Well, I am turning this into a bug report, since it still occurs with the latest git commit ac1a9ce8b07f3b80900ee08436ff6e683e8dc195 . This is the result of "./pre-inst-env guix system reconfigure ...", where "..." is my configuration file: ... creating nginx log directory '/var/log/nginx' creating nginx run directory '/var/run/nginx' creating nginx temp directories '/var/run/nginx/{client_body,proxy,fastcgi,uwsgi,scgi}_temp' nginx: [alert] could not open error log file: open() "/gnu/store/pp71iff1qxwhh82vm34g18h9kmn0xrg5-nginx-1.13.9/logs/error.log" failed (2: No such file or directory) nginx: the configuration file /gnu/store/5ixkryw6jl32cm6d1g9jb8dm9rbz8csc-nginx.conf syntax is ok nginx: configuration file /gnu/store/5ixkryw6jl32cm6d1g9jb8dm9rbz8csc-nginx.conf test is successful `/gnu/store/zchh8s3r1bbmia3zfxsyhsz3c4b9fmps-openssh-authorized-keys/root' -> `/etc/ssh/authorized_keys.d/root' `/gnu/store/zchh8s3r1bbmia3zfxsyhsz3c4b9fmps-openssh-authorized-keys/andreas' -> `/etc/ssh/authorized_keys.d/andreas' guix system: loading new services: user-homes term-auto nginx... shepherd: Evaluating user expression (register-services (primitive-load "/gnu/st?") ?). guix system: error: exception caught while executing 'eval' on service 'root': find-long-options: unbound variable Installing for i386-pc platform. /gnu/store/1dnbfda2p1bxwyl0rcm96ka9pmi0wb88-grub-2.02/sbin/grub-install: warning: disk does not exist, so falling back to partition device /dev/xvda2. /gnu/store/1dnbfda2p1bxwyl0rcm96ka9pmi0wb88-grub-2.02/sbin/grub-install: warning: disk does not exist, so falling back to partition device /dev/xvda2. /gnu/store/1dnbfda2p1bxwyl0rcm96ka9pmi0wb88-grub-2.02/sbin/grub-install: warning: disk does not exist, so falling back to partition device /dev/xvda2. /gnu/store/1dnbfda2p1bxwyl0rcm96ka9pmi0wb88-grub-2.02/sbin/grub-install: error: cannot find a GRUB drive for /dev/sda. Check your device.map. guix system: error: failed to install bootloader /gnu/store/9iv63jm07klxvrr4fpwv6q5vpnca13ja-bootloader-installer The final error is "normal", since I am installing in a Xen virtual machine, where /dev/sda does not exist; it did not matter before. The real error occurs above, the "uncaught exception". But: # herd status nginx herd: service 'nginx' could not be found Then I do a # ./pre-inst-env guix system roll-back # herd status nginx herd: service 'nginx' could not be found Otherwise said, I can go back, but my previously running web server has definitely gone! How do I get it back? Andreas