from the documentation on
https://answers.launchpad.net/calibre2opds/+faq/878
Code:
Example on a Unix computer:
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Say you've got Calibre up and running, and that its database folder is ~/calibre/database.
Let's assume that you installed calibre2opds into /usr/local/calibre2opds.
Then, when you type the following command, the catalogs will be generated into ~/calibre/data/_catalog with the default options :
/usr/local/calibre2opds/bin/calibre2opds ~/calibre/data
If you want to change the default behavior, you'll have to use options ; issue the /usr/local/calibre2opds/bin/calibre2opds --help command to see which options are available.
as you can see, you do not have to set the catalog in the same folder than the database
I used the gui, that gives you the possibility to point the result to another folder than the one where calibre is located
reup