building Nix...
building the system configuration...
these derivations will be built:
  /nix/store/y25c01qzlvkrd5bqaghbkchzlfiz7sx1-kernel-modules.drv
  /nix/store/2jiz6y3lmjv00ncjmsqkv9dbgszp0sfa-kernel-modules-shrunk.drv
  /nix/store/zw3k2x58nhvgbljb34vn3sl233kfa14a-xserver.conf.drv
  /nix/store/3qgi54cnvv4mc0pcm1glyb8v51nsqj7n-xserver-wrapper.drv
  /nix/store/45xiy17975pkiz8aihymwkpz27dlbbjx-stage-1-init.sh.drv
  /nix/store/binq8vf1z8zza5z9xssd09czy444d9ib-nvidia-persistenced-340.107.drv
  /nix/store/scxhamg5kf2315vvv1br9qqmkdikrfgg-nvidia-settings-340.107.drv
  /nix/store/nnlm71pfn8031c92la44v5yg23vxyvq5-system-path.drv
  /nix/store/qhy3b3skmf016nxccck1fib65y9kaa65-dbus-1.drv
  /nix/store/6mjdj76pl4z93pfy9bixzh2c87kf8l52-unit-dbus.service.drv
  /nix/store/rgsdr9mkwjzpsn9k79sqn6ghag1lfn1x-unit-dbus.service.drv
  /nix/store/ad7d1izfn7ja4csf5b434qj5lq2963ky-user-units.drv
  /nix/store/ap0ppqkjc9lavr7myak6f4smyxsg218h-unit-systemd-fsck-.service.drv
  /nix/store/bvswvwmj62vbjk7xq8rwaigy8zpvimkb-sddm.conf.drv
  /nix/store/hrhva5r8jj7avig8av1djc2yrhwl38bj-initrd.drv
  /nix/store/m55agzfwmj8b8zfpmdx8nd86q099ag5s-unit-polkit.service.drv
  /nix/store/js31xiyy0c1294f60mjmy5m0rwcr5mdi-system-units.drv
  /nix/store/lg5f30jbkqn11k64w74bv7skdbp679qk-etc.drv
  /nix/store/rg8w7wcq9rfzc26jfm8nkcvn71vi1lh0-opengl-drivers.drv
  /nix/store/xnh0ahsnmgpgpndgyd8qxg2gc53wfxkr-nixos-system-UFO-18.09.2327.37694c8cc0e.drv
building '/nix/store/y25c01qzlvkrd5bqaghbkchzlfiz7sx1-kernel-modules.drv'...
building '/nix/store/rg8w7wcq9rfzc26jfm8nkcvn71vi1lh0-opengl-drivers.drv'...
building '/nix/store/binq8vf1z8zza5z9xssd09czy444d9ib-nvidia-persistenced-340.107.drv'...
building '/nix/store/scxhamg5kf2315vvv1br9qqmkdikrfgg-nvidia-settings-340.107.drv'...
collision between `/nix/store/l9y5yaij1gcyf94cb1s3n1yrj1dvy7l5-nvidia-x11-390.87-4.14.105-bin/lib/xorg/modules/libnvidia-wfb.so' and `/nix/store/wq1pmv8zw84sfs30wvg5d58f5506fm2g-nvidia-x11-340.107-4.14.105-bin/lib/xorg/modules/libnvidia-wfb.so'
created 2 symlinks in user environment
builder for '/nix/store/y25c01qzlvkrd5bqaghbkchzlfiz7sx1-kernel-modules.drv' failed with exit code 25
cannot build derivation '/nix/store/xnh0ahsnmgpgpndgyd8qxg2gc53wfxkr-nixos-system-UFO-18.09.2327.37694c8cc0e.drv': 1 dependencies couldn't be built
error: build of '/nix/store/xnh0ahsnmgpgpndgyd8qxg2gc53wfxkr-nixos-system-UFO-18.09.2327.37694c8cc0e.drv' failed