bug#30706: Nginx service fails

[Andreas Enge]

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