I'm not real sure on this one, let us know if you find more details. I didn't find much on a quick google search, but I thought that Rails would automatically use the current request's subdomain/domain so you wouldn't have to do anything.
Well I feel dumb. I didn't have Image Magick - sudo apt install imagemagick - on the server; once that was installed, all was good. Perhaps adding a mention of that in your tutorial on deploying to Ubuntu 18.04. Thank you for all your work on this site; I've learned a ton and $19 a month is a steal for the value you offer. Thanks!
Ah, that'll get you! Good idea about adding that. It's pretty common, either that or one of the alternatives like libvips that's supposed to be faster.
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