa_supplicant).
• networking.networkmanager.enable = true; for xochitl >= 3.28 beta (NetworkManager). Add your login user to the networkmanager group, otherwise it can't talk to NetworkManager over D-Bus.

Installing

The nixctl install command will install NixOS so that it automatically starts when the system is rebooted from xochitl. The nixos uninstall command should remove all traces from the system partition.

Virtual Machine

A QEMU based vm is available at config.system.build.vm:

nix build .#nixosConfigurations.example.config.system.build.vm
./result
# Wait for boot, login as root

This VM boots into NixOS directly. To boot into xochitl first use config.system.build.vm-xochitl.

TODO

• Test wpa_supplicant conf copy.
• Test nixos-rebuild from host.
• Split ./configuration.nix into separate modules.
• Create xochitl chroot.
• Re-create wrapWithPreload, rm2-stuff program modules.
• Write rocket launcher systemd unit.
• Rework launch, allow install.
• reMarkable document sync.
• Fix koreader spamming 'WARN Polling for input events returned an error:'
• Make vm that starts rm2-emu automatically.
• NixOS tests.
• Make xochitl run as a user?
• Minimize size
• Drop nixos tools, don't use -ng to lose python dep.
• Correctly start user session for Rocket.
• Usb ethernet.